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Who discovered x-rays and when?

Wilhelm Conrad Roentgen on November 8, 1895


X-rays are a form of what kind of radiation?



Radiation that produces positively and negatively charged particles (ions) when passing through matter; the production of these ions is the event that may cause injury to normal biologic tissue
If electromagnetic radiation is of high enough frequency, it can transfer sufficient energy to some orbital electrons to remove them from the atoms to which they were attached; foundation of the interactions of x-rays with human tissue
Conversion of atoms to ions; makes tissues valuable for creating images but has the undesirable result of potentially producing some damage in the biologic material
Adding or losing an electron X-rays knock electrons out of orbit and change things on a cellular level that can hurt us or offspring



6 consequences of ionization in human cells

Creation of unstable atoms
Production of free electrons (Compton scatter produces recoil electrons)
Production of low energy x-ray photons
Creation of reactive free radicals capable of producing substances poisonous to the living cell
Creation of new biologic molecules detrimental to the living cell
Injury to the cell that may manifest itself as abnormal function or loss of function


The degree to which the diagnostic study accurately reveals the presence or absence of disease in the patient
Maximized when essential images are produced under recommended radiation protection guidelines
Provides the basis for determining whether an imaging procedure or practice is justified

Diagnostic efficacy


Who carries the responsibility for determining the medical necessity of a procedure for the patient?

The referring physician accepts basic responsibility for protecting the patient from radiation exposure that is not useful and relies on qualified imaging personnel who accept a portion of the responsibility for the patient's welfare by providing the high-quality imaging services


The intention behind these concepts of radiologic practice is to keep radiation exposure and consequent dose to the lowest possible level

Because no dose limits have been established for the amount of radiation that patients may receive for individual imaging procedures, this philosophy should be established and maintained and must show that we have considered reasonable actions that will reduce doses to patients and personnel below required limits

Radiation-induced cancer does not have a fixed threshold (a dose level below which individuals would have no chance of developing this disease); therefore, because it appears that no safe dose levels exist for radiation-induced malignant disease, radiation exposure should be kept low for all medical imaging procedures and this should serve as a guide to radiographers and radiologists for the selection of technical exposure factors

As low as reasonably achievable (ALARA)

Optimization for radiation protection (ORP)


3 basic principles/cardinal rules of radiation protection

  1. Time

  2. Distance

  3. Shielding


3 things the Radiation Safety Officer (RSO) is expressly charged by the hospital administration to be directly responsible for in the ALARA program

  1. Execution

  2. Enforcement

  3. Maintenance


The probability of injury, ailment, or death resulting from an activity

Risk (general)


The possibility of inducing a radiogenic cancer or genetic defect after irradiation

Risk (medical with reference to the radiation sciences)


A method that can be used to improve understanding and reduce fear and anxiety for the patient that compares the amount of radiation received over a given period of time based on an annual US population exposure of approximately 3 millisieverts per year

Background equivalent radiation time (BERT)


A subunit of the sievert (Sv) equal to 1/1000 of a sievert

Millisievert (mSv)


International System of Units (SI) unit of measure for the radiation quantity "equivalent dose"

Sievert (Sv)


A two phase radiation dose awareness and dose reduction program for patients through the process of education for these individuals, for the community, for health care workers employed in the medical imaging profession, and for physicians

Tools for Radiation Awareness and Community Education (TRACE) Program


2 phases of the TRACE program

  1. Formulating new policies and procedures to promote radiation safety and the implementation of patient and community education

  2. Technological enhancements


4 main components (technologic enhancements) of the TRACE program

  1. Embedded software capable of recording and reporting dose

  2. Timely notification of the patient and the referring physician when the radiation dose is greater than 3 Gy

  3. The substantial lowering of computed tomography (CT) doses

  4. Alterations to existing protocols


2 sources of radiation (both contribute a percentage of the total amount of radiation that humans receive during their lifetime)

  1. Natural

  2. Manmade


Radiation that is always present in the environment



Radiation created by humans for specific purposes



The ability to do work- that is, to move an object against resistance



Kinetic energy that passes from one location to another and can have many manifestations (many types of this exist)



The full range of frequencies and wavelengths of electromagnetic waves

Each frequency within this has a characteristic wavelength and energy Higher frequencies are associated with shorter wavelengths and higher energies; therefore, as the wavelength ranges from largest to smallest, frequencies and energy cover the corresponding smallest to largest ranges

Electromagnetic spectrum


The number of crests of a wave that move past a given point in a given unit of time; hertz (Hz), cycles per second



The distance between successive crests of a wave (meters)



A unit of energy equal to the quantity of kinetic energy an electron acquires as it moves through a potential difference of 1 volt

Electron volts (eV)


This form of radiation can travel through space in the form of a wave but can interact with matter as a particle of energy

Dual nature

Photons moving in waves and interactive with matter

Wave-particle duality


Bundles of energy



7 types of electromagnetic waves (longer wavelength, lower frequency, lower energy to shorter wavelength, higher frequency, higher energy)

  1. Radio waves

  2. Microwaves

  3. Infrared

  4. Visible light

  5. Ultraviolet (low and high energy)

  6. X-rays

  7. Gamma rays


2 parts the electromagnetic spectrum can be divided into

  1. Ionizing

  2. Nonionizing


3 forms of ionizing radiation

  1. X-rays

  2. Gamma rays

  3. High-energy ultraviolet radiation (energy higher than10 eV)


5 forms of non-ionizing radiation

  1. Low-energy ultraviolet

  2. Visible light

  3. Infrared rays

  4. Microwaves

  5. Radio waves


The amount of energy transferred to electrons by ionizing radiation

Radiation dose


Does not have the sufficient kinetic energy to eject electrons from the atom

Non-ionizing radiation


A radiation quantity used for radiation protection purposes when a person receives exposure from various types of ionizing radiation

Attempts to specify numerically the differences in transferred energy and therefore biologic harm produced by different types of radiation

Enables the calculation of effective dose (EfD)

SI unit: Sievert

Correlates the absorbed dose in biologic tissue with the type of energy of the radiation to which the human has been subjected (x-rays, gamma rays, etc.), applies only to ionizing types of radiation

Equivalent dose (EqD)


4 forms of particulate radiation

  1. Alpha particles

  2. Beta particles

  3. Neutrons

  4. Protons


Subatomic particles that are ejected from atoms at very high speeds

They possess sufficient kinetic energy to be capable of causing ionization by direct atomic collision

No ionization occurs when the subatomic particles are at rest

Particulate radiation


Emitted from nuclei of very heavy elements such as uranium and plutonium during the process of radioactive decay

Each contain two protons and two neutrons

Are simply helium nuclei (e.i., helium atoms minus their electrons)

Have a large mass (approximately 4 times the mass of a hydrogen atom) and a positive charge twice that of an electron

Weighting factor is 20 times higher than x-rays

Less penetrating than beta particles (fast electrons)

They lose energy quickly as they travel a short distance in biologic matter (i.e., into the superficial layers of the skin), so they are considered virtually harmless as an external source of radiation (a piece of ordinary paper can absorb them or function as a shield)

Can be very damaging as an internal source of radiation if emitted from a radioisotope deposited in the body (ex: in the lungs, they can be absorbed in the relatively radiosensitive epithelial tissue and are very damaging to that tissue)

Alpha particles/rays


Identical to high speed electrons except for their origin (emitted from within the nucleus of radioactive atoms that relieve their instability through the process of beta decay)

8,000 times lighter than alpha particles and have only one unit of electrical charge (-1) as compared with the alpha's two units of electrical charge (+2); will not interact as strongly with their surroundings as alpha particles and are therefore capable of penetrating biologic matter to a greater depth than alpha particles with far less ionization along their paths

With a lesser probability of interaction: can penetrate matter more deeply and therefore cannot be stopped by an ordinary piece of paper like an external alpha particle

For energies less than 2 millielectron volts, either a 1-cm thick block of wood or a 1-mm thick lead shield would be sufficient for absorption

Beta particles


Positively charged components of an atom

Have a relatively small mass that, however, exceeds the mass of an electron by a factor of 2800

Decide the type of element



Number of the protons in the nucleus of an atom constitutes this number

Atomic/Z number


The electrically neutral components of an atom and have approximately the same mass as a proton



Two atoms that have the same number of protons but a different number of neutrons in their nuclei (same element)



Takes into account the dose for all types of ionizing radiation (ex: alpha, beta, gamma, x-ray) to various irradiated organs or tissues in the human body (ex: skin, gonadal tissue, thyroid)

By including specific weighting factors for each of those body parts mentioned, this takes into account the chance or risk that each of those body parts will develop a radiation-induced cancer (somatic); in the case of the reproductive organs, the risk of genetic damage is considered

Because this includes all of the organ weighting factors, it represents the uniform whole-body dose that would give an equivalent biologic response or chance of cancer

Effective dose (EfD)


Produced when ionizing radiation penetrates body tissue and ejects electrons from the atoms composing the tissues

Biologic damage


Result of destructive radiation at the atomic level

Molecular change


Caused by molecular changes which leads to abnormal cell function or even entire loss of cell function

If excessive cellular damage occurs, the living organism will have a significant possibility of exhibiting genetic or somatic changes such as mutations, cataracts, leukemia, etc.

Cellular damage


Changes in the blood count that results from non-negligible exposure to ionizing radiation

Organic damage


2 sources of ionizing radiation that humans are exposed to

  1. Natural

  2. Manmade


Environmental sources of ionizing radiation

Natural (background) radiation


3 components of natural radiation

  • Terrestrial radiation (e.g., radon, thoron)

  • Cosmic radiation (solar and galactic, intensity increases with altitude)

  • Internal radiation from radioactive atoms (radionuclides)


Earth gives off this terrestrial radiation; 37% of natural background radiation exposure comes from this

Largest contributor to background radiation

In homes: crawl spaces, floor drains, sump pumps, and porous cement block foundations

The Environmental Protection Agency (EPA) considers this to be the second leading cause of lung cancer in the US



4 ways to indicate the amount of radiation received by a patient from diagnostic x-ray procedures

  1. Entrance skin exposures (including skin and glandular dose; greatest amount of radiation and why you don't want SOD to be small)

  2. Bone marrow dose

  3. Gonadal dose

  4. Fetal dose in pregnant women


4 ways to decrease patient dose

  1. Increase distance

  2. Shield

  3. Beam restriction

  4. High kVp, low mAs


2 technical factors

  1. Peak kilovoltage (kVp)

  2. Milliampere-seconds (mAs)


Controls the quality/penetrating power of the photons in the x-ray beam, and to some degree also affects the quantity or number of photons in the x-ray beam

Highest energy level of photons in the x-ray beam, determines what kind of interaction will occur (high or low energy)

Although all photons in a diagnostic x-ray beam don't have the same energy, the most energetic photons in the beam can have no more energy than the electrons that bombard the target

Peak kilovoltage (kVp)


Controls the quantity of radiation that is directed toward a patient during a selected x-ray exposure

Milliampere-seconds (mAs)

mA x s = mAs


If an interaction occurs, electromagnetic energy is transferred from the x-rays to the atoms of the patient's biologic material

A total loss of radiation energy



The amount of energy absorbed per unit mass

Absorbed dose (D)


3 factors affecting absorption

  1. Atomic number

  2. How tightly bound the atom's electrons are

  3. Thickness of part (ex: femur vs finger)


What reaction is the biggest concern for a technologist (occupational)?

Compton reactions produce scatter


What is the anode (target) made of?

Tungsten/tungsten rhenium alloy


2 reasons tungsten and tungsten rhenium alloy are used as target materials

  1. High melting points

  2. High atomic numbers (tungsten [74] and rhenium [75])


Why does the anode (target) need to have a high melting point?

99% of x-ray production is heat


Particles associate with electromagnetic radiation that have neither mass nor electric charge and travel at the speed of light

X-ray photons


Built-in filtration that results from the composition of the tube and housing

Inherent filtration


3 examples of inherent filtration

  • The thickness of the glass envelope of the tube

  • The dielectric oil that surrounds the tube

  • The glass window of the housing


Any filtration that occurs outside the tube and housing and before the image receptor

Added filtration


3 examples of added filtration

  1. A certain thickness of added aluminum in the collimator

  2. The collimator device

  3. The mirror is designed to reflect the collimator light to simulate the primary beam field size for positioning purpose


Removes low-energy x-ray photons, thereby decreasing patient dose; equal to the sum of inherent and added filtration that does not include any compound or compensating filters that may be added later

The percentage of photons attenuated decreases as photon energy increases, even when filtration is increased

Total filtration (permanent)


What is the amount of total filtration at 70 kVp?`

2.5 mm aluminum (Al) equivalence


The x-ray photon beam that emerges from the x-ray tube (source) and is directed toward the image receptor before they run into anything

Primary radiation/photons


For a typical diagnostic x-ray unit, the energy of the average photon in the x-ray beam is about what the energy of the most energetic photon?

One third, 33%


The reduction in the number of primary photons in the x-ray beam through absorption and scatter as a beam passes through the patient in its path (matter)

Any process decreasing the intensity of the primary photon beam that was directed toward a destination



A change of direction that may also involve a partial loss of radiation energy



Some primary photons will traverse the patient without interacting and reach the radiographic image receptor (IR)

Direct transmission


Other primary photons can undergo Compton and/or coherent interactions and as a result may be scattered or deflected with a potential loss of energy; such photons may still traverse the patient and strike the IR

Indirect transmission


2 most common methods used to limit the effects of indirectly transmitted x-ray photons

  1. Air gaps

  2. Radiographic grids


Photons that pass through the patient being radiographed and reach the IR

Exit/image-formation photons


5 types of interactions between x-radiation and matter

  1. Coherent

  2. Photoelectric absorption

  3. Compton scattering

  4. Pair production

  5. Photodisintegration


2 interactions important in diagnostic radiology

  1. Compton scattering

  2. Photoelectric absorption


3 other names for coherent scattering

  1. Classical scattering

  2. Elastic scattering

  3. Unmodified scattering


No ionization

A relatively simple process that results in no loss of energy as x-rays scatters

Occurs with low-energy photons

Because the wavelengths of both incident and scattered waves are the same, no net energy has been absorbed by the atom

Incoming and scattered photons have same energy; vibrates the atom and causes the photon to change direction with no loss of energy

The incoming low-energy x-ray photon interacts with an atom and transfers its energy by causing some or all of the electrons of the atom to vibrate momentarily

The electrons then radiate energy in the form of electromagnetic waves

These wave nondestructively combine with one another to form a scattered wave, which represents the scattered photon

Its wavelength and energy/penetrating power are the same as those as the incident photon

Generally, the emitted photon may change in direction less than 20 degrees with respect to the direction of the original photon

Coherent scattering (classical, elastic, or unmodified)


2 processes of coherent scattering (classical, elastic, or unmodified)

  1. Thompson

  2. Rayleigh


With what energy photons does coherent scattering (classical, elastic, or unmodified) occur?

Typically less than 10 keV


The most important mode of interaction between x-ray photons and the atoms of the patient's body for producing useful images; have to have this to have a picture

Makes image more black and white and responsible for patient dose

On encountering an inner-shell electron in the K or L shells, the incoming x-ray photon surrenders all its energy to the electron and the photon ceases to exist

The atom responds by ejecting the electron from its inner shell, thus creating a vacancy in that shell

To fill the opening, an electron from an outer shell drops down to the vacated inner shell by releasing energy in the form of a characteristic photon

Then, to fill the new vacancy in the outer shell, another electron from the shell next farthest out drops down and another characteristic photon is emitted, and so on until the atom regains electrical equilibrium

Have to give off energy when moving into the inner shell in the form of x-rays; don't go very far and are absorbed

Initial electrons and low energy x-rays are absorbed

Photoelectric absorption


An electron ejected from its inner shell during photoelectric absorption

Possesses kinetic energy equal to the energy of the incident photon less the binding energy of the electron shell

May interact with other atoms thereby causing excitation or ionization, until all its kinetic energy has been spent

Usually absorbed within a few micrometers of the medium through which it travels; in the human body, this energy transfer results in increased patient dose and contributes to biologic damage of tissues



An x-ray photon created by the electron transfer from one shell to another

As a result of the photoelectric interaction, a vacancy has been created in the inner shell of the target atom

For the ionized atom, this represents an unstable energy situation

The instability is alleviated by filling the vacancy in the inner shell with an electron from an outer shell, which spontaneously "falls down" into this opening

To do this, the descending electron must lose energy, that is, must pass from a less tightly bound atomic state (further from the nucleus) to a more tightly held state (closer to the nucleus)

The amount of energy loss involved is simply equal to the difference in the binding or "holding" energies associated with each electron shell

The "released" energy is carried off in the form of a photon

For a large atom such as those in lead, this energy can be in the kiloelectron volt range, whereas for the small or low atomic number atoms that are associated with the human body, the energy is on the order of 10 eV In general, ensuing vacancies in other electron shells are successively filled and associated characteristic photons are emitted until the atom achieves an electronic equilibrium

Low energy x-rays given off after a characteristic cascade

Characteristic photon/x-ray Fluorescent radiation


2 by-products of photoelectric absorption

  1. Photoelectrons (those induced by interaction with external radiation)

  2. Characteristic x-ray photons (fluorescent radiation)


When the energy of photoelectrons and characteristic x-ray photons is locally absorbed in human tissue, both the dose to the patient and the potential for biologic damage increases, decreases or remains the same?



2 things the probability of the occurrence of photoelectric absorption depends on

  1. Energy (E) of the incident x-ray photons

  2. Atomic (Z) number of the atoms comprising the irradiated object


Used in the digital environment to replace density (film)

The quantity of ionizing radiation received by a radiologic device and used to produce a viewable image

Image receptor (IR) exposure


A monitor function that can change the lightness or darkness of the image on a display monitor; the intensity of the display monitor's light emission controlled by the radiographer

Has no affiliation with the controlling factors of density (mA and exposure time [mAs])

Not interchangeable with density



Sets the midpoint of the range of densities visible on the image, controls computer screen brightness

Window level


Adjusting the window level, changing the brightness either to be increased or decreased throughout the entire range of densities



Increasing the window level on the displayed image (increased brightness) _______ the density on the hard copy image, whereas decreasing the window level on the monitor image (decreased brightness) _______ density on the hard copy

Decreases, increases


The greater the difference in the amount of photoelectric absorption, the ________ the contrast in the radiographic image will be between adjacent structures of differing atomic numbers



As absorption increases, the potential for biologic damage _______



The difference between adjacent densities; one of the properties that comprise visibility of detail

Radiographic contrast


The digital processing that produces changes in the range of density/brightness, which can be used to control contrast

Window width


Use of this may be needed to ensure visualization of tissues or structures that are similar in Z when mass density must be distinguished

Contrast media


Consists of solutions containing elements having a higher atomic number than surrounding soft tissue (e.g., barium or iodine based) that are either ingested or injected into the tissues or structures to be visualized

The high atomic number of the contrast media (barium = 56, iodine = 53) significantly enhances the occurrence of photoelectric interaction relative to similar adjacent structures that don't have contrast media

The inner-shell electrons of barium and iodine have a binding energy that is in the energy range of the x-ray photons that is most commonly used in general-purpose radiography (30 to 40 keV) meaning photoelectric absorption of the photons in the x-ray beam is greatly increased

Structures enhanced by this contrast appear lighter than adjacent structures that didn't receive the contrast (white)

Also leads to an increase in absorbed dose in the body structures that contain it

Positive contrast medium


Contrast mediums such as air or gas is also used for some radiologic examinations and result in areas of increased density on the completed image (black)

Negative contrast medium


3 other names for Compton scattering

  1. Incoherent scattering

  2. Inelastic scattering

  3. Modified scattering


What interaction is responsible for most of the scattered radiation produced during a radiographic procedure?

Compton (incoherent, inelastic, modified) scattering


An incoming x-ray photon interacts with a loosely bound outer electron of an atom of the irradiated object

On encountering the electron, the incoming x-ray photon surrenders a portion of its kinetic energy to dislodge the electron from its outer-shell orbit, thereby ionizing the biologic atom

The freed electron possesses excess kinetic energy and is capable of ionizing other atoms

It loses its kinetic energy by a series of collisions with nearby atoms and finally recombines with an atom that needs another electron; this usually occurs within a few micrometers of the site of the original interaction

The incident x-ray photon that surrendered some of its kinetic energy to free the loosely bound outer-shell electron from its orbit continues on its way but in a new direction has the potential to interact with other atoms either by the process of photoelectric absorption or scattering; it may also emerge from the patient, in which case it may contribute to degradation of the radiographic image by creating an additional, unwanted exposure (radiographic fog), or in fluoroscopy, it may exposure personnel who are present in the room to scattered radiation

onizing, occurs in the body

X-ray photon has more energy going in than when it leaves the atom

Increases as kVp increases

Produces scatter, no diagnostic value

Compton (incoherent, inelastic, modified) scattering


The dislodged electron resulting from Compton scattering

Compton scattered, secondary, or recoil electron


The incident x-ray photon that surrendered some of its kinetic energy to free the loosely bound outer-shell electron from its orbit continues on its way but in a new direction

Compton scattered photon


In diagnostic radiology, the probability of occurrence of Compton scattering relative to that of the photoelectric interaction __________ as the energy of the x-ray photon increases



Who was the first person to die from x-rays?

Clarence Madsen Dally


Radiation exposure received by radiation workers

Occupational radiation


Biologic effects in humans caused by exposure to ionizing radiation, which appeared within minutes, hours, days, or weeks of the time of radiation exposure

Early deterministic somatic effects


Biologic response whose severity varies with radiation dose; determined by the dose threshold



2 effects of ionizing radiation that appear months or years after exposure

Late deterministic somatic effects
Late stochastic effects


Nonthreshold, randomly occurring biologic effects of ionizing radiation
Effects can result from relatively low radiation exposure, and can take a long time before they're demonstrated; the probability of occurrence depends on the radiation dose and type and energy of the radiation which means that some radiations are more biologically efficient for causing damage than others for a given dose
Probability or frequency of the biologic response to radiation as a function of radiation dose
Disease incidence increases proportionally with dose, and there is no dose threshold



Effect of radiation that is seen in an individual and in subsequent unexposed generations

Genetic/heritable effects


8 early deterministic somatic effects

Diffuse redness of the skin
Loss of hair
Intestinal disorders
Blood disorders
Shedding of the outer layer of the skin


6 late deterministic somatic effects

Cataract formation
Organ atrophy
Loss of parenchymal cells
Reduced fertility


2 late stochastic effects

Genetic (hereditary) effects


What amount of radiation is considered completely safe?

No amount


Sum of the weighted equivalent doses doses for all irradiated tissues or organs
A measure of the overall risk arising from the irradiation of biologic tissue and organs that takes into consideration the exposure to the entire body based on the energy deposited in biologic tissue by ionizing radiation
Incorporates both the effect of the type of radiation used and the variability in radiosensitivity of the specific organ or body part irradiated through the use of appropriate weighting factors; these factors determine the overall harm to those biologic components and the risk of developing a radiation induced cancer, or, for the reproductive organs, the risk of genetic damage
Attempts to take into account the different levels of radiation effects on the parts of the body that are being irradiated to arrive at an index of overall harm to a human by beginning with EqD and then incorporating modifying or weighting factors which correspond to the relative degrees of radiosensitivity of various organs and tissues
The quantity that summarizes the potential for biologic damage to a human from exposure to ionizing radiation
Accounts for the risk to the entire organism brought on by irradiation of individual tissues and organs

Effective dose (EfD)


2 things EfD takes into account

The type of radiation (e.g., x-radiation, gamma, neutron)
The variable sensitivity of the tissues exposed to radiation


Provides a common scale whereby varying degrees of biologic damage caused by equal absorbed doses of different types of ionizing radiation can be compared with the degree of biologic damage caused by the same amount of radiation

Sievert (Sv)


Radiation quantity "that expresses the concentration of radiation delivered to a specific area, such as the surface of the human body"
The amount of ionizing radiation that may strike an object such as the human body when in the vicinity of a radiation source
Amount of radiation in air
When a volume of air is irradiated with x-rays or gamma rays, the interaction that occurs between the radiation and neutral atoms in the air causes some electrons to be liberated from those air atoms as they are ionized. Consequently, the ionized air can function as a conductor and carry electricity because of the negatively charged free electrons and positively charged ions that have been created. As the intensity of x-ray exposure of the air volume increases, the number of electron-ion pairs produced also increases. Thus the amount of radiation responsible for the ionization of a well-defined volume of air may be determined by measuring the number of electron-ion pairs or charged particles in that volume of air; radiation ionization in the air
A measure of ionization in air and not in other tissue

Exposure (X)


The amount of energy per unit mass absorbed by an irradiated object
This absorbed energy is responsible for any biologic damage resulting from exposure of the tissues to radiation; for this reason, this may be used to indicate the amount of ionizing radiation a patient receives during a diagnostic imaging procedure
The deposition of energy per unit mass in the patient's body tissue from exposure to ionizing radiation
As ionizing radiation passes through an object such as a human body, some of the energy of that radiation is transferred to that biologic material; it is actually absorbed by the body and stays within it
Some structures in the body absorb more radiant energy than others

Absorbed dose (D)


The product of the average absorbed dose in a tissue or organ in the human body and its associated radiation weighting factor (WR) chosen for the type and energy of the radiation in question
A radiation quantity used for radiation purposes when a person receives exposure from various types of ionizing radiation; serves as a measure of absorbed energy resulting from ionization
Attempts to take into account the potential variation in biologic harm that is produced by different kinds of radiation; both the type and energy of the radiation are considered
Takes into account the weighting factor for the radiation you got (ex: x-ray = 1 versus alpha particle = 20)

Equivalent dose (EqD)


Basic unit of electrical charge; represents the quantity of electrical charge flowing past a point in a circuit in 1 second when an electrical current of 1 ampere is used

Coulomb (C)


SI unit of electrical current; number of flowing electrons
A unit of electric current equal to a flow of one coulomb per second

Ampere (A)


SI exposure unit equal to an electrical charge of 1 C produced in a kilogram of dry air by ionizing radiation
Used for x-ray calibration because x-ray output intensity is measures directly with an ionization chamber; also used to calibrate radiation survey equipment

Coulombs per kilogram (C/kg)


Kinetic energy released in a unit mass (kilogram) of air
SI quantity that can be used to express radiation concentration transferred to a point, which may be at the surface of a patient's or radiographer's body
X-ray tube output and inputs to image receptors are sometimes described in this
Actually denotes a calculation of radiation intensity in air
Replacing the traditional quantity, exposure
Amount of radiation coming out of the tube

Air kerma
"Kinetic energy released in material"
"Kinetic energy released in matter"
"Kinetic energy released per unit mass"


What is the unit of kerma?

Gray (Gy)


Kinetic energy released in a unit mass of tissue

Tissue kerma


What is the unit of tissue kerma?

Gray (Gyt)


The sum total of air kerma over the exposed area of the patient's surface; a measure of the amount of radiant energy that has been thrust into a portion of the patient's body surface
Modern radiographic and fluoroscopic units have incorporated units have incorporated an ability to determine the entire amount of energy delivered to the patient by the x-ray beam
Ability to determine the entire amount of energy delivered to the patient by the x-ray beam
Ex: how much radiation goes to the 10 x 12 area you've collimated to

Dose area product (DAP)


3 things the amount of energy absorbed by a structure depends on

Atomic number (Z) of the tissues comprising the structure
The mass density of the tissue (kg/m^3)
Energy of the incident photon (low-energy photons are more easily absorbed in a material such as biologic tissue than are high-energy photons)


Absorption _______ as atomic number and mass density increase and also as photon energy decreases



"Composite"/weighted average of the atomic numbers of the many chemical elements comprising the tissue

Effective atomic number (Zeff)


What is the effective atomic number of bone and soft tissue?

Bone: 13.8
Soft tissue: 7.4


Bone absorbs ______ ionizing radiation than dose soft tissue in the diagnostic energy range of 23-150 kilovolts peak (kVp), because the photoelectric process for bone is the dominant mode of energy absorption within this range



The probability of photoelectric interaction strongly depends on the atomic number of the irradiated material; the _______ the atomic number of material, the greater is the amount of energy absorbed by that material



The amount of photoelectric absorption decreases and the amount of Compton scattering relative to the photoelectric interaction increases as the energy of the x-ray beam __________; the amount of Compton scattering in a material does not depend on the atomic number of the material



As energy increases, the difference in the amount of absorption between any two tissues of different atomic number ____________



At all energies, mass density always has an effect on absorption; this effect is linear and ________ proportional



SI unit of absorbed dose; an energy absorption of 1 Joule (J) per kilogram (kg) of matter in the irradiated object

Gray (Gy)


The work done or energy expended when a force of 1 newton (N) acts on an object along a distance of 1 meter (m)

Joule (J)


3 prefixes, subunits, symbols, fractions and factors

Centi-, c, 1/100, 10^-2
Milli-, m, 1/1000, 10^-3
Micro-, u, 1/1,000,000, 10^-6


How do you convert grays to milligrays?

Number of grays (Gy) x 1000 = number of milligrays (mGy)


The total amount of radiant energy transferred by ionizing radiation to the body during a radiation exposure
Determined by the produce of the exposure value (R) and the size of the area (cm^2) that receives the total amount of radiation delivered

Surface integral dose (SID)
Historically known as exposure area product


Equal absorbed doses of different types of radiation produce ________ amounts of biologic damage



An adjustment multiplier that has been used in the calculation of dose equivalence to specify the ability of a dose of any kind of ionizing radiation to cause biologic damage

Quality factor (Q)


What is the weighting factor of x-radiation and alpha particles?

X-ray: 1
Alpha: 20


Radiation with a high LET transfers a _______ amount of energy into a small area and can therefore do more biologic damage than radiation with a low LET; as a result, a high-LET radiation has a quality factor that is ________ than the quality factor for a low-LET radiation

Large, greater


Do you want a high or low LET?



Dimensionless factor (multiplier) used for radiation protection purposes to account for differences in biologic impact among various types of ionizing radiation
Must be used to determine EqD
Places risks associated with biologic effects on a common scale
Type of radiation

Radiation weighting factor (WR)


SI unit for EqD

Sievert (Sv)


Equation for EqD

EqD = absorbed dose (D) x radiation weighting factor (WR)
sV = Gy x WR


How do you convert sieverts to millisieverts?

Number of millisieverts (mSv) = number of sieverts (Sv) x 1000


2 examples of stochastic effects

Genetic/hereditary abnormalities


Equation of effective dose (EfD)

EfD = absorbed dose (D) x radiation weighting factor (WR) x tissue weighting factor (WT)


Weighting factor that takes into account the relative detriment to each specific organ and tissue; a conceptual measure for the relative risk associated with irradiation of different body tissues to account for the carcinogenic sensitivity of each organ
Value that denotes the percentage of the summer stochastic (cancer plus genetic) risk stemming from irradiation of tissue (T) to the all-inclusive risk, when the entire body is irradiated in a uniform fashion

Tissue weighting factor (WT)


What tissue is most and least radiosensitive?

Most: gonads
Least: Bone surface


Unit of EfD

Sieverts or millisieverts


Surface of the patient that is toward the x-ray tube exposed to the unattenuated primary beam of x-rays
Where dose to the patient is the highest

Entrance skin surface


Used to describe radiation exposure of a population or group from low doses of different sources of ionizing radiation
Determines as the product of the average EfD for an individual belonging to the exposed population or group and the number of persons exposed
Used in radiation protection to describe internal and external dose measurements

Collective effective dose (ColEfD)


The sum of effective dose equivalent from external radiation exposure and committed effective dose equivalent (CEDE) from internal radiation exposures
Designed to take into account all possible sources of radiation exposure
Radiation dosimetry quantity defined to monitor and control human exposure to ionizing radiation

Total effective equivalent dose (TEDE)


When is exposure monitoring or personnel required?

Whenever radiation workers are likely to risk receiving 10% or more of the annual occupational EfD limit of 50 mSv (5 rem) in any single year as a consequence of their work related activities


In keeping with ALARA, at what limit do most health care facilities issue dosimetry devices?

When personnel could receive approximately 1% of the annual occupational EfD limit in any month; approximately 0.04 mSv (4 mrem)


5 personnel monitoring devices currently available

Optically stimulated luminescence (OSL) dosimeter
Extremity dosimeter (thermoluminescent dosimeter (TLD) ring)
Film badge
Thermoluminescent dosimeter (TLD)
Pocket ionization chamber (pocket dosimeter)


Where should the personnel dosimeter be placed during routine radiographic procedures when a protective apron is not being used?

Attached to the clothing on the front of the body at collar level


Where should the personnel dosimeter be placed when a protective apron is worn (fluoroscopy, surgery, and special radiographic procedures)?

Outside the apron at collar level on the anterior surface of the body


The unprotected head, neck, and lenses of the eye receive how many times more exposure than the protected body trunk?



Where should the personnel dosimeter be placed as a second monitor when a protective apron is worn (during lengthy interventional fluoroscopy procedures [e.g., cardiac catheterization])?

The first/primary dosimeter is to be worn outside the protective apparel at collar level; the second should be worn beneath a wraparound-style lead apron at waist level to monitor the approximate equivalent dose to the lower body trunk


Where should the personnel dosimeter be placed as a monitor for the embryo-fetus?

The primary dosimeter is to be worn at collar level; the second is worn at the abdomen


Worn as a second monitor when performing radiographic procedures that require the hands to be near the primary x-ray beam; ring that can be used to monitor the equivalent dose to the hands
Badge cover contains information such as the account number, participant's name and number, wear date, indication of hand (right or left), size, and reference number; even though these badges are worn under gloves to avoid contamination, such extremity monitors are laser-etched to ensure the retention of permanent identification
The reusable element of the dosimeter is encapsulated with an engraved cover

Extremity dosimeter (thermoluminescent dosimeter [TLD] ring badge)


4 types of personnel dosimeters used to measure individual exposure of the body to ionizing radiation

Optically stimulated luminescence (OSL) dosimeter
Film badge
Thermoluminescent dosimeter (TLD)
Pocket ionization chamber (pocket dosimeter)


What is the most common type of device used for monitoring of occupational exposure in diagnostic imaging?

Optically stimulated luminescence (OSL) dosimeter


What does the OSL dosimeter contain?

A thin layer of aluminum oxide (Al2O3) detector


How long can the OSL dosimeter be worn, and how long is it commonly worn?

It can be worn for up to 1 year; it is common practice to wear it for a period of 1-3 months


3 materials the 3 different filters incorporated into the detector pack of the OSL dosimeter are made of respectively

Aluminum (Al)
Copper (Cu)


3 different energy ranges of the OSL dosimeter that physically correlate with different penetration depths and therefore different effective radiation energies

"Deep" (most penetrating)
"Shallow" (skin)


Which dosimeter can be worn the longest?

Optically stimulated luminescence (OSL) dosimeter


Which dosimeter can read the lowest dose?

Optically stimulated luminescence (OSL) dosimeter


At what degree can the OSL dosimeter provide an accurate reading?

1 mrem (10 uSv) for x-ray photons with energies ranging from 5 keV to greater than 40 MeV


Serves as a basis for comparison with remaining dosimeters after they have been returned to the company for processing
Supposed to be kept in a radiation-free area within an imaging facility so its optical density reading is zero

Control monitor


7 advantages of the OSL dosimeter

Lightweight, durable, and easy to carry Contains an integrated, self-contained, preloaded packet Color-coded, contains graphic formats, and body location icons that provide easy identification Not affected by heat, moisture, and pressure Offers complete reanalysis Increased sensitivity, providing accurate readings as low as 10 uSv (1 mrem) for x-ray photons with energies from 5 keV-40 MeV Can be worn for longer periods of time (up to 1 year)


3 disadvantages of the OSL dosimeter

Occupational radiation exposure is recorded only in the body area where the device is worn (not close to reproductive organs)
Exposure cannot be determined on the day of occurrence
Not an efficient monitoring device if it is not worn


Dosimeter that records whole-body radiation exposure accumulated at a low rate over a long period of time

Film badges


3 parts the film badge is composed of

Durable, lightweight plastic film holder
Assortment of metal filters
Film packet


What are the metal filters inside the plastic holder of the film badge made of?

Aluminum or copper


What dose ranges are film badges sensitive to?

As low as 0.1 mSv (10 mrem) to as high as 5000 mSv (500 rem); doses less than 0.1 mSv (10 mrem) are not usually detected and are reported as minimal (M) on a personnel monitoring report


Degree of blackening



An instrument that measures occupational exposure by comparing optical densities of exposed film badge (dosimetry) films



5 advantages of the film badge

Main: permanent legal record of personnel exposure
Used to record exposure to x-radiation, gamma radiation, and all but very low-energy beta radiation in a reliable manner
Can discriminate among the types of radiation and the energies of these radiations
Mechanical integrity


3 disadvantages of film badges

Temperature and humidity extremes or wetting can cause fogging of the dosimetry film over long periods of time
A radiation worker's exposure cannot be determined on the day of occurrence
Can be worn for one month before being read


How long can the film badge be worn for personnel monitoring before it is read?

1 month


What is the film badge dosimeter sensitivity?

Most sensitive to photons having an energy level of 50 keV; for values above and below this energy range, dosimetry film sensitivity decreases


What is the sensing material of the thermoluminescent dosimeter (TLD)?

Crystalline form (powder or, more frequently, small chips) of lithium fluoride (LiF)


4 advantages of the TLD

The LiF crystals interact with ionizing radiation as human tissue does, hence this monitor determines dose more accurately
Exposures as low as 5 mR (1.3 x 10^-6 C/kg) can be measured precisely
Humidity, pressure, and normal temperature changes don't affect it
After the TLD reading has been obtained, the crystals can be reused, making it somewhat cost effective


What is the sensitivity of the TLD?

Exposures as low as 5 mR (1.3 x 10^-6 C/kg) can be measured precisely


3 disadvantages of the TLD

High cost (twice the cost of a film badge service)
Can be read only once/can't be reevaluated; the readout process destroys the stored information
The calibrated dosimeters must be prepared and read with each group or batch


What is the most sensitive type of personnel dosimeter

Pocket ionization chamber (pocket dosimeter)


To what exposure range are pocket chambers used in medical imaging sensitive to?

0-5.2 x 10^-5 C/kg (0-200 mR)


What is an advantage of the pocket ionization chamber?

Provide immediate exposure readouts


3 disadvantages of the pocket ionization chamber

Fairly expensive
Inaccurate readings
No permanent legal record


3 different gas-filled radiation detectors that serve as field instruments

Ionization chamber-type survey instrument ("cutie pie")
Proportional counter
Gieger-Muller (GM) detector


Rate meter device (for exposure rate) used for area surveys and an accurate integrating or cumulative exposure instrument; it measures x-radiation and gamma radiation, and, if equipped with a suitable window, it can also record beta radiation

Ionization chamber survey meter (cutie pie)


What ranges of radiation intensity can the ionization chamber survey meter (cutie pie) measure?

1 mR/hr-several thousand milliroentgens per hour (10-several thousand micrograys per hour)


What is the greatest amount of radiation that can come out of the x-ray tube?

1 mR/hr (10 micrograys per hour)


What is the radiation survey instrument of choice when determining exposure rates from patients?

Ionization chamber survey meter (cutie pie)


3 disadvantages of the ionization chamber survey meter (cutie pie)

Delicate detector unit
Without adequate warmup time, its meter drifts and produces an inaccurate reading
Cannot be used to measure exposures produced by typical diagnostic procedures because the exposure times are too short to permit the meter to respond appropriately


Survey instrument that serves no useful purpose in diagnostic imaging; generally used in a laboratory setting to detect alpha and beta radiation and small amounts of other types of low-level radioactive contamination
Can discriminate between alpha and beta particles

Proportional counter


Serves as the primary potable radiation survey instrument for area monitoring in nuclear medicine facilities
Sensitive enough to detect particles or photons

Geiger-Muller (GM) detector


2 disadvantages of the GM detector

The meter reading is not independent of the energy of the incident photons meaning that photons of widely different energies cause the instrument to respond quite differently
Likely to saturate or jam when placed in very high-intensity radiation area, giving a false reading


A science that explores living things and life processes



Basic units of all living matter and essential for life; fundamental component of structure, development, growth, and life processes in the human body
Human body composed of trillions of these that exist in a multitude of different forms



4 functions the cells perform for the body

Conduction of nerve impulses
Contraction of muscles
Support of various organs
Transportation of body fluids such as blood


Chemical building material for all living things; living contents of cell



3 cell chemical components

Organic compounds
Inorganic compounds


3 processes the protoplasm carries on

Complex process of metabolism
Reception and processing of food and oxygen
Elimination of waste products


The breaking down of large molecules into smaller ones
Enables the cell to perform the vital functions of synthesizing proteins and producing energy



2 things protoplasm consists of that are either dissolved or suspended in water

Organic compounds
Inorganic compounds


Those compounds that contain carbon, hydrogen, and oxygen

Organic compounds


Compounds that do not contain carbon, occur in nature independent of living things

Inorganic compounds


4 primary elements that comprise protoplasm



2 elements carbon, hydrogen, oxygen and nitrogen combine with to form the essential major organic compounds



4 major classes of organic compounds that compose the cell

Nucleic acids


2 most important inorganic compounds

Mineral salts/electrolytes


8 essential functions of water

Acts as the medium in which acids, bases, and salts are dissolved
Functions as a solvent by dissolving chemical substances in the cell
Functions as a transport vehicle for material the cell uses or eliminates
Maintains a constant body core temperature of 98.6 F (37 C)
Provides a cushion for vital organs such as the brain and lungs
Regulates concentration of dissolved substances
Lubricates the digestive system
Lubricates skeletal articulation (joints)


What is the most abundant inorganic compound in the body?



3 ways in which mineral salts are of vital importance in sustaining cell life

Help produce energy
Aid in the conduction of nerve impulses
Responsible for the prevention of muscle cramping


Basic constituent of all organic matter



3 elements carbon combines with to make life possible



Most elementary building blocks of cells; formed when amino acids combine into long, chainlike molecular complexes



3 functions proteins are essential for

Construction of new body tissue
Repair of injured or debilitated tissue


Provide the body with its shape and form and are a source of heat and energy
Ex: those found in muscle

Structural proteins


Function as organic catalysts
Control the cell's various physiologic activities
Cause an increase in cellular activity that in turn causes biochemical reactions to occur more rapidly to meet the needs of the cell; proper cell function depends on this
Initiate vital chemical reactions within the cell at the appropriate time

Enzymatic proteins/"enzymes"


Enzymes that can mend damages molecules and are therefore capable of helping the cell to recover from a small amount of radiation-induced damage; work effectively in both the diagnostic and therapeutic range
If the radiation damage is excessive because of the delivered equivalent dose, the damage will be too severe for these enzymes to have a positive effect; ex: atomic bond

Repair enzymes


Chemical secretions manufactured by various endocrine glands and carried by the bloodstream to influence the activities of other parts of the body; regulate body functions such as growth and development
Ex: these produced by the thyroid gland located in the neck control metabolism throughout the body



Protein molecules produced by B lymphocytes (specialized cells in the bone marrow)
Produced when other lymphocytes in the body (T lymphocytes) detect the presence of molecules that do not belong to the body
Once the skin has been penetrated, this is the body's primary defense mechanism against infection and disease



Foreign objects (ex: bacteria, flu, viruses), molecules that do not belong to the body



What is the primary energy source for the cell?



6 functions that lipids perform for the body

Acts as a reservoir for the long-term storage of energy
Insulate and guard the body against the environment
Support and protect organs such as the eyes and kidneys
Provide essential substances necessary for growth and development
Lubricate the joints
Assist in the digestive process


2 types of nucleic acids that are contained in cells and important to human metabolism

Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)


The master chemical in the nucleus
Contains all the information the cell needs to function
Carries the genetic information necessary for cell replication
Controls cell division
Determines a persons characteristics by regulating the sequence of amino acids in the person's constituent proteins during synthesis of these proteins

Deoxyribonucleic acid (DNA)


Plays an essential part in the translation of genetic information from DNA into protein products by functioning as a messenger between DNA and the ribosomes, where synthesis occurs
Carrier of information because DNA is stuck in the nucleus

Ribonucleic acid (RNA)


3 types of ribonucleic acid (RNA)

Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)


How many chromosomes does a normal human being have in each somatic (nonproductive) cell?

46 different chromosomes (23 pairs)


How many chromosomes do the reproductive/germ cells have?

Reproductive/germ cells exist singly, thus each has only 23 chromosomes, which pair up to form 46 chromosomes when a sperm fertilizes an egg


Segments of DNA that serve as the basic units of heredity
Control the formation of proteins in every cell through the intricate process of genetic coding



The total amount of genetic material (DNA) contained within the chromosomes of a human being

Human genome


The process of locating and identifying the genes in the genome



3 inorganic compounds



Hydrogen-containing compounds that can attack and dissolve metal
Ex: HNO3 (nitric acid)



Alkali or alkaline earth compounds that can neutralize acids
Ex: Mg(OH)2 (milk of magnesia)



Chemical compounds resulting from the action of an acid and a base on each other
Chemically they are substances that become ions in solution and acquire the capacity to conduct electricity
Present in the human body, and the balance in our bodies is essential for normal function of our cells and organs
Keep the correct proportion of water in the cell



2 most important inorganic substances

Mineral salts


What is the primary inorganic substance contained in the human body?

Water, it is imperative for the correct amount of water in a cell to be maintained


What percentage of the body weight does water comprise?



2 functions of water within the cell

The medium in which the chemical reactions that are the bases of metabolic activities occur
Acts as a solvent, keeping compounds dissolved so that they can more easily interact and their concentration may be regulated


4 functions of water outside the cell

Functions as a transport vehicle for material the cell uses or eliminates
Responsible for maintaining a constant body core temperature of 98.6 F (37 C)
Protects organs such as the brain and lungs
Regulates concentration of dissolved substances
Lubricates the digestive system and skeletal articulations


What is the constant body core temperature?

98.6 F (37 C)


3 things mineral salts are necessary for

Proper cell performance
Creation of energy
Conduction of impulses along nerves (wouldn't know if you're touching or moving anything without it)


2 types of cell divisions that occur in the body



A parent cell divides to form two daughter cells identical to the parent cell resulting in an approximately equal distribution of all cellular material between the two daughter cells
The division and last phase of the cellular life cycle
Somatic cells divide
Process in which the nucleus first divides, followed by the division of the cytoplasm

Mitosis (M)


Special type of cell division that reduces the number of chromosomes in each daughter cell to half the number of chromosomes in the parent cell
Genetic/germ cells undergo a process of reduction division of half



Female germ cell



Male germ cell



3 main parts the cell contains

Cell membrane


4 components of the normal cell

Cell membrane
Cytoplasmic organelles


6 cytoplasmic organelles

Endoplasmic reticulum
Golgi apparatus/complex


Frail, semipermeable, flexible structure encasing and surrounding the human cell
Allows penetration only by certain types of substances and regulates the speed at which these substances travel within the cell; plays a primary role in the cell's transport system

Cell membrane


The protoplasm that exists outside the cell's nucleus
Makes up the majority of the cell and contains large amounts of all the cell's molecular components (not DNA)
All cellular metabolic functions occur in this



6 things the cytoplasm is composed of

Water (primary)


4 major tasks of the cytoplasm

Accepts and builds up unrefined materials and assembles from these materials new substances such as carbohydrates, lipids, and proteins
Packages substances for distribution to other areas of the cell or to various sites in the body through the circulation
Eliminates waste products


Contains all the miniature cellular components that enable the cell to function in a highly organized manner; little organs of cells
Together these structures perform the major functions of the cell in a systemized way
DNA determines each function
mRNA carries the DNA code from the nucleus into the cytoplasm

Cytoplasmic organelles


4 things the cytoplasmic organelles consist of

Tiny tubules


Vast, irregular network of tubules and vesicles spreading and interconnecting in all directions throughout the cytoplasm
Enables the cell to communicate with the extracellular environment and transfer food and molecules from one part of the cell to another; functions as the highway system of the cell
Ex: mRNA travels from the nucleus to different locations in the cytoplasm; lipids and proteins are routed into and out of the nucleus through the tubular network

Endoplasmic reticulum (ER)


Minute vesicles that extend from the nucleus to the cell membrane
Consist of tubes and a tiny sac located near the nucleus; unites large carbohydrate molecules and the combines them with proteins to form glycoproteins
When the cell manufactures enzymes and hormones, this concentrates, packages, and transports them through the cell membrane so that they can exit the cell, enter the bloodstream, and be carried to the areas of the body where they are required

Golgi apparatus/bodies/complex


Large, double-membranous, oval or bean-shaped structure that functions as the "powerhouse" of the cell because they supply the energy for cells
Contain highly organized enzymes in their inner membranes that produce this energy for cellular activity by breaking down nutrients through the process of oxidative metabolism



Small, pealike sacs or single-membrane spherical bodies that are great importance for digestion within the cytoplasm
Contain a group of different digestive enzymes that target proteins
Primary function: the breaking down of unwanted large molecules that either penetrate into the cell through microscopic channels or are drawn in by the cell membrane itself



Very small spherical organelles that attach to the ER
"Protein factories"; their job is to manufacture (synthesize) the various proteins that cells require by using the blueprints provided by the mRNA



Separated from the other parts of the cell by a double-walled membrane, this forms the heart of the living cell
Spherical mass of protoplasm (nucleoplasm) that contains the genetic material, DNA, and protein
Controls cell division and multiplication and the biochemical reactions that occur within the cell



A protein machine that segregates chromosomes to two daughter cells during the cell division
Delicate fibers that are attached to the centrioles and extend from one side of the cell to the other across the equator of the cell

Mitotic spindle


4 distinct phases of the cellular life cycle that are identifiable

M (mitosis phase)
G1 (pre-synthesis phase)
S (synthesis phase)
G2 (post-DNA synthesis phase)


4 subphases mitosis (M) can be divided into



3 intervals of interphase



The period of cell growth that occurs before actual mitosis; cells are not yet undergoing division during this phase

Interphase (resting)


The earliest phase among reproductive events; the gap in the growth of the cell that occurs between mitosis and DNA synthesis
A form of RNA is synthesized in the cells that are to reproduce; this RNA is needed before actual DNA synthesis can efficiently begin

G1 (pre-synthesis phase)


Each DNA molecule contained within the chromosome is first copied (replicated) and then is divided into two individual sister chromatids, each containing DNA molecules
Each of these identical sister chromatids is now one half of the replicated chromosome
The chromatids will join together to form another chromosome by the end of this phase
A chromosome consists of two copies of the DNA that is contained in each chromatid
Chromosome reproduces itself and splits longitudinally, thus forming two sister chromatids attached to each other at the centromere

S (synthesis phase)


Highly coiled strand; one of the two duplicated portions of DNA in a replicated chromosome that appear during cell division



Cells manufacture certain proteins and RNA molecules need to enter and complete the next mitosis
When this phase is complete, cells enter the first phase of mitosis (prophase)

G2 (post-DNA synthesis phase)


The first phase of cell division
The nucleus enlarges, the DNA complex (the chromatid network of threads) coils up more tightly, and the chromatids become more visible
Chromosomes enlarge, and the DNA begins to take structural form
The nuclear membrane disappears, the centrioles migrate to opposite side of the cell and begin to regulate the formation of the mitotic spindle



Phase when cells are most radiosensitive
At the beginning of this phase, the mitotic spindle forms between the centrioles
Each chromosome, which now consists of two chromatids, lines up in the center/equator of the cell attached by its centromere to the mitotic spindle and forms the equatorial plate
The centromeres duplicate, and each chromatid attaches itself individually to the spindle
At the end, the chromatids are strung out along the mitotic spindle



The duplicate centromeres migrate in opposite directions along the mitotic spindle and carry the chromatids to opposite sides of the cell; the cell is now ready to begin the last phase of division



The chromatids undergo changes in appearance by uncoiling and becoming long, loosely spiraled threads
Simultaneously, the nuclear membrane forms anew, and two nuclei (one for each new daughter cell) appear
The cytoplasm also divides (cytokinesis) new the equator of the cell to surround the new nucleus
After this cell division completes, each daughter cell has a complete cell membrane and contains exactly the same amount of genetic material (46 chromosome) as the parent cell



Fertilized ovum (zygote) splits after fertilization and two separate offspring develop

Identical twins


More than one ootid is available for fertilization, and the separate ootids are fertilized by separate spermatozoa

Fraternal twins


More than two dizygotic twins

Polyzygotic siblings


3 important concepts that help us understand the way ionizing radiation causes injury and how the effects may vary in biologic tissue

Linear energy transfer
Relative biologic effectiveness
Oxygen enhancement ratio


The average energy deposited per unit length of track by ionizing radiation as it passes through and interacts with a medium along its path
A very important factor in assessing potential tissue and organ damage from exposure to ionizing radiation

Linear Energy Transfer (LET)


What is the unit of LET?



2 radiation categories according to LET

Low-linear energy transfer radiation
High-linear energy transfer radiation (more damage)


When low-LET radiation interacts with tissue it causes damage to a cell primarily through an _______ action that involves the production of molecules called __________ (bad for you)

Indirect, free radicals


2 examples of low LET radiation

Gamma rays


6 examples of high LET radiation

Alpha particles
Beta particles
Ions of heavy nuclei
Charged particles released from interactions between neutrons and atoms
Low-energy neutrons


High LET = _______ RBE



Because low-LET radiation generally causes sublethal damage to DNA, ______________ can usually reverse the damage

Repair enzymes


Describes the relative capabilities of radiation with differing LETs to produce a particular biologic reaction

Relative biologic effectiveness (RBE)


The ratio of the radiation dose required to cause a particular biologic response of cells or organisms in any oxygen-deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions

Oxygen enhancement ratio (OER)


Oxygenated state



Low oxygen



When irradiated in an aerobic state, biologic tissue is more sensitive to radiation than when it's exposed to radiation under anoxic conditions

Oxygen effect


In living systems, biologic damage resulting from exposure to ionizing radiation may be observed on 3 levels



Any visible radiation-induced injuries of living systems at the cellular or organic level always begin with damage at this level
Results in the formation of structurally changed molecules that may impair cellular functioning

Molecular level


If radiation damages the germ cells, the damage may be passed on to future generations in this form

Genetic mutations


2 classifications of ionizing radiation interaction on a cell

Direct action (e.g., in DNA)
Indirect action (e.g., in H2O)


Biologic damage occurs as a result of ionization of atoms on essential molecules that may potentially cause these molecules to become inactive or functionally altered

Direct action


The effects produced by free radicals that are created by the interaction of radiation with water molecules
Essentially all effects of irradiation in living cells result from this action

Indirect action


Why do essentially all effects of irradiation in living cells result from indirect action?

Because the human body is composed of 80-85% water and less than 1% DNA


Ionization of water molecules
Production of free radicals, undesirable chemical reactions and biologic damage, and cell-damaging substances
Organic free radical formation
The final result of the interaction of radiation with water is the formation of an ion pair (H+ and OH–) and two free radicals (H* and OH*)



Molecule that maintains normal cell function that is believed to be present in every cell and is vital to the survival of the cell

Master/key molecule


What is the master/key molecule presumed to be?



4 examples of radiosensitive cells

Basal cells of the skin
Blood cells such as lymphocytes (white blood cells) and erythrocytes (red blood cells)
Intestinal crypt cells
Reproductive germ cells


3 examples of radioinsensitive cells

Brain cells
Muscle cells
Nerve cells


As LET increases, the ability of the radiation to cause biologic effects also generally ________ until it reaches a maximal value



The radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation
True for all types of cells in the human body
The most pronounced radiation effects occur in cells having the least maturity and specialization or differentiation, the greatest reproductive activity, and the longest mitotic phases

Law of Bergoiné and Tribondeau


Equal doses of ionizing radiation produce ________ degrees of damage in different kinds of human cells because of differences in cell radiosensitivity



The more mature and specialized in performing functions a cell is, the ________ sensitive it is to radiation



A whole-body dose of what delivered within a few days produces a measurable hematologic depression?

0.25 Gyt


Precursors of red blood cells are among the most sensitive of human tissues; mature red blood cells are much less radiosensitive



Signifies the whole body dose of radiation that can be lethal to 50% of the exposed population within 30 days
Quantitative measurement that is fairly precise when applied to experimental animals
LD 50 for humans may require more than 30 days for its full expression

LD 50/30


What is the lethal dose of human beings usually given as and why?

LD 50/60 because a human's recovery is slower than that of laboratory animals, and death may still occur at a later time following a substantial whole-body exposure


What is the estimated lethal whole-body dose for humans?

3.0-4.0 Gyt


What is the most radiosensitive blood cells in the human body?



At the dose level of what does complete blood cell recovery occur shortly after irradiation?

0.25 Gyt or less


When a higher dose range of whole body radiation of what is received, the lymphocyte count decreases to zero within a few days (full recovery generally requires a period of several months after this level of exposure)?

0.5-1 Gyt


Scavenger type of white blood cells that fight bacteria; if they're affected by radiation, they can't fight bacteria



Initiate blood clotting and prevent hemorrhage
If affected by radiation, your blood won't clot so you won't stop bleeding if you cut yourself



Biologic effects of radiation that occur relatively soon after humans receive high doses of ionizing radiation
Substantial evidence of the consequences of such effects comes from numerous laboratory animal studies and data from observation of some irradiated human populations
Not common in diagnostic imaging
Produced by a substantial dose of ionizing radiation

Early effects


Ionizing radiation produces the greatest amount of biologic damage in the human body when a large dose of densely ionizing (_______-LET) radiation is delivered to a large or radiosensitive area of the body



Biologic damage sustained by living organisms (such as humans) as a consequence of exposure to ionizing radiation

Somatic effects


2 classifications of somatic effects depending upon the length of time from the moment of irradiation to the first appearance of symptoms of radiation damage

Early somatic effects
Late somatic effects


Effects are directly related to the dose received; as the radiation dose increases, the severity of these effects also increases.
These results have a threshold, a point at which they begin to appear and below which they are absent
The amount of biologic damage depends on the actual absorbed dose of ionizing radiation
Consequences include cell killing

Deterministic somatic effects (formerly called nonstochastic somatic effects)


2 categories of late effects (both of these types of late radiation-induced changes are consequences of high-level radiation exposure or of low doses of radiation delivered over a long interval of time)

Late deterministic somatic effects
Late stochastic (probabilistic) effects


Depend on the time of exposure to ionizing radiation
Requires a substantial dose of ionizing radiation to produce these biologic changes soon after irradiation
With the exception of certain lengthy high-dose-rate procedures, diagnostic imaging examinations do not usually impose radiation doses sufficient to cause early deterministic effects
High-dose effects include nausea, fatigue, erythema, epilation, blood disorders, intestinal disorders, fever, dry and moist desquamation, depressed sperm count in the male, temporary or permanent sterility in the male and female, and injury to the central nervous system (at extremely high radiation doses)

Early deterministic somatic effects


A whole-body dose of what can result in many of the manifestations or organic damage occurring in succession (acute radiation syndrome- early deterministic somatic effects)?

6 Gyt


Radiation sickness occurring in humans after whole-body reception of large doses of ionizing radiation delivered over a short period of time
A collection of symptoms associated with high-level radiation exposure

Acute radiation syndrome (ARS)


3 separate dose-related syndromes occur as part of the total-body syndrome (ARS)

Hematopoietic syndrome (bone marrow syndrome) Gastrointestinal syndrome
Cerebrovascular syndrome


Hematopoietic syndrome (bone marrow syndrome) occurs when people receive whole-body doses of ionizing radiation in what range that decreases the number of bone marrow stem cells?

1-10 Gyt


Radiation exposure causes the number of red blood cells, white blood cells, and platelets in the circulating blood to decrease
When the cells of the lymphatic system are damaged, the body loses some of its ability to combat infection
Because additional bone marrow cells are destroyed, as the radiation dose escalates, the body becomes more susceptible to infections (mostly from its own intestinal bacteria) and more prone to hemorrhage; when death occurs, it’s a consequence of bone marrow destruction

Hematopoietic syndrome (bone marrow syndrome)


Death may occur 6-8 weeks after irradiation in some sensitive human subjects who receive a whole-body dose exceeding what (hematopoietic syndrome [bone marrow syndrome])?

2 Gyt


Gastrointestinal syndrome appears at a threshold dose of approximately what and peaks after a dose of what?

6 Gyt, 10 Gyt


Without medical support to sustain life, exposed persons receiving doses of what may die 3-10 days after being exposed (gastrointestinal syndrome)?

6-10 Gyt


Survival time doesn’t change with dose
A few hours after the dose severe nausea, vomiting, and diarrhea persist for as long as 24 hours followed by a latent period as long as 5 days (during this time, the symptoms disappear); the manifest illness stage follows the period of false calm and the human subject experiences: severe nausea, vomiting, diarrhea and other signs and symptoms that may occur include: fever (as in hematopoietic syndrome), fatigue, loss of appetite, lethargy, anemia, leukopenia (decrease in the number of white blood cells), hemorrhage (GI tract bleeding occurs because the body loses its blood-clotting ability), infection, electrolyte imbalance, emaciation
Examples of humans who died as a result: workers and firefighters at Chernobyl

Gastrointestinal syndrome


What is the most radiosensitive part of the GI tract and why?

Small intestine because there’s a lot of absorption and cell regeneration


Cerebrovascular syndrome results when the central nervous system cardiovascular system receive doses of what (a dose of this magnitude can cause death a few hours to 2-3 days after exposure after exposure)?

50 Gyt


Eight signs and symptoms: excessive nervousness, confusion, severe nausea, vomiting, diarrhea, loss of vision, burning sensation of the skin, loss of consciousness
A latent period lasting up to 12 hours follows and during this time, symptoms lessen or disappear
After the latent period, the manifest illness stage occurs and during this period, the prodromal syndrome recurs with increased severity, and other symptoms appear, including: disorientation and shock, periods of agitation alternation with stupor, ataxia (confusion and lack of muscular coordination), edema in the cranial vault, loss of equilibrium, fatigue, lethargy, convulsive seizures, electrolytic imbalance, meningitis, prostration, respiratory distress, vasculitis, coma
Damaged blood vessels and permeable capillaries permit fluid to leak into the brain and cause an increase in fluid content
Final result of this damage is failure of the CNS and cardiovascular systems, which causes death withinn a matter of minutes
Because the GI and hematopoietic systems are more radiosensitive than the CNS, they’re also severely damaged and fail to function after a dose of this magnitude (hematopoietic and GI syndrome also going on)

Cerebrovascular syndrome


4 major response stages of ARS

Prodromal, or initial, stage
Latent period
Manifest illness
Recovery or death


Stage of ARS that occurs within hours after a whole-body absorbed dose of 1 Gyt or more
Characterized by nausea and vomiting
Severity of these symptoms is dose related: the higher the dose, the more severe the symptoms

Prodromal, or initial, stage


Stage of ARS about 1 week during which no visible symptoms occur

Latent period


Stage toward the end of the 1st week of ARS
The period when signs and symptoms that affect the hematopoietic, GI, and cerebrovascular systems become visible

Manifest illness


In severe high-dose cases, emaciated human beings eventually die
If, after a whole-body sublethal dose such as 2-3 Gyt, exposed persons pass thru the first three stages of ARS but show less severe symptoms than those seen after superlethal doses of 6-10 Gyt, this may occur in about 3 months

Recovery or death


Whole-body doses greater than what may cause the death of the entire pop in 30 days without medical support?

6 Gyt


In the repair of sublethal damage, oxygenated cells, which receive more nutrients, have a _______ prospect for recovery than do hypoxic cells that consequently receive fewer nutrients



Shrinkage of organs and tissues



Shedding of the outer layer of the skin (dry or moist/oozing) occurs at higher radiation doses (historical evidence)



Moderate doses of radiation may result in temporary hair loss
Large doses of radiation may result in permanent hair loss

Epilation or loss of hair (alopecia)


3 effects of ionizing radiation on the skin

Epilation or loss of hair (alopecia)


Doses as low as what can depress the male sperm population and has the potential to cause genetic mutations in future gens; in girls and women, a gonadal dose of what may delay or suppress menstruation?

0.1 Gyt


Temporary sterility may occur and last for as long as 12 months when the testes receive a radiation dose of what?

2 Gyt


Permanent sterility of the testes is most likely to be induced by a radiation dose of what?

5 or 6 Gyt


A single radiation exposure of what to the ovaries usually results in temporary sterility of the woman, whereas a dose of what results in permanent sterility?

2 Gyt
5-6 Gyt


Whole-body dose of ionizing radiation as low as what produce a measurable hematologic depression?

0.25 Gyt


Study of cell genetics with emphasis on cell chromosomes



A cytogenetic analysis of chromosomes may be accomplished through the use of a chromosome map consisting of a photomicrograph



The phase of cell division in which chromosome damage caused by radiation exposure can be evaluated
Chromosome aberrations (deviation from normal development or growth) and chromatid aberrations have been observed at this phase



Radiation-induced damage at the cellular level may lead to measurable somatic and genetic damage in the living organism as a whole later in life; these outcomes are the long-term results of radiation exposure

Late effects


3 examples of measurable late biologic damage

Genetic mutations


Radiobiologists engaged in research have a common goal to establish relationships between radiation and dose-response
Information obtained can be used to attempt to predict the risk of occurrence of malignancies in human populations that have been exposed to low levels of ionizing radiation
Radiation dose-response relationship is demonstrated graphically through a curve that maps the observed effects of radiation exposure in relation to the dose of radiation received
As radiation dose escalates, so do most effects
How much radiation received to give you this response

Dose-response curves


Straight line



Curved to some degree



A point at which a response or reaction to an increasing stimulation first occurs
With reference to ionizing radiation, below a certain radiation level or dose, no biologic effects are observed
Biologic effects begin to occur only when this level or dose is reached



Any radiation dose has the capability of producing a biologic effect
If ionizing radiation functions as the stimulus, and the biologic effect it produces is the response, and if a this relationship exists between radiation dose and a biologic response, some biologic effects will be caused in living organisms by even the smallest dose of ionizing radiation
No radiation dose can be considered absolutely safe



The equation that best fits the data has components that depend on dose to the first power (linear or straightline behavior) and also dose squared (quadratic/curved behavior)



The chance of a biologic response to ionizing radiation is directly proportional to the dose received
Recommends curve of radiation dose-response for most types of cancer

Linear nonthreshold (LNT) curve


Deterministic effects of significant radiation exposure such as skin erythema and hematologic depression may be demonstrated graphically
Biologic response does not occur below a specific dose level
Laboratory experiments on animals and data from human populations observed after acute high doses of radiation provided the foundation for this curve

Linear threshold dose-response curve


When living organisms that have been exposed to radiation sustain biologic damage

Somatic (i.e., body) effects


2 classifications of somatic effects

Stochastic effects
Deterministic effects


The probability that the effect happens depends upon the received dose, but the severity of the effect does not
Example: occurrence of cancer

Stochastic effects


Both the probability and the severity of the effect depend upon the dose
Example: a cataract

Deterministic effects


8 teratogenic effects

Embryonic, fetal, or neonatal death
Congenital malformations
Decreased birth weight
Disturbances in growth and/or development
Increased stillbirths
Infant mortality
Childhood malignancy
Childhood mortality


2 late stochastic effects

Genetic (heritable) effects


Consequences of radiation exposure that appear months or years after such exposure

Late somatic effects


Late effects that can be directly related to the dose received; slow developing changes to the body from radiation exposure
Not likely to occur from diagnostic imaging procedures

Late deterministic somatic effects


Late responses in the body to radiation exposure that do not have a threshold occur in an arbitrary or probabilistic manner and have a severity that does not depend on dose
Could be initiated by even the smallest amount of radiation exposure if many low probability occurrences were to be simultaneously realized.

Late stochastic effects


No conclusive proof exists that low-level ionizing radiation exposure below what causes a significant increase in the risk of malignancy?

0.1 Sievert (Sv)


3 major types of late effects

Carcinogenesis (stochastic event)
Cataractogenesis (deterministic event)
Embryologic effects (birth defects) (stochastic events)


2 models used by researchers for extrapolation of risk from high-dose to low-dose data

Linear-quadratic (leukemia only)


Most important late stochastic effect caused by exposure to ionizing radiation
This effect is a random occurrence that does not seem to have a threshold and for which the severity of the disease is not dose-related



There is a high probability that a single dose of approximately what will induce the formation of cataracts?

2 Gy


Radiation-induced cataracts in humans follow a what kind of relationship?

Threshold, nonlinear dose-response


Most radiosensitive stage of gestation in humans

First trimester


Set of numeric dose limits that are based on calculations of the various risks of cancer and genetic (hereditary) effects to tissues or organs exposed to radiation

Effective dose (EfD) limiting system


4 major organizations responsible for evaluating the relationship between radiation EqD and induced biologic effects and are also concerned with formulating risk estimates of somatic and genetic effects of irradiation

International Commission on Radiological Protection (ICRP)
National Council on Radiation Protection and Measurements (NCRP)
United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
National Academy of Sciences/National Research Council Committee on the Biological Effects of Ionizing Radiation (NAS/NRC-BEIR)


Evaluates information on biologic effects of radiation and provides radiation protection guidance through general recommendations on occupational and public dose limits
Considered the international authority on the safe use of sources of ionizing radiation
Composed of a main commission with 12 active members, a chairman, and 4 standing committees, which include committees on radiation effects, radiation exposure, protection in medicine, and the application of its recommendations
Since its inception in 1928, it has been the leading international organization responsible for providing clear and consistent radiation protection guidance through its recommendation for occupational dose limits and public dose limits
Only makes recommendations, does not function as an enforcement agency; each nation must develop and enforce its own specific regulations

International Commission on Radiological Protection (ICRP)


Reviews regulations formulated by the ICRP and decides ways to include those recommendations in US radiation protection criteria; nongovernmental, non-profit
The council implements this task by formulating general recommendations and publishing their recommendations in the form of various reports
Not an enforcement agency, enactment of its recommendations lies with federal and state agencies that have the power to enforce such standards after they have been established

National Council on Radiation Protection and Measurements (NCRP)


Evaluates human and environmental ionizing radiation exposure and derives radiation risk assessments from epidemiologic data and research conclusions; provides information to organizations such as the ICRP for evaluation
Another group that plays a prominent role in the formulation of radiation protection guidelines
This group evaluates human and environmental ionizing radiation exposures from a variety of sources including radioactive materials, radiation-producing machines, and radiation accidents
Uses epidemiologic data information acquired from the Radiation Effects Research Foundation and research conclusions to derive radiation risk assessments for radiation-induced cancer and for genetic (hereditary) effects

United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)


Reviews studies of biologic effects of ionizing radiation and risk assessment and provides the information to organizations such as the ICRP for evaluation
Another advisory group that reviews studies of biologic effects of ionizing radiation and risk assessment

National Academy of Sciences/National Research Council Committee on the Biological Effects of Ionizing Radiation (NAS/NRC-BEIR)


5 U.S. regulatory agencies

Nuclear Regulatory Commission (NRC)
Agreement states
Environmental Protection Agency (EPA)
U.S. Food and Drug Administration (FDA)
Occupation Safety and Health Administration (OSHA)


Oversees the nuclear energy industry and enforces radiation protection standards, publishes its rules and regulations in Title 10 of the U.S. Code of Federal Regulations, and enters into written agreements with state governments that permit the state to license and regulate the use of radioisotopes and certain other material within the state
Federal agency that has the authority to control the possession, use, and production of atomic energy in the interest of national security; also has the power to enforce radiation protection standards
Does not regulate or inspect x-ray imaging facilities; its main function is to oversee the nuclear energy industry
Supervises the design and working mechanics of nuclear power stations, production of nuclear fuel, handling of expending fuel, and supervision of hazardous radioactive waste material
Controls the manufacture and use of radioactive substances formed in nuclear reactors and used in research, nuclear medicine imaging procedures, therapeutic treatment, and industry
Licenses users of radioactive materials and periodically makes unannounced inspections to determine whether these users are in compliance with the provisions of their licenses
Writes standards that are presented as rules and regulations
Has the authority to enter into written contracts with state governments; these agreements permit the contracting state to undertake the responsibility of licensing and regulating the use of radioisotopes and certain other radioactive materials within the state

Nuclear Regulatory Commission (NRC)


Enforce radiation protection regulations through their respective health departments

Agreement states


Facilitates the development and enforcement of regulations pertaining to the control of radiation in the environment

Environmental Protection Agency (EPA)


Conducts an ongoing production radiation control program, regulating the design and manufacture of electronic products, including x-ray equipment
To determine the level of compliance with standards in a given x-ray facility, it conducts on-site inspections of x-ray equipment
Compliance with standards ensures the protection of occupationally and nonoccupationally exposed persons from faulty manufacturing

U.S. Food and Drug Administration (FDA)


Functions as monitoring agency in places of employment, predominantly in industry
Regulates occupation exposure to radiation

Occupation Safety and Health Administration (OSHA)


2 functions of an RSO

Oversee the program’s daily operation
Provide for formal review of the program each year


5 responsibilities of the RSO

Specifically responsible for developing an appropriate radiation safety program for the facility that follows internationally accepted guidelines for radiation protection
Must ensure that the facility’s operational radiation practices are such that all people, especially those who are or could be pregnant, are adequately protected from unnecessary exposure
To fulfill their responsibility, management of the facility must grant the RSO the authority necessary to implement and enforce the policies of the radiation safety program
Review and maintain radiation-monitoring records for all personnel
Be available to provide counseling for individuals


Consistency in output in radiation intensity for identical generator settings from one individual exposure to the next
The x-ray unit must be able to duplicate certain radiographic exposures for any given combo of kilovolts at peak (kVp), milliamperes (mA), and time
May be verified by using the same technical exposure factors to make a series of repeated radiation exposures and then, observing with a calibrated ion chamber, how radiation intensity typically varies

Exposure reproducibility


A variance of what is acceptable for exposure reproducibility?

5% or less


Consistency in output radiation intensity at a selected kVp setting when changing from one mA and time combination to another (mAs); output of radiation that comes out
The ratio of the difference in mR/mAs values between two successive generator stations to the sum of those mR/mAs values

Exposure linearity


What must exposure linearity be?

Less than 0.1 (cannot exceed 10%)


What is the model for the ALARA concept?

The relationship between ionizing radiation and potential risk is assumed to be completely linear and without any threshold
In the interest of safety, risk of injury should be overestimated rather than underestimated


Biologic effect and radiation dose are directly proportional



2 all-inclusive categories encompass the radiation-induced responses of serious concern in radiation protection programs

Deterministic effects
Stochastic (probabilistic) effects


Biologic somatic effects of ionizing radiation that can be directly related to the dose received that exhibit a threshold dose below which the response does not normally occur and above which the severity of the biologic damage increases as the dose increases
When radiation-induced biologic damage escalates, it does so because greater numbers of cells interact with the increased number of x-ray photons that are present at higher radiation exposure
Typically occur only after large doses of radiation but they could also result from long-term individual low doses of radiation sustained over several years; in either instance the cumulative amounts of such radiation doses are usually much greater than those typically encountered by a patient in diagnostic radiology

Deterministic effects


3 early deterministic effects

Blood changes (decrease pf lymphocytes and platelets)
Acute radiation syndrome


3 syndromes of acute radiation syndrome (far more serious early deterministic consequences of radiation sickness)

Hematopoietic syndrome
Gastrointestinal syndrome
Cerebrovascular syndrome


6 late deterministic somatic effects that may occur months or years after high-level radiation exposure

Cataract formation
Organ atrophy
Loss of parenchymal cells
Reduced fertility
Sterility caused by a decrease in reproductive cells


The frequency of occurrence of high-dose deterministic effects follows what curve?

Nonlinear, threshold curve that is sigmoidal (S-shaped) with a threshold
Not proportional to the dose


Mutational, nonthreshold, randomly occurring biologic somatic changes; chances of occurrence increase with each radiation exposure

Stochastic (probabilistic) effects


2 examples of stochastic (probabilistic) effects

Genetic alterations


What curves may be used to demonstrate stochastic (probabilistic) effects?

Linear and the linear-quadratic dose-response curves


Current radiation protection philosophy is based on the assumption that what relationship exists between radiation dose and biologic response?

Linear nonthreshold relationship


Current method for assessing radiation exposure and associated risk of biologic damage to radiation workers and the general public
Concerns the upper boundary dose of ionizing radiation that results in a negligible risk of bodily injury or hereditary damage
Upper boundary limits are designed to minimize the risk to humans in terms of deterministic and stochastic effects (upper limits do not include natural background and medical exposure)
Upper boundary radiation exposure limits for occupationally exposed persons are associated with risks that are similar to those encountered by employees in other industries such as manufacturing, trade, or government, which are generally considered to be reasonably safe
Radiation risks are derived from the complete injury caused by radiation exposure
Includes, for the determination of EqD for tissues and organs, all radiation-vulnerable human organs that can contribute to potential risk, rather than only those human organs considered critical
An attempt to equate the various risks of cancer and hereditary effects to the tissues or organs that were exposed to radiation

EfD limiting system


3 ways EfD limits may be expressed

Whole-body exposure
Partial-body exposure
Exposure of individual organs


The sum of what exposures is considered when EfD limits are established?

Both the external and internal whole-body exposures


Embryo-fetus in utero is particularly sensitive to radiation exposure; epidemiologic studies of atomic bomb survivors exposed in utero provided conclusive evidence of a dose-dependent increase in the incidence of severe mental retardation for fetal doses greater than approximately what?

0.4 Sievert (Sv)


What is the annual EfD limit for occupational exposure?

50 mSv


What is the cumulative EfD (cumEfD) limit for occupational exposure?

10 mSv x age


What is the annual EqD limit for occupational exposure to the lens of the eye?

150 mSv


What is the annual EqD limit for occupational exposure to localized areas of the skin, hands, and feet?

500 mSv


What is the annual EfD limit for continuous or frequent exposure to the public (ex: radiation therapy)?

1 mSv


What is the annual EfD limit for infrequent exposure to the public?

5 mSv


What is the annual EqD limits for the public to the lens of the eye?

15 mSv


What is the annual EqD limits for the public to localized areas of the skin, hands, and feet?

50 mSv


What is the annual EfD limit for education and training exposures (students) under the age of 18 years?

1 mSv


What is the annual EqD limit for education and training exposures (students) to the lens of the eye?

15 mSv


What is the annual EqD limit for education and training exposures (students) to localized areas of the skin, hands, and feet?

50 mSv


What is the monthly EqD limit for embryo and fetus exposures?

0.5 mSv


What is the EqD limit for embryo and fetus exposures during the entire gestation?

5.0 mSv


What is the annual negligible individual dose?

0.01 mSv


A radiation worker's lifetime EfD must be limited to his or her age in years times 10 mSv

Cumulative effective dose (CumEfD) limit


2 exposures EfD limits include the possibility of

Internal exposure
External exposure


The sum/total of both the internal and external equivalent doses

Effective dose (EfD)


Provides a low-exposure cutoff level so that regulatory agencies may dismiss a level of individual risk as being of negligible risk

Negligible individual dose (NID)


X-rays produced in the anode but not at the focal spot
Photons that pass through the housing because the lead shielding around the tube for practical reasons cannot be made perfect
Radiation generated in the x-ray tube that does not exit from the collimator opening but rather penetrates the protective tube housing and, to some degree, the sides of the collimator

Off-focus/leakage radiation


X-rays emitted through the x-ray port tube window, or port

Useful, or primary, beam


The housing enclosing the x-ray tube must be constructed so that the leakage radiation measured at a distance of 1 m from the x-ray source does not exceed what when the tube is operated at its highest voltage at the highest current that allows continuous operation?

1 mGya/hr (100 mR/hr)


What is the radiographic examination table frequently made of?

Carbon fiber material


Distance indicators must be accurate to within what percent of the SID?



Centering indicators must be accurate to within what percent of the SID?



Most versatile device for defining the size and shape of the radiographic beam; most often used with multipurpose x-ray units
Box shaped and contains the radiographic beam defining system

Light-localizing variable-aperture rectangular collimator


3 things that radiographic beam defining system consists of

Two sets of adjustable lead shutters mounted within the device at different levels
A light source to illuminate the x-ray field and permit it to be centered over the area of clinical interest
Mirror to deflect the light beam toward the patient to be radiographed


Mounted as close as possible to the tube window to reduce the amount of off-focus, or stem, radiation coming from the primary beam exiting at various angles from the x-ray tube window; reduces patient dose resulting from off-focus radiation

Upper shutters (first set of shutters)


4 x-ray beam limitation devices

Light-localizing variable-aperture rectangular collimator
Aperture diaphragms


2 things x-ray beam limitation devices do

Confine the useful, or primary, beam before it enters the area of clinical interest, thereby limiting the quantity of body tissue irradiated
Reduces the amount of scattered radiation in the tissue and prevents unnecessary exposure to tissues not under examination


All the radiation that arises from the interaction of an x-ray beam with the atoms of a patient or any other object in the path of the beam
Compton interaction between the x-ray photons and electrons of the atoms within the attenuating object deflect x-ray photons from their initial trajectories; as a result, photons emerge from the object in all directions
Greatly reduced in intensity relative to the incident beam; also quite weakened in energy and consequently in penetrability

Scatter radiation


2 benefits of restricting x-ray field size to include only the anatomic structures of clinical interest

Significant reduction in patient dose because less scatter radiation is produced by a smaller field size
Improves the overall quality of the radiographic image


Mounted below the level of the light source and mirror and function to further confine the radiographic beam to the area of clinical interest
Consists of two pairs of lead plates oriented at right angles to each other; each set may be adjusted independently so that an extensive variety of rectangular shapes can be selected

Lower shutters (second set of shutters)


The brightness of a surface; quantifies the intensity of a light source (i.e., the amount of light per unit area coming from its surface)
Determined for measuring the concentration of light over a particular field of view
Light emission



The sum of the cross-table and along-the-table alignment differences between the x-ray and light beams must not exceed what of the SID?



Consists of electronic sensors in an IR holder that sends signals to the collimator housing; when activated, the collimators are automatically adjusted so that the radiation field matches the size of the IR
May be activated with the turn of a key

Positive beam limitation (PBL)


Regulatory standards require accuracy of what of the SID with PBL?



Simplest of all beam limitation devices
Consists of a flat piece of lead with a hole of designated size and shape cut in its center; the dimensions of the hole determine the size and shape of the radiographic beam
Different IR sizes and SIDs require aperture diaphragms of various sizes to accommodate them
Placed directly below the window of the x-ray tube and confines the primary radiographic beam to dimensions suitable for covering a given size IR at a specified SID
Limits field size, and thus the area of the body irradiated,

Aperture diaphragms


3 shapes of aperture diaphragm openings



Most common shape of aperture diaphragm



Circular metal tubes that attach to the x-ray tube housing or variable rectangular collimator to limit the x-ray beam to a predetermined size and shape



Collimating device with the diameter of the upper end smaller than the diameter of the lower end

Flared metal tube


Collimating device with the diameter the same at both the upper and lower ends

Straight cylinder


Reduces exposure to the patient's skin and superficial tissue by absorbing most of the lower-energy photons (long-wavelength or soft x-rays) from the heterogenous beam
Increases the mean energy, or "quality," of the x-ray beam aka "hardening" the beam; x-rays are more penetrating



What is the effect of filtration on the absorbed dose to the patient?

Because filtration absorbs some of the photons in a radiographic beam, it decreases the overall intensity (quantity, or amount) of incident radiation
The remaining photons, as a whole, are more penetrating and therefore less likely to be absorbed in body tissue
Hence, the absorbed dose to the patient decreases when the correct amount and type of filtration are placed in the radiographic beam


2 types of filtration



Filtration in the tube

Inherent filtration


3 examples of inherent filtration

Glass envelope encasing the x-ray tube
Insulating oil surrounding the tube
Glass window in the tube housing


The inherent filtration material amounts to approximately what aluminum equivalent?

0.5 mm aluminum equivalent


The light-localizing variable-aperture rectangular collimator provides an additional what amount of aluminum equivalent to the inherent filtration (the reflective surface of the collimator mirror provides most of this aluminum equivalent)?

1 mm aluminum equivalent


What is the requirement for total filtration?

2.5 mm aluminum equivalent at above 70 kVp


Inherent filtration plus added filtration

Total filtration


3 examples of added filtration

Sheets of aluminum (or the equivalent) of appropriate thickness


Extra filtration located outside the glass envelope window of the tube housing above the collimator shutters
Filtration below the tube

Added filtration


Each x-ray tube and collimator system typically has a total inherent filtration of what aluminum equivalent?

1.5 mm equivalent


Metal the is the most wide selected filter material in diagnostic radiology because it effectively removes low-energy (soft) x--rays from polyenergetic (heterogenous) x-ray beam without severely decreasing the x-ray beam intensity
Lightweight, sturdy, relatively inexpensive, and readily available

Aluminum (Z=13)


The thickness of a designated absorber (customarily a metal such as aluminum) required to decrease the intensity of the primary beam by 50% of its initial value
Measure of beam quality/effective energy of the x-ray beam

Half-value layer (HVL)


Dose reduction and uniform radiographic imaging of body parts that vary considerably in thickness or tissue composition may be accomplished by the use of these filters
Partially attenuate x-rays that are directed toward the thinner, or less dense, area while permitting more x-radiation to strike the thicker, or denser area

Compensating filters


3 materials compensating filters are constructed of

Other suitable material


3 types of compensating filters

Wedge filter
Trough, or bilateral wedge filter


Used to provide uniform density when the foot is undergoing radiography
Filter is attached to the lower rim of the collimator and positioned with its thickest part toward the toes and thinnest part toward the heel

Wedge filter


3 examinations a trough, or bilateral wedge filter is used in

Lateral knee (patella)
Dedicated chest radiographs


3 materials that may make up the grid interspaces



Device made of parallel radiopaque strips alternately separated with low-attenuation strips; strips of lead with aluminum between them
Placed between the patient and radiographic IR to remove scattered x-ray photons that emerge from the patient before they reach the film or other IR
Increases patient dose, but improves quality of the recorded image
Remove scattered x-ray photons

Radiographic grid


When is a grid usually used?

When the thickness of the body part to be radiographed is greater than 10 cm


The ratio of the height of the lead strips in the grid to the distance between them

Grid ratio


2 types of grids

Focused grid
Parallel grid


Grid whose lines follow divergence of beam, slanted in and meet at anode; used in diagnostic

Focused grid


Has straight grid lines

Parallel grid


2 things grids significantly improve

Radiographic contrast
Visibility of detail


What is the minimum SSD for mobile radiographic units?

At least 30 cm (12 inches)


What distance is generally used for mobile radiography?

100 cm (40 inches) or even 120 cm (48 inches)


Temporary image produced conventionally by ionizing radiation after x-rays pass through an anatomic area of clinical interest

Invisible/latent image


Invisible/latent image must be chemically processed to make the unseen image visible; the finished radiograph that results from this process

Analog image


Anatomic information collected by a computer and shown on its display

Digital image


Shades of gray that are displayed on the image



Number of different shades of gray that can be stored in memory and displayed on a computer monitor



The numeric values of the digital image are aligned in a fixed number of arrays that form many individual miniature square boxes, each of which corresponds to a particular place in the image; these individual boxes collectively constitute this

Image matrix


Each miniature square box in a matrix that collectively produce a 2D representation of the information contained in a volume of tissue

Picture element/pixel


What do the size of the pixels determine?

The sharpness of the image


Resolution is sharper when pixels are _______ and matrix is ________

Smaller, bigger


What is an advantage and disadvantage of DR?

Advantage: contrast better because image can be manipulated
Disadvantage: film offers better detail


IRs used in DR convert the energy of x-rays into what?

Electrical signals


What does indirect DR use?

A scintillator, such as amorphous silicon, to convert the x-ray energy into visible light
The visible light is converted into electrical signals by an array of transistors (TFTs) or an array of charge-coupled devices (CCDs)


What does direct DR use?

A photoconductor, such as amorphous selenium, to convert the x-ray energy directly into electrical signals


The CR filmless cassette contains a photostimulable phosphor made of what?

Europium-activated barium fluorohalide


Use of an image reading unit to scan the photostimulable phosphor image plate in CR uses what kind of beam?

Helium-neon laser beam


Use of an image reading unit to scan the photostimulable phosphor image plate in CR, results in the emission of violet light that is changed into an electronic signal by what?

A photomultiplier tube


Although the radiographer can manipulate the CR image of the patient's anatomy of interest to adjust image size, brightness, and contrast, this technologic flexibility does not excuse overexposing the patient
Responsibility of the radiographer to minimize radiation exposure by using correct technical exposure factors the first time a patient is x-rayed
If patients are overexposed by radiographers who claim the rationale that computerized images can be manipulated later on to produce a diagnostic-quality image, thereby avoiding the possibility of repeat exposures, patients are actually receiving higher radiation doses than are necessary to produce those initial images

Dose creep


CR has ________ kilovoltage flexibility than does conventional screen-film radiography



CR is _______ sensitive to scatter radiation, so a grid should probably be used more frequently except for the majority of pediatric patients

More (most)


How long does the image stay on the CR imaging plate?

8 hours


4 advantages DR systems offer advantages over both CR and conventional SFSs

Lower dose
Ease of use
Immediate imaging results
Manipulation of the image


Traditionally, fluoroscopic imaging systems have the x-ray tube positioned _____ the x-ray examination table and the image intensifier and spot film system mounted on a C-arm and centered over the x-ray examination table



Minification gain x flux gain

Brightness gain


3 benefits of image intensification fluoroscopy

Increased image brightness
Saving of time for for the radiologist
Patient skin dose reduction (scatter goes back to floor)


The x-ray image intensification system increases the overall brightness of fluoroscopic image how many times?

10,000 times


Daytime vision

Photopic/cone vision


Night vision

Scotopic/rod vision


Because an image intensification system permits observing of the fluoroscopic image at ordinary brightness levels (regular white light) that radiologist makes use of what type of vision?

Daytime vision
Photopic/cone vision


What is the input phosphor of a fluoroscopic image intensification system made of?

Cesium iodide


What is the photocathode of a fluoroscopic image intensification system made of?

Photoemissive materials


What is the output phosphor of a fluoroscopic image intensification system made of?

Zinc cadmium


An electronic device that receives the image-forming x-ray beam and converts it into a visible-light image of high intensity

Image intensification tube


When magnification in the fluoroscopic image is needed and the viewing mode is changed to the 17-cm mode (6.8 in) or even less (12 cm [4.8 cm]), the focal point of the electrons move to a _________ from the output phosphor

Greater distance away


Fluoroscopy mA _________ automatically with magnification; the use of smaller-diameter modes results in increased pt dose
Quality of the magnified image is somewhat _________ (new digital systems can magnify without increasing dose)

Increases, degraded


Involves manual or automatic periodic activation of the fluoroscopic tube by the fluoroscopist, rather than lengthy continuous activation

Intermittent, or pulsed, fluoroscopy


2 things intermittent/pulsed fluoroscopy does

Practice significantly decreases patient dose, especially in long procedures
Helps extend the life of the tube


Feature that allows the fluoroscopist to see the most recent image without exposing the patient to another pulse of radiation; reduces patient dose



What is the kVp range for adults, depending on the body area being examined during fluoroscopy; mA range varies

75-110 kVp


The SSD should not be less than what for stationary fluoroscopes?

38 cm (15 inches)


Position of the input phosphor surface of the image intensifier in relation to the patient should be maintained as ________ as is practical to reduce the patient’s entrance exposure rate



What is the minimum SSD for mobile fluoroscopes?

No less than 30 cm (12 inches)


Resettable device that times the x-ray beam-on time and sounds an audible alarm or temporarily interrupts the exposure after the fluoroscope has been activated for 5 minutes

Cumulative timer


What is the current federal standard limit for entrance skin exposure rates of general-purpose intensified fluoroscopic units?

Maximum of 100 mGya per minute (10 R/min)


A primary protective barrier of what lead equivalent is required for a fluoroscopic unit?

2-mm lead equivalent


Patient-image intensifier distance should be as _______ as possible to reduce entrance dose (puts tube further)



With the C-arm x-ray tube positioned _______ the patient, scatter radiation is less intense



The lines composing the image are progressively scanned to provide the picture that appears on a monitor during a brief period of time
The x-ray beam is turned off while the image is being scanned, thereby decreasing patient dose, and then pulsed back on for the next image

Pulsed progressive system


Treating the patient as a whole person rather than just the area of concern

Holistic approach


An interaction that produces a satisfying result through an exchange of information

Effective communication


Unconscious actions or body language

Nonverbal communication


2 types of patient motion

Voluntary motion
Involuntary motion


Motion controlled by will

Voluntary motion


Motion caused by muscle groups (digestive organs or heart)

Involuntary motion


4 areas of the body that should be selectively shielded from the useful beam whenever possible

Lens of the eye
Reproductive organs


Gonadal shielding should be used on patients during diagnostic x-ray procedures to protect the reproductive organs from exposure to the useful beam when these organs are in or within approximately what distance of a properly collimated beam?

5 cm


Female reproductive organs receive about how many times more exposure during a given radiographic procedure involving the pelvic region than do the male reproductive organs, because the female reproductive organs are located within the pelvic region?

3 times


A 1-mm lead flat contact shield for the female reduces exposure by about what percent?



A 1-mm lead contact shield for the male patient reduces exposure by about what percent?



When a female patient is in the supine position the shield should be placed approximately how far medial to each palpable anterior superior iliac spine (ASIS) to protect the ovaries?

2.5 cm (1 inch)


4 basic types of gonadal shielding devices

Flat contact shields
Shadow shields
Shaped contact shields
Clear lead shields


Shield made of lead strips or lead-impregnated materials 1 mm thick
Can be placed directly over the patient's reproductive organs
Most effective when they're used as protective devices for patients having AP or PA while in a recumbent position; not suited for nonrecumbent positions or projections other than AP or PA

Flat contact shields


If the flat contact shield is used during a typical fluoroscopic examination, it must be placed _____ the patient to be effective because the x-ray tube is located under the radiographic table



Shield made of radiopaque material and is suspended from above the radiographic beam-defining system, these shields hang over the area of clinical interest to cast a shadow; sterile field

Shadow shields


Shields containing 1 mm of lead and are contoured to enclose the male reproductive organs
Disposable or washable athletic supporters or jockey-style briefs function as carriers for these shields
Not recommended for PA projections because it only covers the anterior and lateral surfaces

Shaped contact shields


Shields made of transparent lead-acrylic material impregnated with approximately 30% lead by weight
Ex: full spinal scoliosis examination

Clear lead shields


Recorded detail in the radiographic image

Spatial resolution


Blotchy radiographic image that results when an insufficient quantity of x-ray photons reaches the IR

Quantum noise/mottle


What is the voltage ripple of a single phase generator?



What is the voltage ripple of a 3 phase 6 pulse generator?



What is the voltage ripple of a 3 phase 12 pulse generator?



What is the voltage ripple of a high frequency generator?



Product of x-ray electron tube current and the amount of time in seconds that the x-ray beam is on

Milliampere-seconds (mAs)


As an alternative procedure instead of using a radiographic grid for reducing scattered radiation during certain examinations (e.g., cross-table lateral c-spine and areas of chest radiography)
Technique that removes scatter radiation by using an increased OID which improves radiographic image contrast
A complementary increase in SID may be made
The scattered x-rays are disseminated in many directions at acute angles to the primary beam when the radiographic exposure is made
Because of the increased distance between the anatomic structures being imaged and the IR, a higher percentage of the scattered x-rays produced is then less likely to strike the IR

Air-gap technique


In general, the use of an air gap technique requires the selection of technical exposure factors are comparable to those used with what ratio grid?

8:1 ratio grid


If the patient's gonads were included in the repeated imaged area, then the gonads would have received this

Double dose


6 unnecessary radiologic procedures

Chest x-ray examination on scheduled admission to the hospital
Chest x-ray as part of a preemployment physical
Lumbar spine examination as part of a preemployment physical
Chest x-ray or other unjustified examination as part of a routine health checkup
Chest x-ray examination for mass screening for tuberculosis (TB)
Whole-body multislice spiral computed tomography (CT) screening


Most frequently reported patient radiation amount because it is the simplest to determine

Entrance skin exposure (ESE)


Sensing devices most often used to measure skin dose directly

Thermoluminescent dosimeter (TLD)


Absorbed dose to the most superficial layers of the skin

Skin dose


The EqD to the reproductive organs that, if received by every human, would be expected to bring about an identical gross genetic injury to the total population, as does the sum of the actual doses received by exposed individual members of the population
The consequences of substantial absorbed doses of gonadal radiation become significantly less when averaged over an entire population rather than applied to just a few of its members
The average EqD to members of the population who are of childbearing age

Genetically significant dose


What is the estimated GSD for U.S. population?

0.20 mSv (20 mrem)


Most medical procedures result in fetal exposures of less than what?

Less than 0.01 Gy


Product of the average absorbed dose (D) in a tissue or organ in the human body and its associated radiation weighting factor chosen for the type and energy of the radiation in question for radiation workers

Equivalent dose (EqD)


4 imaging procedures that increase the radiographer's risk of exposure

General fluoroscopy (diagnostic)
Mobile examinations
C-arm fluoroscopy
General radiographic procedures


2 types of secondary radiation

Scatter radiation
Leakage radiation


What is the minimum thickness protective aprons can be during fluoroscopy?

0.5 mm of lead equivalent


Most effective means of protection from ionizing rdiation



The intensity of radiation is inversely proportional to the square of the distance from the source
Expresses the relationship between distance and intensity (quantity) of radiation and governs the dose received
As the separation between the radiation source and measurement point increases, the quantity of radiation measured at the more distant position decreases by the square of the ratio of the original new distance from the source; this decrease in radiation intensity physically occurs because the area, which the same flux of x-rays at the original location now covers at the new location, has increased by the square of the relative distance change
When the distance from a point source of radiation is doubled, the radiation at the new location spans an area four times larger than the original area; however, the intensity at the new distance is only one fourth the original intensity

Inverse square law (ISL)


What is the formula for the inverse square law?



2 most common materials used for structural protective barriers



4 accessory protective devices made of lead-impregnated vinyl (devices provide protection when not behind a stationary barrier)

Thyroid shields
Protective eyeglasses


3 factors the effectiveness of shielding material depends on

Atomic number


Prevent direct, or unscattered, radiation from reaching personnel or members of the general public on the other side of the barrier
Located perpendicular to the undeflected/primary line of travel of the x-ray beam
Ex: wall behind wall bucky

Primary protective barrier


2 specifications for a primary barrier at 130 kvp

Consists of 1.6 mm (1/16 inch) lead
Extends 2.1 m (7 feet) upward from the floor of the x-ray room when the x-ray tube is 1.5 to 2.1 m (5 to 7 feet) from the wall in question


Radiation that has been deflected from the primary beam
Made of leakage from the tube housing and scatter (primarily from the patient) radaition

Secondary radiation


Protects against secondary radiation (leakage and scatter radiation)
Any wall or barrier that is never struck by the primary x-ray beam (this does not mean that secondary radiation cannot hit primary barriers as well)
Walls that are not in the direct line of travel of the primary beam

Secondary protective barriers


2 specifications of secondary protective barriers

Should overlap the primary protective barrier by approximately 1.27 cm (1/2 inch)
Consists of 0.8 mm (1/32-inch) of lead


Protects the radiographer from secondary radiation (leakage and scatter)
Located in x-ray rooms housing permanent or nonportable radiographic equipment
To ensure maximal protection during radiographic exposures, personnel must remain completely behind the barrier
Exposure cord must be short enough that the exposure switch can be operated only when the radiographer is completely behind the control-booth barrier

Control-booth barrier


2 specifications of the control-booth barrier

Must extend 2.1 m (7 feet) upward from the floor
Must be permanently secured to the floor


Diagnostic x-rays should scatter a minimum of how many times before reaching any area behind the control-booth barrier?

Two times


The observation window in the control-booth barrier typically consists of what lead equivalent?

1.5-mm lead equivalent


With appropriate lead equivalent in the control-booth barrier, exposure of the radiographer will not exceed a maximum allowance of how much radiation per week; in actual practice in a well-designed facility, exposure should not exceed how much radiation per week?

1 mSv (100 mrem)
0.02 mSv (2 mrem)


Contains clear lead-acrylic material impregnated with approximately 30% lead by weight
Permits a panoramic view, allowing diagnostic imaging personnel to observe the patient more completely

Clear lead-acrylic secondary protective barrier


3 specifications of modular x-ray barriers

Shatter resistant
Can extend 2.1 m (7 feet) upward from the floor
Available in lead equivalency from 0.3 to 2 mm


Clear lead-acrylic overhead protective barriers can be used as overhead x-ray barrier to provide an open view during special procedures and cardiac catheterization; shielding typically offers what lead equivalency protection?

0.5-mm lead equivalency


For 100 kVp, an apron must be equivalent to at least what thickness of lead?



Protective gloves must have what lead equivalent?

0.25-mm lead equivalent


What is the minimum lead equivalent for thyroid neck shields?

0.5-mm lead equivalent


What is the minimal lead equivalent protective level for protective eyeglasses

0.35 mm


A spot film device protective curtain, or sliding panel, should have a minimum of what lead equivalent and should normally be positioned between the fluoroscopist and the patient to intercept scattered radiation above the tabletop?

0.25-mm lead equivalent


A bucky slot shielding device should have at least what lead equivalent and must automatically cover the bucky slot opening in the side of the x-ray table during a standard fluoroscopic examination when the bucky tray is positioned at the foot end of the table which protects radiologist and radiographer at gonadal level ?

0.25-mm lead equivalent


For mobile x-ray units that are non-remote-controlled, the cord leading to the exposure switch must be long enough to permit the radiographer to stand at least how far from the patient, the x-ray tube, and the useful beam (permits use of ISL)?

2 m (approximately 6 feet)


Radiographer should attempt to stand how to the x-ray beam–scattering object (the patient) line (when protection factors of distance and shielding have been accounted for, this is the place at which the least amount of scattered radiation is received)?

At a right angle (90-degrees)


During c-arm fluoroscopy, the exposure rate caused by scatter near the entrance surface of the patient (the x-ray tube side) ________ the exposure rate caused by scatter near the exit surface of the patient; the location of the _______ potential scatter dose is on the side of the patient away from the x-ray tube (i.e., the image intensifier side)

Exceeds; lower


In most facilities room doors have attenuation for diagnostic energy x-rays equivalent to that provided by how much lead?

0.8 mm (1/32 inch) of lead


3 categories of radiation sources generated in an x-ray room

Primary radiation
Scatter radiation
Leakage radiation


Emerges directly from the x-ray tube collimator and moves without deflection toward a wall, dorr, viewing window, and so on
Energy has not been degraded by scatter, and substantial portions of the initial beam may not have been attenuated

Primary radiation
Direct radiation


Some isotopes have too many neutrons or protons; because of this, such isotopes spontaneously undergo changes or transformations to rectify the understandable arrangement



Unstable and therefore radioactive isotope of the element iodine
Prostate tracers are permanently implanted for prostate radiation therapy

Iodine-125 (125I)


For a patient with thyroid cancer, it is desirable to strongly irradiate any residual thyroid tissue not removed by surgery using this isotope

Iodine-131 (131I)


How thick are rolling lead shields?

1 inch


What is the dose limit suggested by the EPA during an emergency situation for individuals engaged in nonlifesaving activities?

50 mSv per event


What is the dose limit suggested by the EPA during an emergency situation for individuals engaged in lifesaving activities?

250 mSv per event