Flashcards in Radiology I Deck (165):
Radiation is the transmission of energy through space and matter and occurs in what 2 forms?
Radioactivity releases alpha or beta particles or gamma rays generated where?
Inside the nucleus
Oral and maxilofacial radiology involves only what type of radiation?
What type of radiation in the electromagnetic spectrum is capable of ionizing matter?
High energy (UV and up)
Electromagnetic radiation is generated when the velocity of an electrically charged particle is altered
The energy of dental x-rays is 60k to 90 k.... (unit?)
The x-ray tube is surrounded by insulating material, usually what?
The X-ray tube has electrons stream from the ______ to target the ______.
*energy from some e- is converted into x-rays
The Filament (the source of electrons within an x-ray tube) is a coil of ______ wire.
The Focusing Cup is a negatively charged concave reflector of ________ surrounding the Filament.
The Anode is a ______ target embedded in copper
The sharpness of an x-ray image ________ as the size of the focal spot Decreases.
What type of Radiation primarily emanates from an x-ray tube?
*German for "braking radiation"
Bremsstrahlung Radiation generates x-ray photons with a continuous spectrum of energy and the beam is usually described by its peak operating voltage which is what?
*so, fluctuated up to 70
The exposure time of an x-ray takes how long?
*time is directly proportional to photon exposure
fractions of second
The number of photos that reach the patient and image receptor is directly proportional to what 2 things?
Beam quantity/intensity refers to what?
Number of photons in x-ray beam
What factor is related to the Tube Voltage Peak (kVp)?
Quality (meaning energy of x-ray beam)
Increasing the kVp of an x-ray increases what 3 things?
mean energy of those photons
maximal energy of photons
Low energy photons that can't reach the receptor still might do damage to the patient and these can be removed by a filter
There is inherent filtration the x-ray passes through like glass, oil, etc. as passes through the machine, but what kind of filter preferentially removes low Energy photons?
The Collimator is a metallic barrier used to restrict x-ray size and is Round or Rectangular
The Collimator improves the image quality by decreasing what?
Scattered Radiation produced by absorbed photons
Describe the Inverse Square Law that applies to x-ray beams.
Double distance, intensity of beam is now 1/4
X-rays have an Incident Beam, Attenuation, and Scatter - what are the 3 types of Attenuation?
Coherent Scatter 7%
Photoelectric absorption 27%
Compton scattering 57%
A Coherent Scatter is the change in direction of a photon, a Compton Scatter involved both a ______, like Photoelectric Absorption, and a scattered photon of _____ energy
Different tissues have different Radiosensitivities, so effective dose is a calculation of radiation type and tissue type to determine risk of cancerous formation
X-rays travel at the speed of light and have no ______ and no ______
X-rays cause fluorescence and ionization
Males have a higher chance of developing cancer throughout life
44% vs 37%
Ionizing Radiation is able to remove what?
Orbital e- from atoms
Radiation exposure is measured in what?
What is used to compare the biologic effects of different types of Radiation?
Equivalent dose = REM - roentgen equivalent man
Sievert (Sv) = 100 rems
The Effective dose expresses radiation risk to the whole body even though whole body was not exposed and sums the Equivalent dose to each tissue/organ and a tissue weighting factor
The amount of radiation on the skin (Skin Entrance Dose) is the same as the Effective Dose
The amount of radiation incident on an organ:
Radiation absorbed by tissue:
Biological comparison of different Radiation types on different Tissues:
What dose is used to estimate radiation risks, compares radiosensitivities, weighting factors and is calculated in Sieverts?
Salivary Glands are highly Radiosensitive
*down around skin
**bone marrow highest
Example of a Direct radiation effect:
Example of an Indirect radiation effect:
alters structure/function of molecule ***(1/3)
water ionization - free radical ionization
Indirect Attack causes ____ of DNA damage
The cell killing is Dental Radiography can be described as...
The primary risk from dental radiography is the unlikely chance of radiation-induced cancer
What are the critical organs affected by Radiation?
The Effective Dose, based on tissue type, is measured in what?
Deterministic effects are caused by Lethal DNA damage and cell death, while Stochastic effects are based on what?
*leukemia, thyroid cancer, etc
Bone marrow, testes, _____, ______, and _____ are highly radiosensitive organs.
Neurons and muscle have Low Radiosensitivity
Radiation is a weak mutagen and there is no evidence for a dose ______
*damage possible at any dose
Germ cell mutations arising from radiation are possible, but have not been observed in humans
*Hiroshima/Nagasaki didn't pass on defects
Radiation might activate latent carcinogenic viruses or create conditions that favor tumor growth
The most radiosensitive cells tend to have high mitotic rates, undergo many future mitoses, and are the most primitive in differentiation.
What are the two exceptions?
The most radiosensitive tissue is Bone Marrow, what is the least?
Cells are most radiosensitive at mitosis and least sensitive during what phase?
The average energy released from ionization and excitation to absorbing medium per unit track length:
*most widely used term for comparisons of the quality of different radiations
Linear Energy Transfer (LET)
X-rays have ___ LET, while Alpha particles and Neutrons have ____ LET
High LET radiation tends to generate clustered DNA damage, while low LET radiation creates isolated lesions on DNA
100 Gy, death in 1 to 2 days by:
10 Gy, death in 5-10 days by:
2-5 Gy, death in 3 weeks by:
2 Gy exposure will result in Transient ______ in hours and last 1 -2 weeks
focused 10 Gy can result in Dry _______
above 15 Gy ______
When during a lifetime is cancer more likely to be fatal?
*changes around 30
A fetal dose of radiation can double cancer rates
Dental radiographs have a scatter dose to a fetus that is indistinguishable from background radiation
*therefore, cannot produce birth defects (this is motivated reasoning, but whatever)
Rectangular Collimation can decrease the radiation dose by how much?
What is the term that expresses the "one in a million" chance of things?
Dental x-rays are ___ mrem
NY to Cal flight ___ mrem
background radiation ___ mrem/yr
Long plane flight = 1 Micromort
The average man in his 50's has a ____ micromort day risk
Average woman in her 50's has ___ micromort day
400 million x-rays taken/year in the US, How many dental?
Of all the Ionizing Radiation a person receives a year in the US about ____ is background and ____ is medical
What % is Dental?
Because the effects of ionizing radiation at low doses are not fully understood, what concept is invoked?
as low as reasonably achievable
What is the Maximum permissible dose of whole body radiation/year?
Lens of eyes?
All other specific areas of the body?
The MAD - maxi accumulated dose is 10 mSv x Age
F speed film reduces radiation by:
Rectangular Collimation reduces dose by:
Exposures should use Thyroid Collars and be at w/ _______ kVp
The image receptor holding device is more accurate and reduces image retakes
Aluminum absorbs low energy photons, what absorbs highest and lowest energy?
Rare earth metals
The focal spot receptor distance can reduce skin dose when moving closer
What distance should personnel be from the radiation source?
*behind lead glass window or mirror
Large pts increase exposure time by ___%
Small/child/edentulous pts decrease by ___%
Intensity = 1/D squared
Inverse Square Law
What is the Maximum Allowable radiation dosage from diagnostic radiography?
A Lithium fluoride crystal can be used as a Personnel Monitoring Device
Rapid and accurate diagnosis is usually most beneficial to the patient
The average medium FOV CBCT scan carries a ____ micromort risk
Potential risk to a fetus is _______
Fetal exposure is entirely ______
Pregnancy is a Contraindication to diagnostic radiography
Dental radiographic images contribute to _____% of total Exposure from medical imaging
*despite being 1/4 of all medical imaging
5 hr airline flight = 25 uSv or ___ pan and ___ BW's
Average occupational radiation dose is ___% of allowable exposure
There are no limits on the exposure a pt can receive from diagnostics, etc
1 byte = ___ bits
The grayscale puts black at 0 and white at _____
The bit scale is:
(bit depth, gray scale)
What are the 2 types of resolution in Digital imaging?
Spatial - pixels, dpi, etc
Contrast - how many shades
Aside from Spatial and Contrast resolution, the ____ also must have good resolution in digital imaging
What are the 2 types of Digital Detectors?
Photostimulable Phosphor (PSP)
CCD and CMOS sensors are what type?
Intraoral CCD is ____, while intraoral CMOS is ____
Extraoral Solid State detectors can be Digital Direct, Panoramic, or Cephalometric sensors
PSP, Photostimulable Phosphor are the same size as film and disposable
In Storage Phosphor Technology, the Latent Image produced on the plate goes through what?
***definitely on test
Red Laser Scan
The latent image on a ______ can be erased and 100% re-used.
PSP - Photostimulable Phosphor
PSP cycle: Acquisition, ______, view, erase, hygiene
The advantage to CCD/CMOS (solid state) over PSP is what?
The advantage of PSP over CCD/CMOS are what 3 things?
Large exposure latitude
Brightness, Contrast, and Gamma adjustment are types of Digital Processing to enhance image
LUT inversio, Color conversion, and Embossing are all considered "toys" and aren't real image enhancement
Resolution is not that important for detecting dentoalveolar disease, contrast and density play a much larger role.
Most systems have more resolution than the human eye can detect
The Sensor Resolution is ____ Microns (XIOS Plus)
In X-ray film, the ______ is sensitive to x-rays and visible light, and the _____ supports it.
Emulsion is composed of what?
Direct Exposure Film is exposed by X-rays, _____ film is used with intensifying screens and extraoral projections
This type of film is sensitive to what?
Visible light (and x-ray)
How would you know if X-ray film is loaded backwards?
Lead film on back casts pattern and image is light
In an Intensifying Screen, what causes visible light from x-rays?
***The use of Intensifying Screen has what effect on patients?
REDUCES dose of x radiation
Developer, water bath, fixer, water, dry
The _____ converts silver bromide crystals with neutral silver atoms deposited at latent image sites into black, solid silver metallic grains
What removes unexposed, undeveloped silver bromide crystals, leaving the film clear in unexposed areas?
Light, radiopaque areas means:
Dard, radiolucent areas means:
few photons reached film
many photons reached film
Film that is too light can mean what?
Film that is too dark?
Spots on film can be from faulty processing, blurred can be caused by pt. movement
Sharpness can be increased with a small focal spot, increasing distance between _____, and minimizing distance between ______
focal spot and object
object and image receptor
Foreshortening can be caused by not aligning with the _____.
Elongation can be caused by not aligning with the ______
tooth (or other object)
What technique minimizes distortion?
In a tube shift or dual image technique what rule determines where objects are in relation to one another?
Same Lingual, Opposite Buccal
Mesial shift, object moves mesially:
Mesial shift, object moves distally:
rim is radiopaque (3D effect)
The backbone of imaging for the general dentist is Intraoral Radiographic, what are the 3 Categories?
A Full Mouth (FMX) or Complete Mouth Series (CMS) consists of what?
PA's, BW's, and 18 images
The use of correct imaging modalities often excludes cone beam CT, etc
*used intraoral imaging instead
What are the drawbacks to Panoramic imaging?
Large field of view
What are the drawbacks to cone beam CT (CBCT)?
Overlap can be caused by bad angulation of the Tube Head
What method may be useful when the operator is unable to apply paralleling technique for whatever reason?
Bisecting Angle Technique
Position the tube head to the side of the pt that will be radiographed
The open end of the cylinder must be ____ with the guide ring
What are the 6 Rules for Intraoral Imaging
(principles of Dental Imaging)?
Receptor completely covers teeth
Vertical sides of receptor parallel with long axes of teeth
Horizontal sided of receptor parallel with horizontal plane of teeth
Open end cylinder parallel with receptor
Central ray enters Proximal Embrasure at 90 degrees
Central ray directed at center of Receptor
When are Vertical Bitewings used?
*alveolar crest more apical
Occlusal Radiographs can see more structures, are used if pt can't open mouth, can determine locus, and are limited by receptor size
What force carrier particle makes up the x-ray beam?
What has greater energy than x-rays?
Quantum Theory of radiation has been successful in correlating experimental data of what?
Production of X-rays
***polarization, refraction, diffraction all wrong
What % of the kinetic energy of e- that hit the anode are converted to heat?
Increasing the kVp does what 2 things?
Increases # photons and Mean Energy
What is the primary means of dental x-ray attenuation?
Thickness of the mass and energy of the beam
What is the most common type of scattering?
When lower energy photons are removed by aluminum filtration, the mean energy ____, and the beam intensity _____.
Deterministic effects have a ______
Stochastic effects have no _____
What tissue type of the Oral Mucosa is particularly Radiosensitive?
In a child, radiation therapy may destroy what (esp if combined with chemo)
If a pt has head/neck therapy avoid intraoral radiographs for how long?
What organ has the lowest susceptibility to induced cancer?
Most of the radiation the world's population is exposed to comes from what?
Dental x-rays account for less than 1% of the average daily human exposure.
E/F speed is faster than D speed, what has more quality?
State regs require the x-ray beams to be _______ cm or ______ inches to the pts skin surface.
2 3/4 inches
What size dental films is normally used for adult bitewings?
How long can a safe light be used in a dark room before it affects the picture?
Increasing the focal spot of the film distance does what?
Decreases film density
What makes up the Antral Y?
Maxillary sinus and the floor of the nasal cavity
What is above the Maxillary molars on a radiograph?
A "U" shape on every board exam is what?
The Hamulus will be at the same level as the molars
Striations through the Maxillary sinus are what?
Blood vessels in lateral wall
Ridges on the top of the palate: