W2

Question 1

Describe the History of Dental Radiology in brief

Answer 1

X-rays…
* Discovered by Professor Wilhelm Conrad Roentgen in 1895. Named them, Unknown rays (X-rays). published the article on X-rays on 5th Jan, “A Sensational Discovery”
* 2 weeks after Roentgen’s publication Dr Otto Walkhoff made the first picture of teeth - intraoral radiograph after an exposure of 25 min.
* Dr Edmund Kells - FIRST to expose dental radiograph in the United States

Question 2

Describe the Atomic structure

Answer 2

7 protons (postitive charge) and 7 neutrons (neutral charge) in the nucleus
7 electrons (negative charge) orbiting around the nucleus

number of electrons = number of protons in an atom = atom has no net charge/electrically neutral

Question 3

Define electromagnetic radiation and list the types (including x-rays)

Answer 3

Electromagnetic radiation: movement of energy through space as a combination of electric and magnetic fields
Types: X-ray, radiowaves, visible light, microwaves and gamma rays, travel at the speed of light (3X10^8m per second)

Question 4

What is Electrostatic force?
Will electrons closer to the nucleaus have greater or less electrostatic force?

Answer 4

Attraction between the positive protons and negative electrons
Electrons in the orbit closest to the nucleus (the K-shell) will have a greater electrostatic force.

Question 5

What is radiation? List the two types.

Answer 5

Radiation is the transmission of energy through space and matter
1. Particulate radiation: Alpha particles, Betaparticles and cathode rays
2. Electromagnetic radiation

Question 6

What is ionisation and ionisation energy? How does it occur?

Answer 6

If an atom loses an electron, the nucleus becomes a positive ion and the free electron a negative ion = process of forming an ion pair = ionization.
Binding energy (ionization energy); is the amount of energy required to overcome the electrostatic force to remove an electron from its orbit

Question 7

What does the left side and right side represent on this electromagnetic spectrum?

TEST

Answer 7

Ionising radiation = LEFT SIDE (strong waves, short wavelength, high freq., high penetrating ability = easily ionise)

Non-ionising radiation = RIGHT SIDE (long wavelength, low freq., low penetrating ability)

Question 8

Compare Ionizing and Non-ionizing radiation

Answer 8

Ionizing radiations - Radiation consisting of particles, X-rays, or gamma rays with sufficient energy to cause ionization in the medium through which it passes.
Nonionizing radiations - ex. visible light, infrared, and microwave radiation, and radio waves do not have sufficient energy to remove bound electrons from their orbitals.

Question 9

What does wavelength, frequency, distance and energy represent in electromagnetic radiation,

Answer 9

The wavelength (W) is the distance from the crestof one wave to the crest of the next wave.
The frequency (F) is the number of waves in a given distance (D).
Energy of a wave of electromagnetic radiation represents the ability to penetrate an object. Shorter W = greater energy

top wave above has a shorter wavelength, higher frequency and greater energy than the wave below it

Question 10

Explain the characteristics of an X-ray

Answer 10

• X-rays are high energy waves, with very short wavelengths (0.1 – 0.001 nm), and travel at the speed of light.
• X-rays have no mass (weight) and no charge (neutral).
• You cannot see x-rays; they are invisible.
• X-rays travel in straight lines;
• X-rays are differentially absorbed by the materials they pass through.
• X-rays will cause certain materials to fluoresce (give of flight)
• X-rays can be harmful to living tissue. therefore keep the number minimum

Question 11

What does it mean by X-rays are differentially absorbed by the materials they pass through.?

Answer 11

More dense materials (like an amalgam restoration) will absorb more x-rays than less dense material (like pulp tissue)

Question 12

List the three basic components of an X-ray

Answer 12

the X-ray tubehead, which produces the x-rays
Support arms, which allow you to move the tubehead
The control panel, which allows you to alter the duration of the x-ray beam (exposure time)

Question 13

List the components of an x-ray tube

Answer 13

1. Focusing cup (Molybdenum): focuses electrons on target
2. Tungsten Filament: releases electrons when heated
3. Electron stream: electrons cross from filament to target
4. Vacuum: to prevent collision of the moving electrons with gas molecules which can reduce the speed of electrons & prevents oxidation and burnout ofthe filament.
5. Tungsten Target: x-rays produced when electrons strike target
6. Copper stem: Houses the target and helps remove heat from target
7. Leaded glass: Keeps x-rays from exiting tube in wrong direction
8. **X-rays **produced in target are emitted in all directions
9. Beryllium window: this non-leaded glass allows x-rays to pass through. The PID would be located directly in line with this window

Question 14

What parts of the x-ray tube make up the cathode and anode.

Answer 14

Cathode = Negatively charged
Anode = Positively charged

Question 15

What is thermionic emission?

Answer 15

When we depress the exposure button -> electricity flows through the filament -> hot -> electrons released

Question 16

Why is the target made of Tungsten?

Answer 16

Tungsten = Only metal that has high atomic number, high melting point, high thermal conductivity and low vapor pressure

Question 17

Describe the Line Focus Principle

Answer 17

target is placed at an angle of 20 degree to the X-ray beam = smaller source of X-rays and sharper image

Question 18

Compare the two types of x-rays that are produced

Answer 18

Two types of x-rays produced in the target of the x-ray tube…
1. Bremmstrahlung/general radiation (majority): high-speed electrons pass close to, or strike, the nuclei of the target atoms. Electrons are slowed down and change direction = E released in form of X-rays
The higher the speed of the electrons, the higher the average energy of the x-rays produced
2. Characteristic radiation: High energy electron hits inner most electron (K shell) knocking off the electron. The elctron from L takes its place. The energy of X-Ray will be equal to the difference between the binding energies of the target electrons involved

Question 19

What are the three factors that absorb the excess heat produced by X-rays?

Answer 19

High melting point of tungsten target
Conductive properties of copper stem
Oil surrounding X-ray tube

Question 20

List the factors controlling X-Ray beam

Answer 20

kVp control: increase = number of X-rays and kinetic energy (greater penetration and contrast)
mA setting: increase = increase number of X-rays (sharper)
Exposure time: increase = increase number of X-rays (sharper)
Filtration: = only high energy X-rays
Collimation = reduce radiaton scope

Question 21

Describe the three filters used in Inherent filtration. Describe the factor needed to achieve total filtration

Answer 21

Beryllium window, oil surrounding tube head, barrier material
= filter low energy X-rays = High E X-rays

Sometimes manafacture can add filter of Al = Total Filtration

Question 22

What is collimation?

Answer 22

metallic barrier (lead disc) with anaperture in the middle used to reduce the size of the X-ray beam and therefore the volume of the irradiatedtissue in a patient

Question 23

Explain the Interaction of X-Rays with matter

Answer 23

90% of X-Rays get absorbed
B - Of the absorbed X-rays, 70% undergo scattering within the tissues (compton and coherent scattering). These scattered radiations reach the film and degrade the image quality
C - The rest 30% of absorbed X-rays are critical in diagnostic imaging. More X-rays are absorbed by bone (causing bone to appear white on radiograph) than by soft tissues (which appear dark in radiograph)
(A) - 10% directly reach the film without interacting with the tissues

Question 24

Define Attenuation and list and describe the three ways in which it can occur.

Answer 24

Attenuation = Reduction of x-ray beam intensity (thatr eaches film) by interaction with matter (tissues)
It occurs by…
1. Coherent scattering: X-ray beam hits outer shell electron causing vibration (8%)
2. Compton scattering: X-ray beam knocks out outer shell electron (62%)
3. Photoelectric absorption: X-ray beam knocks out innermost electron and electron from next shell drops to fill vacency (30%)

Question 25

How does **Ionizing radiation cause damage**? | 2 ways

Answer 25

**Direct effect**: Energy of photon is transferred directly to biological macromolecules (DNA/RNA) **Indirect effect**: 75% of our cells contain H20. Radiolysis of water (Radiation interacts with H2O = **H2O2 (Hydrogen peroxide)** = damage the cell by breaking down proteins or DNA) | **TEST**

Question 26

Radiation effects at **cellular level**

Answer 26

Effect on... * **Proteins**: Changes in the secondary and tertiary structure, disruption of the side chains, breakage of hydrogen and sulfide bonds * **Nucleus**: DNA - change or loss of base, disruption of Hydrogen bonds, breakage of DNA strands. * **Chromosomes**: type of damage that is visualized depends on stage of cell cycle * **Cytoplasm**: high doses are required to cause visible damage = increased permeability to Na and K = changes in cellular mechanisms * **Mitosis**: delayed mitosis * **Cell death** * **Cell recovery**

Question 27

List the three radiation effects at **tissue and organ level** ## Footnote TEST - 3 effects of radiation on tissue

Answer 27

Deterministic effects => Somatic Deterministic effects Stochastic effects => Somatic Stochastic effects OR Genetic stochastic effects

Question 28

Define **Somatic Deterministic effects** and list examples

Answer 28

Damaging effects to the body of the person exposed that will **definitely** result from **high dose radiation** * threshold dose below which there will be no effect * Severity of effect is directly proportionate to the dose of radiation * Ex. Radiotherapy -> Skin reddening, Cataract, **Mucositis**

Question 29

Effects of **Radiotherapy** on **oral cavity** ## Footnote TEST?

Answer 29

Question 30

Can **somatic deterministic effects** be seen with Dental Radiology?

Answer 30

No somatic deterministic effects due to small dose (well below threshold)

Question 31

Define **Somatic Stochastic effects** and list examples ## Footnote TEST

Answer 31

Effects (carcinogenesis) that **may** (**probability** of occurrence) develop as a result of exposure to radiation Probability of getting cancer depends on amount of radiation exposure. Higher the dose = higher probability of getting a cancer. * There is no threshold dose * Severity of effect is not proportionate to the dose of radiation Ex. Japanese atom bomb survivors developed cancer, irradiation treatment for postpartum mastitis

Question 32

Since there is no evidence of a lower threshold for the appearance of Somatic Stochastic Effects, the prudent course of action is to ensure that all radiation exposures follow a principle known as....

Answer 32

ALARA (As Low As Reasonable Achievable) Effects of Diagnostic dose (very low) of radiation ‐ eg ‐**Dental X‐Ray radiation** is not much but considered as a **risk factor** therefore avoid unnecessary exposure of radiation to patients therefore **avoid unnecessary exposure of radiation to patients**

Question 33

Are **pregnant patients** able to have intraoral X-rays?

Answer 33

should have radiographs taken **if and only if absolutely indicated for diagnosis** by *weighing the advantages and disadvantages** **However radiation protection measures should be taken** for pregnant patients **especially in the 1st and 3rd trimester** to avoid risk to the unborn | No contraindicated, make assessment if necessary

Question 34

Define **Genetic Stochastic effects** and list examples

Answer 34

Effects due to **Mutation in gene/chromosome of a germ cell** (sperm or ovum) Radiation to the reproductive organs may damage the DNA of germ cell and result in congenital abnormality of the offspring

Question 35

Describe the consideration of **Genetic Stochastic effects** in Dental Radiology

Answer 35

No much effect, since dental radiography does not involve irradiating the reproductive organs. BUT STILL THERE MAY BE A RISK OF SCATTERED RADIATION TOTHE REPRODUCTIVE ORGANS. Hence all radiation exposures should **follow ALARA principle**

Question 36

List the various **radio-sensitivity** of different **tissues**/**organs**

Answer 36

High = high mitotic activity (cell division)

Question 37

Describe the different **direct effects** of radiation on **somatic cells** vs **reproductive stem cells**.

Answer 37

If the radiation hits somatic cell = radiation induced malignancy If the radiation hits reproductive stem cell = radiation induced congenital abnormality

Question 38

Describe **Acute Radiation Syndrome**

Answer 38

Effects of **whole body irradiation** **Somatic Deterministic effect** Collection of signs and symptoms experienced by humans exposed by **medical radiotherapy, atom bomb blastsand radiation accidents**.

Question 39

What dose of radiation produces harmful effects?

Answer 39

Any exposure, however small it may be,can produce harmful effects

Question 40

Describe the two sources of radiation

Answer 40

Question 41

What is **Dosimetry**?

Answer 41

Determining the **quantity** of radiation exposure or dose

Question 42

Define **exposure**

Answer 42

Measure of ability of radiation to produce ionization in air

Question 43

What is the **absorbed dose?**

Answer 43

measure of the energy deposited in a medium by ionizing radiation per unit mass - depends on absorbing medium Eg. X-ray beam maydeposit four times more dose in bone than in air *Used to estimate the risk of acuteradiation syndrome* | SI Unit – Gray(Gy)

Question 44

What does the **Equivalent dose** represent?

Answer 44

Used to compare the biologic effects ofdifferent types of radiation on a tissue or organ *Equivalent dose = Absorbed dose X RadiationWeighing factor(WR)*

Question 45

What does the **SI unit** stand for?

Answer 45

SI Unit = Sievert (Sv)

Question 46

What does the **Effective dose** represent?

Answer 46

**measure of the cancer risk** to a whole organism due to ionizing radiation delivered non-uniformly to part(s) of its body * It takes into account both - the type of radiation and the type and amount of tissue exposed *Effective dose = Equivalent dose X Tissue Weighing factor (WT )*

Question 47

What does tissue Weighing factor (WT) represent?

Answer 47

Determined based on **sensitivity of organs to radiation**. More the Weighing factor more the risk of cancer

Question 48

What does the **Collective effective dose** represent?

Answer 48

Measure used when considering the total effective dose to the population from a particular source of radiation *Collective effective dose = Effective dose X population*

Question 49

What does **ARPANSA** stand for?

Answer 49

Australian Radiation Protection and Nuclear safety agency (ARPANSA)

Question 50

What are the **dose limits** according to ARPANSA ## Footnote Impt.

Answer 50

- Dose limits for Public – **1 mSv in a year** averaged over a period of 5 consecutive calendar years - Dose limits for Occupational – **20 mSv per year**, averaged over a period of 5 consecutive calendar years - Dose limits for pregnant dental practitioner – **1mSv**

Question 51

**The degree of risk from radiation can beexpressed in 2 ways:** 1) Equivalent natural exposure 2) Probability of stochastic effect Describe the equivalent natural exposure for bitewings and OPG

Answer 51

* 2 **bitewings** – 0.004 mSv – approximately thesame as 2 hours on a plane * **OPG** – 0.007 mSv – approximately the same asjust over 3 hours on a plane

Question 52

Is the statement "having 2 intraoral radiographies = 1/2 million risk of cancer" considered to be 1) Equivalent natural exposure 2) Probability of stochastic effect

Answer 52

2) Probability of stochastic effect

Question 53

What is the **Objective of Radiation protection**

Answer 53

To provide an appropriate standard of protection for man without unduly limiting the beneficial practices giving rise to radiation exposure

Question 54

List the three guiding principles in radiation protection

Answer 54

* **Principle of justification** - do more good than harm. In practice thisprinciple influences what patients we select for radiographicexaminations and what examinations we choose * **Principle of optimization** - use every means to reduce unnecessaryexposure to their patient and themselves – ALARA Principle * **Dose limitation** - for occupational and public exposures to ensure that noindividuals are exposed to unacceptably high doses

Question 55

Describe Radiation protection for **the Patient**

Answer 55

* No unnecessary radiographs * Only advised after taking detailed history, a thorough clinical examination and considering dental and general health needs of the patient * Optimization: reducing the exposure as much as possible - proper settings and technique * Avoid repeats: Adequate training, technique, handling, processing, interpretation and documentation of findings * Equipment Reliability: functioning properly, settings for the exposure factors (exposuretime, mA, kVp) * Lead barriers ie, apron (thickness .25mm) * Pregnancy Precautions: ask, avoid, shield

Question 56

Describe Radiation protection for **the Operator**

Answer 56

**Time – Distance – Shielding principle** * Reduce the exposure time * Increase distance from the source * Shielding using lead barriers and room (thick wall, concrete, barium, plaster, lead) * Never hold the film for the patient during exposure, parent or individuel with lead apron * Wear your exposure badge and check the exposure report monthly

Question 57

Describe Radiation protection for **the Public**

Answer 57

* Never allow other people * X ray beam to be directed towards the outside wall * Hazard light and sign on the door

Question 58

What are the **Responsibilities of a Clinician**

Answer 58

* Ensure if radiograph is really indicated * Use the best radiographic technique * Proper processing * Interpretation of radiographs to be shared with Dento-maxillofacial Radiologist * Maintain radiographic records

Question 59

Describe the **Radiation safety Act 1999**

Answer 59

Regulations relating to **dental radiography** * Dispose & Relocate: notification of disposal and application to relocate out of state * Monitoring badges: Extra-oral - based on work-load (justify in plan) * Radiation Safety Officer: possession licensee unless the possession licensee is a company * Radiation Safety Plan: Radiation Safety and Protection Plan (RSPP) is adocument submitted by a possession licence applicant to ensure that persons and the environment, are protectedfrom the harmful effects of radiation * Radiographic Record (Log Book) * Audits: examining log books, lead aprons, x-ray equipment.

Question 60

Who can get a **license**

Answer 60

* Registered dentists * Registered oral health therapists * Registered dental therapists * Registered dental hygienists * Dental assistants * Student dental assistants * Student dental practitioners

Question 61

What are the **details required for the radiographic record (log book)**

Answer 61

* Date radiograph taken * Name of patient * DOB of patient * Gender of patient * Name of radiographer * Type of radiograph * Exposure factors (unless standard)

Question 62

What is **Dosimetry**?

Answer 62

Determining the **quantity** of radiation exposure or dose

Question 63

What dose of radiation produces harmful effects?

Answer 63

Any exposure, however small it may be,can produce harmful effects

Question 64

Describe the two sources of radiation

Answer 64

Question 65

What does the **absorbed dose** represent?

Answer 65

measure of the energy deposited in a medium by ionizing radiation per unit mass - depends on absorbing medium Eg. X-ray beam maydeposit four times more dose in bone than in air *Used to estimate the risk of acuteradiation syndrome* | SI Unit – Gray(Gy)

Question 66

Define **exposure**

Answer 66

Measure of ability of radiation to produce ionization in air

Question 67

What dose of radiation produces harmful effects?

Answer 67

Any exposure, however small it may be,can produce harmful effects

Question 68

Describe the two sources of radiation

Answer 68

Question 69

What is **Dosimetry**?

Answer 69

Determining the **quantity** of radiation exposure or dose

Question 70

Define **exposure**

Answer 70

Measure of ability of radiation to produce ionization in air

Question 71

What does the **absorbed dose** represent?

Answer 71

measure of the energy deposited in a medium by ionizing radiation per unit mass - depends on absorbing medium Eg. X-ray beam maydeposit four times more dose in bone than in air *Used to estimate the risk of acuteradiation syndrome* | SI Unit – Gray(Gy)

Question 72

What dose of radiation produces harmful effects?

Answer 72

Any exposure, however small it may be,can produce harmful effects

Question 73

What does the **absorbed dose** represent?

Answer 73

measure of the energy deposited in a medium by ionizing radiation per unit mass - depends on absorbing medium Eg. X-ray beam maydeposit four times more dose in bone than in air *Used to estimate the risk of acuteradiation syndrome* | SI Unit – Gray(Gy)

Question 74

Define **exposure**

Answer 74

Measure of ability of radiation to produce ionization in air

Question 75

What is **Dosimetry**?

Answer 75

Determining the **quantity** of radiation exposure or dose

Question 76

Describe the two sources of radiation

Answer 76

Question 77

Define **exposure**

Answer 77

Measure of ability of radiation to produce ionization in air

Question 78

Describe the two sources of radiation

Answer 78

Question 79

What does the **absorbed dose** represent?

Answer 79

measure of the energy deposited in a medium by ionizing radiation per unit mass - depends on absorbing medium Eg. X-ray beam maydeposit four times more dose in bone than in air *Used to estimate the risk of acuteradiation syndrome* | SI Unit – Gray(Gy)

Question 80

What is **Dosimetry**?

Answer 80

Determining the **quantity** of radiation exposure or dose

Question 81

What dose of radiation produces harmful effects?

Answer 81

Any exposure, however small it may be,can produce harmful effects