Radiation Biology and Protection

Question 1

What is radiobiology?

Answer 1

Study of the effects of ionizing radiation on living systems

Question 2

Initial interation between ionizing radiation and matter occurs at the level of electro within how many seconds after exposure?

Answer 2

10 to the -13 seconds

Question 3

Do all x-rays pass through the patient to get to the receptor?

Answer 3

No

Question 4

What are the two possible effects of some x-rays being absorbed into patient’s tissue?

Answer 4

• Ionization
• Free radical formation

Question 5

Where is DNA located?

Answer 5

Nucleus

Question 6

DNA function?

Answer 6

• Control cell
• Contains hereditary information

Question 7

What is the radiosensitive target molecule?

Answer 7

DNA

Question 8

What part of the cell cycle is most radiosensitive?

Answer 8

• Mitosis
• G2 phase

Question 9

What part of the cell cycle is least radiosensitive?

Answer 9

• G1 phase
• S DNA synthesis period

Question 10

What are the direct biological effects of x-ray exposure?

Answer 10

If radiation is absorbed into biological material, it can interact with the critical target of the cell, leads to biological change

Question 11

Approximately one third of biological effects are from indirect or direct effects?

Answer 11

Direct

Question 12

What are indirect effects of x-rays?

Answer 12

Radiation may interact with other atoms or molecules in the cells, especially water, to produce free radicals

Question 13

What are free radicals?

Answer 13

Atom or molecule carrying an unpaired orbital electron

Question 14

Free radicals have the ability to…

Answer 14

Diffuse and reach far enough to damage the critical structures in the targets or cell

Question 15

What are three ways free radicals achieve stability?

Answer 15

• Recombine without causing changes to biological molecules
• Combine with other free radicals to produce chemical changes
• Combine to produce toxins, H2O2

Question 16

What are deterministic effects?

Answer 16

Killing of large number of cells

Question 17

What are stochastic effects?

Answer 17

Sub-lethal damage to the cell genome

Question 18

What are some examples of deterministic effects?

Answer 18

• Lethal DNA damage
• Cell death
• Reduced in tissue and organ function

Question 19

What are some diseases that are caused by deterministic effects?

Answer 19

• Xerostomia
• Cataracts
• Decreased fetal development

Question 20

What are some examples of stochastic effects?

Answer 20

• Sub-lethal DNA damage
• Gene mutation
• Replication of muted cells

Question 21

What are some diseases that are caused by stochastic effects?

Answer 21

• Leukemia
• Thyroid cancer
• Salivary gland tumors
• Heritable disorders

Question 22

Does deterministic or stochastic effects require a threshold dose?

Answer 22

Deterministic, sufficient cell killing required to produce a clinical response

Question 23

Why does stochastic effects not require a threshold dose?

Answer 23

Single photon can cause changes in DNA

Question 24

Is the severity proportional to the dose in deterministic or stochastic effects?

Answer 24

Deterministic effects

Question 25

What effects are an all or nothing response?

Answer 25

Stochastic effects

Question 26

In deterministic effects, is the probability of having an effect and the dose related?

Answer 26

No, is independent, all individuals show effect when dose is above threshold

Question 27

In stochastic effects, is the probability of having an effect and the dose related?

Answer 27

Yes, frequency of effect is proportional to dose, greater the dose the greater of having an effect is

Question 28

What is radiation induced cancer an effect of?

Answer 28

Stochastic effect

Question 29

What is mucositis from radiation therapy an effect of?

Answer 29

Deterministic effects

Question 30

What organs are have a low radio sensitivity?

Answer 30

- Neurons - Muscles

Question 31

What organs are have a high radio sensitivity?

Answer 31

- Lymphoid organs - Bone marrow - Testes - Intestine - Mucous membrane

Question 32

What is the average dose in dental x-rays for occupationally exposed individuals?

Answer 32

0.2mSV-1% of the allowable dose

Question 33

Is there a limit on exposure a patient can receive for diagnostic imaging?

Answer 33

No

Question 34

Justification principle in radiation protection?

Answer 34

Identifying a situation where the benefit to patient from diagnostic exposure likely exceeds the risk of harm

Question 35

Optimization principle in radiation protection?

Answer 35

Dentist should use every reasonable means to reduce unnecessary radiation exposure to their patients, staff, and themselves

Question 36

ALARA

Answer 36

As low as reasonably achievable

Question 37

Dose limitation principle in radiation protection?

Answer 37

Exposure should be limited to occupational and the public, applied to dentist and their staff

Question 38

Aluminum filter function

Answer 38

Remove low energy photons

Question 39

How does an aluminum filter affect beam intensity and mean energy?

Answer 39

- Beam energy decreases - Mean energy increases

Question 40

Less than 50 kVp requires what type of aluminum filter?

Answer 40

0.5mm

Question 41

50 to 70 kVp requires what type of aluminum filter?

Answer 41

1.5 mm

Question 42

Greater than 70 kVp requires what type of aluminum filter?

Answer 42

2.5 mm

Question 43

What are the two types of collimation?

Answer 43

Round and rectangular

Question 44

What is collimation?

Answer 44

Metallic barrier with hole in the middle to restrict the size of the beam

Question 45

What PID is preferred for dental?

Answer 45

Rectangular

Question 46

What is the maximum recommended beam collimation in diameter?

Answer 46

2.75 inches

Question 47

What does low kVp generate?

Answer 47

Low energy photons

Question 48

Do low energy photons contribute to images?

Answer 48

No

Question 49

Does a long PID/focal length increase or reduce effective dose?

Answer 49

Reduce

Question 50

Does a long PID/ increased focal length make the image more or less sharp?

Answer 50

More sharp

Question 51

Should you stand in the primary beam?

Answer 51

No

Question 52

Where should the provider stand during x-rays?

Answer 52

- 6 ft away 90 to 135 degrees to the primary beam

Question 53

Should you hold the film in the patient's mouth for them?

Answer 53

No