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ORPT 301 > Radiation Biology and Protection > Flashcards

Radiation Biology and Protection Flashcards

1
Q

What is radiobiology?

A

Study of the effects of ionizing radiation on living systems

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2
Q

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

A

10 to the -13 seconds

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3
Q

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

A

No

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4
Q

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

A
  • Ionization
  • Free radical formation
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5
Q

Where is DNA located?

A

Nucleus

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6
Q

DNA function?

A
  • Control cell
  • Contains hereditary information
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7
Q

What is the radiosensitive target molecule?

A

DNA

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8
Q

What part of the cell cycle is most radiosensitive?

A
  • Mitosis
  • G2 phase
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9
Q

What part of the cell cycle is least radiosensitive?

A
  • G1 phase
  • S DNA synthesis period
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10
Q

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

A

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

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11
Q

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

A

Direct

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12
Q

What are indirect effects of x-rays?

A

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

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13
Q

What are free radicals?

A

Atom or molecule carrying an unpaired orbital electron

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14
Q

Free radicals have the ability to…

A

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

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15
Q

What are three ways free radicals achieve stability?

A
  • Recombine without causing changes to biological molecules
  • Combine with other free radicals to produce chemical changes
  • Combine to produce toxins, H2O2
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16
Q

What are deterministic effects?

A

Killing of large number of cells

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17
Q

What are stochastic effects?

A

Sub-lethal damage to the cell genome

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18
Q

What are some examples of deterministic effects?

A
  • Lethal DNA damage
  • Cell death
  • Reduced in tissue and organ function
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19
Q

What are some diseases that are caused by deterministic effects?

A
  • Xerostomia
  • Cataracts
  • Decreased fetal development
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20
Q

What are some examples of stochastic effects?

A
  • Sub-lethal DNA damage
  • Gene mutation
  • Replication of muted cells
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21
Q

What are some diseases that are caused by stochastic effects?

A
  • Leukemia
  • Thyroid cancer
  • Salivary gland tumors
  • Heritable disorders
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22
Q

Does deterministic or stochastic effects require a threshold dose?

A

Deterministic, sufficient cell killing required to produce a clinical response

23
Q

Why does stochastic effects not require a threshold dose?

A

Single photon can cause changes in DNA

24
Q

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

A

Deterministic effects

25
Q

What effects are an all or nothing response?

A

Stochastic effects

26
Q

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

A

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

27
Q

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

A

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

28
Q

What is radiation induced cancer an effect of?

A

Stochastic effect

29
Q

What is mucositis from radiation therapy an effect of?

A

Deterministic effects

30
Q

What organs are have a low radio sensitivity?

A
  • Neurons
  • Muscles
31
Q

What organs are have a high radio sensitivity?

A
  • Lymphoid organs
  • Bone marrow
  • Testes
  • Intestine
  • Mucous membrane
32
Q

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

A

0.2mSV-1% of the allowable dose

33
Q

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

A

No

34
Q

Justification principle in radiation protection?

A

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

35
Q

Optimization principle in radiation protection?

A

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

36
Q

ALARA

A

As low as reasonably achievable

37
Q

Dose limitation principle in radiation protection?

A

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

38
Q

Aluminum filter function

A

Remove low energy photons

39
Q

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

A
  • Beam energy decreases
  • Mean energy increases
40
Q

Less than 50 kVp requires what type of aluminum filter?

A

0.5mm

41
Q

50 to 70 kVp requires what type of aluminum filter?

A

1.5 mm

42
Q

Greater than 70 kVp requires what type of aluminum filter?

A

2.5 mm

43
Q

What are the two types of collimation?

A

Round and rectangular

44
Q

What is collimation?

A

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

45
Q

What PID is preferred for dental?

A

Rectangular

46
Q

What is the maximum recommended beam collimation in diameter?

A

2.75 inches

47
Q

What does low kVp generate?

A

Low energy photons

48
Q

Do low energy photons contribute to images?

A

No

49
Q

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

A

Reduce

50
Q

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

A

More sharp

51
Q

Should you stand in the primary beam?

A

No

52
Q

Where should the provider stand during x-rays?

A
  • 6 ft away
    90 to 135 degrees to the primary beam
53
Q

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

A

No

ORPT 301 (10 decks)

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