Radiobiology Flashcards

1
Q

What are the three cardinal principles of radiation protection?

A

Time
Distance
Shielding

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2
Q

What is absorbed dose?

A

mGy/Rad

Radiation the patient has receieved

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3
Q

What is equivalent dose?

A

Incorporates absorbed dose and radiation type
Eqd=AbdxWr
WrXR=1 Wralpha=20

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4
Q

What is the effective dose?

A

mSv/Rem
Incorporates absorbed dose, type of radiation, and the sensitivity of the organ
Represents the stochastic health risk to the whole body
EffD=AbDxWrxWt

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5
Q

What is the minimum distance an operator must stand from the x-ray tube?

A

3 metres unless using appropriate PPE

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6
Q

What is the genetically significant dose?

A

Dose to exposed individuals of reproductive age averaged over the entire population of reproductive age

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7
Q

What does proper use of collimation provide?

A

Reduced off focus radiation

As well as reduced scatter because less tissue is being exposed

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8
Q

What is the purpose of a grid?

A

Minimize scatter reaching the image detector

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9
Q

What is the minimum source to skin distance for mobile radiograpjy?

A

30 cm

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10
Q

How often should collimation and light beam congruency be checked according to SC35?

A

annually

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11
Q

What is positive beam limitation?

A

Radiographer must ensure that collimation is adequate by collimating the radiographic beam so that it is no larger than the IR

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12
Q

What is half value layer?

A

The thickness of a designed absorber required to decrease the intensity of the primary beam to 50% its initial value.
Measured annually in accordance to SC35

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13
Q

What is grid cut off?

A

A decrease in the number of transmitted photons that reach the IR because of some misalignment of the grid

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14
Q

What does off-level grid cut off look like?

A

Decreased density across image

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15
Q

What does off-center grid cut off look like?

A

Decreased density across image

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16
Q

What does off-focus grid cut off look like?

A

Decreased density at edges

17
Q

How often is grid performance checked in accordance to SC35?

A

Annually

18
Q

If a grid is placed upside down, where is grid cutoff on the image?

A

Decreased density at edges of image

19
Q

How often should PPE be examined in accordance with SC35?

A

Annually

20
Q

What does the lead lining in the tube provide?

A

Radiation protection for the patient and imaging personnel from off-focus, or leakage radiation by restricting emission of xrays to area of primary beam

21
Q

What is the minimum SSD for mobile and stationary fluoroscopy?

A

Min. SSD fir stationary is 38cm

Min. SSD for mobile is 30cm

22
Q

What is the entrance skin exposure and what is it measured in?

A

Measurement of radiation output at the point of skin entry for common x-ray, and fluoro procedures. mR, mGy or C/kg

23
Q

How does kVp effect scatter?

A

Increasing kVp inceases scatter to the IR, scatter in general is reduced.

24
Q

What is a controlled area?

A

An area that is occupied only by the occupationally exposed

Dose limit of 20 mSv per year

25
Q

What is an uncontrolled area?

A

An area that is occupied by the public

Dose limit of 1 mSv per year

26
Q

What is the led equivalency for Pb aprons at: 100kVp, 100-150kVp and 150kVp or higher?

A

100kVp- 0.25mmPb
100-150kVp- 0.35mmPB
150kVp or higher- 0.5mmPb

27
Q

What is linear energy transfer?

A

The average energy deposited as ionizing radiation passes through a medium
Ass LET increases chances of biological response increase because more energy is being deposited

28
Q

What is relative biologic effectiveness?

A

The relative capabilities of radiation with differing LETs to produce a particular biological response

29
Q

What is the oxygen enhancement ratio?

A

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

30
Q

What is the oxygen enhancement effect?

A

Oxygen enhances the effects of ionizing radiation on biologic tissue by increasing tissue sensitivity

31
Q

What is indirect ionization?

A

Photon interacts with water, causing ionization which forms free radicals. Free radicals continue to interact with other atoms causing indirect radiation.

32
Q

What is direct ionization?

A

Photon directly interacts with DNA

33
Q

What is deterministic/non-stochastic effect?

A

Severity increases with increased radiation dose

Threshold value exists

34
Q

What is stochastic effect?

A

Incidence increases with increase dose
Linear non-threshold
Usually occurs with low LET rad

35
Q

What dose response relationship does diagnostic radiation follow?

A

Linear non-threshold

no exposure is without risk but small dose has very low risk

36
Q

What are somatic effects?

A

Biological damage from ionizing radiation to body cells

37
Q

What are genetic effects?

A

Stochastic effects from damaged genes