Radiation Units & Quantities (CTBC 21) Flashcards

1
Q

2 means of measuring x-rays

A

Radiation in Air
Radiation in Tissue

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2
Q

Exposure

A

Number of ionizations created in air

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3
Q

Units of Exposure

A

Coulombs per kilogram (C/kg)

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4
Q

6.242x10^18 ionizations equals

A

1 coulomb

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5
Q

Traditional units of radiation measurement

A

Roentgens (R)
(more common in practice)

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6
Q

2.58 x 10^-4 C/kg

A

1 Roentgen

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7
Q

Typically the exposure in air created by CT is significantly less than…

A

1C/kg or 1R
(1 C/kg ~ 3876 R)

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8
Q

(air) KERMA

A

Kinetic Energy Released per unit MAss
(Alternative to measuring exposure)

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9
Q

Air kerma quantifies radiation by measuring

A

Energy of ionizations

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10
Q

Ionizations

A

Liberated electrons

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11
Q

Air kerma measures _____ of ionizations; Exposure measures _______ of ionizations

A

energy
number

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12
Q

Air Kerma Units

A

Gy
mGy

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13
Q

Both _______ and _______ can be used to measure radiation produced by CT x-ray tube, scatter radiation produced during CT procedure, scatter radiation escaping CT scan room

A

Exposure
Air kerma

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14
Q

Measuring the radiation produced by a CT x-ray tube is readily done with

A

Exposure or Air Kerma

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15
Q

Measuring the scatter radiation produced during a CT procedure is readily achieved using

A

Exposure or Air Kerma

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16
Q

Measuring the scatter radiation escaping the CT scan room is readily achieved using

A

Exposure or Air Kerma

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17
Q

Increasing mA _______exposure and air kerma

A

Increases

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18
Q

Increasing kVp _______ exposure and air kerma

A

Increases

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19
Q

The most basic way to quantify the amount of radiation energy absorbed by the body

A

Absorbed dose (D)

20
Q

Units for absorbed dose (D)

A

Gy/mGy
(Rad/mRad)

21
Q

1 J/kg =

A

1Gy

22
Q

An extension of absorbed dose measured in Sv/mSv (rem/mrem)

A

Equivalent dose (EqD)
(EqD = D x Wr)

23
Q

Wr (W-subR)

A

Radiation weighting factor: used to define difference in biological damage between different radiation types

24
Q

Wr (W-subR) for x-rays

A

1

25
Q

Wr (W-subR) for gamma rays

A

1

26
Q

Wr (W-subR) for beta particles

A

1

27
Q

Wr (W-subR) for protons

A

5

28
Q

Wr (W-subR) for slow neutrons

A

5

29
Q

Wr (W-subR) for fast neutrons

A

10

30
Q

Wr (W-subR) for alpha paticles

A

20

31
Q

Because CT utilizes x-rays, the EqD is always equal to _______ x D

A

EqD = (1)D

32
Q

In CT the difference between EqD and D is

A

Units: Sv vs Gy

33
Q

EfD
(equation)

A

Effective Dose
EfD = (D)(W-subR)(W-subT)

34
Q

Purpose of EfD

A

Accounts for specific radiosensitivities of different tissue types

35
Q

Wt (W-subT) for bone marrow

A

0.12

36
Q

Wt (W-subT) for breasts

A

0.12

37
Q

Wt (W-subT) for lungs

A

0.12

38
Q

Wt (W-subT) for colon

A

0.12

39
Q

Wt (W-subT) for stomach

A

0.12

40
Q

Wt (W-subT) for gonads

A

0.08

41
Q

Wt (W-subT) for liver

A

0.04

42
Q

Wt (W-subT) for thyroid

A

0.04

43
Q

Wt (W-subT) for brain

A

0.01

44
Q

Tissue weighting factors (Wt (W-subT)) represents the comparative risk of

A

Developing radiation-induced cancer

45
Q

Describes the biological effect of a given dose of radiation

A

Equivalent dose (EqD)
(EqD = D x Wr)