Ch. 8 X-ray emission Flashcards Preview

Bushong Radiology Physics > Ch. 8 X-ray emission > Flashcards

Flashcards in Ch. 8 X-ray emission Deck (35):
1

What is the intensity of the x-ray beam of an x-ray imaging system measured in in air?

mGy(subscript a) formerly milliroentgen

2

What is mGy (air) called?

x-ray quantity

3

x-ray quantity and radiation exposure are both measured in...

mGy (air) or mR

4

mGy measures what in the air?

the number of ion pairs produced in the air by a quantity of x-rays.

5

X-ray quantity is the number of...

x-rays in the useful beam

6

Most general purpose radiographic tubes, when operated at 70 kVp produce x-ray intensities of about...

50 microgray/mAs or 5 mR/mAs at a 100cm SID

7

x-ray quantity is directly proportional to...

mAs

8

formula for relationship of mAs to quantity

I(1)/I(2) = mAs(1)/mAs(2)

9

x-ray quantity is proportional to the square of the ratio of...

kVp

10

formula for relationship of kVp to quantity..

I(1)/I(2) = (kVp(1)/kVp(2))^2

11

to maintain constant exposure of the IR, kVp should increase by ___ and mAs should...

15%, decrease by 50%

12

DESCRIBE inverse square law.

x-ray intensity varies inversely with the square of the distance from the x-ray tube target

13

Formula for inverse square law?

I(1)/I(2) = (d (2)/d (1))^2

14

To maintain constant exposure when SID is increased, mAs should be...

increased by SID^2

15

What is the formula for the square law?

mAs (1)/mAs (2) = SID(1)^2/SID(2)^2

16

DESCRIBE the square law

When SID is increased, mAs must be increased by SID^2 to maintain constant exposure to the IR

17

How much filtration is positioned in the useful beam in a metal filter?

1-5 mm of Al

18

Adding filtration to the useful beam reduces...

patient dose

19

As the energy of an x-ray beam is increased, the penetrability is...

also increased

20

What does penetrability refer to?

the ability of x-rays to penetrate deeper in tissue

21

Penetrability of a beam is also called...

x-ray quality

22

What do not affect radiation quality?

Distance and mAs

23

Attenuation is...

the reduction in x-ray intensity that results from absorption and scattering

24

How is the quality of x-rays measured?

by the HVL.

25

What is the range of the HVL in a diagnostic beam?

3-5 mm Al or 3-6 cm of soft tissue

26

The HVL is the...

thickness of absorbing material necessary to reduce the x-ray intensity to half of its original value.

27

X-ray beam quality can be identified by kVp or filtration, but what is most appropriate?

HVL

28

What can increase x-ray quality?

kVp and Filtration

29

What can increase x-ray quantity?

mAs & kVp

30

What can reduce x-ray quantity?

distance and filtration

31

What has no affect at all on x-ray quality?

mAs & Distance

32

What happens to beam quality and the HVL if kVp is increased?

quality is increased

33

What are the classifications of filtration?

added, inherent, compensating

34

How much filtration is in the inherent classification?

0.5 mm of equivalent Al

35

What is the bow tie filter?

a filter used with CT to compensate the shape of the head or body