lecture 4 factors affecting xray

Question 1

total amount of energy contained in the x-ray beam

Answer 1

intensity

Question 2

number of photons in the beam. related to tube current(mA) and exposure time and less so by tube voltage

Answer 2

quantity

Question 3

quantity x quality =

Answer 3

intensity of beam

Question 4

how is quantity expressed

Answer 4

mAs

Question 5

average energy the x-ray beam

Answer 5

quality

Question 6

what is controlled primarily by the tube voltage (kVp)

Answer 6

quality

Question 7

x-ray of beam is

Answer 7

heterogeneous

Question 8

6 factors controlling the x-ray beam intensity

Answer 8

1. tube voltage
2. exposure time
3. tube current
4. filtration
5. collimation
6. source-receptor distance

Question 9

as the voltage of the tube increases:
1. number of photons
2. mean energy
3. maximum energy of photons

Answer 9

1. number of photons INCREASES
2. mean energy INCREASES [increases quality]
3. maximum energy of photons INCREASES

Question 10

as the exposure time of the tube increases:
1. number of photons
2. mean energy
3. maximum energy of photons

Answer 10

1. number of photons INCREASES
2. mean energy UNCHANGED [quality unchanged]
3. maximum energy of photons UNCHANGED [quality unchanged]

Question 11

as the tube current[mA] increases:
1. number of photons
2. mean energy
3. maximum energy of photons

Answer 11

1. number of photons INCREASES [increases quantity]
2. mean energy UNCHANGED [quality unchanged]
3. maximum energy of photons [quality unchanged]

Question 12

selectively removes long wavelength (low energy) x-rays

Answer 12

filtration (made of aluminum)

Question 13

total filtration =

Answer 13

inherent filtration + added filtration

Question 14

inherent filtration:
1
2
3
4

Answer 14

1. glass envelope
2. immersion oil
3. metal housing
4. tube window

Question 15

added filtration:
1

Answer 15

1. aluminum disks

Question 16

as filtration increases:
1. number of photons
2. mean energy
3. maximum energy of photons

Answer 16

1. number of photons DECREASES [reduce quantity]
2. mean energy INCREASES [increases quality]
3. maximum energy of photons UNCHANGED

Question 17

this restricts the size and shape of the beam

Answer 17

collimation

Question 18

collimation:
1. number of photons
2. mean energy
3. maximum energy of photons

Answer 18

1. number of photons DECREASES
2. mean energy UNCHANGED
3. maximum energy of photons UNCHANGED

Question 19

intensity of the beam varies inversely to the square of the source-to-receptor distance

Answer 19

inverse square law

Question 20

inverse square law- one method of calculating the new beam intensity when changing the source-to-receptor distance

1. if distance is double 8 to 16:
2. if distance is tripled from 4 to 12:
3. if distance is halved from 16 to 8:

Answer 20

1. new intensity is 1/4(inverse of 2^2)
2. new intensity is 1/9 (inverse of 3^2)
3. new intensity is 4x (inverse of 1/2^2)

Question 21

as source-to-receptor distance increases:
1. number of photons
2. mean energy
3. maximum energy of photons

Answer 21

1. number of photons DECREASES[decreases quantity]
2. mean energy UNCHANGED [unchanged quality]
3. maximum energy of photons UNCHANGED

Question 22

altered by factors affecting quantity of the beam

Answer 22

density

Question 23

altered by factors affecting the quality of the beam

Answer 23

contrast

Question 24

amount of blackness of an image

Answer 24

density

Question 25

with density, the amount of blackness of an image is related to

Answer 25

how many x-rays reach the receptor

Question 26

what is density primarily controlled by and less so by

Answer 26

controlled by mA less controlled by kVp

Question 27

how will density be affected if the amount of mA and kVp are increased

Answer 27

the quantity will be increased -> more x-rays will reach receptor -> darker the image will be (so higher density)

Question 28

what is the mA rule for density

Answer 28

mA and exposure time are inversely proportional

Question 29

for density, if the mA is increased, exposure time must be ______ to maintain the same density of the image

Answer 29

decreased

Question 30

for density, if the mA is decreased, the exposure time must be _____ to maintain the same density of the image

Answer 30

increased

Question 31

the difference in densities between light and dark regions of a radiograph

Answer 31

contrast

Question 32

what is the contrast primarily controlled by

Answer 32

voltage

Question 33

short gray scale: long gray scale:

Answer 33

short gray scale: high contrast long gray scale: low contrast

Question 34

what is the kVp for high contract? wavelength? penetration?

Answer 34

kVp: LOW long wavelengths less penetrating

Question 35

high or low contrast: 1. density differences between adjacent areas are greater; fewer shades of gray

Answer 35

high contrast

Question 36

what is the kVp for low contrast? wavelength? penetration?

Answer 36

high kVp short wavelengths more penetrating

Question 37

high or low contrast? density differences between adjacent areas are more subtle; more shades of gray

Answer 37

low contrast