Factors controlling the X ray beam intensity

Question 1

what is intensity

Answer 1

total amount of energy contained in the X ray beam

Question 2

what is the formula for calculating intensity

Answer 2

quantity x quality

Question 3

define quantity

Answer 3

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

Question 4

what is quantity expressed as

Answer 4

tube current (mA) x time (sec) -> mAs

Question 5

what is quality

Answer 5

average energy of the x ray beam

Question 6

what is quality controlled by

Answer 6

the tube voltage

Question 7

X ray beam is _____

Answer 7

heterogeneous

Question 8

what are the factors controlling the X ray beam intensity

Answer 8

• tube voltage
• exposure time
• tube current
• filtration
  -collimation
• source receptor distance

Question 9

as the tube voltage increases:

Answer 9

• number of photons generated increases (increased quantity)
• mean energy of photons increases (increased quality)
• maximum energy of photons increasesw

Question 10

as exposure time increases:

Answer 10

• number of photons generated increases (increases quantity)
• mean energy of photons is unchanged (quality unchanged)
• maximum energy of photons is unchanged (quality unchanged)

Question 11

as mA increases:

Answer 11

• the number of photons generated increases (icnreased quantity)
• mean energy of photons is unchanged (quality unchanged)
• maximum energy of photons is unchanged (quality unchanged)

Question 12

what does filtration do

Answer 12

selectively removes long wavelength (low energy) X rays

Question 13

what is involved in inherent filtration

Answer 13

• glass envelope
• immersion oil
• metal housing
• tube window

Question 14

what is involved in added filtration

Answer 14

aluminum disks

Question 15

how is total filtration calculated

Answer 15

inherent filtration + added filtration

Question 16

as filtration increases:

Answer 16

• the number of photons decreases (reduced quantity)
• mean energy of photons increases (increases quality)
• maximum energy of photons is unchanged

Question 17

what does collimation do

Answer 17

restricts the size and shape of the beam
- number of photons decreases
- mean energy of photons in unchanged
- maximum energy of photons is unchanged

Question 18

as source to receptor distance increases:

Answer 18

• number of photons decreases (decreased quantity)
• mean energy of photons in unchanged (unchanged quality)
• maximum energy of photons is unchanged

Question 18

what is the inverse square law

Answer 18

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

Question 19

what is density altered by

Answer 19

factors affecting quantity of the beam

Question 20

what is contrast altered by

Answer 20

factors affecting quality of the beam

Question 21

the amount of blackness of an image is related to what?

Answer 21

how many x rays reach the receptor

Question 22

why is density controlled by mAs

Answer 22

because increasing mAs and kVp will increase the quantity and increasing quantity more x rays will reach the receptor -> the darker the image will be -> higher density

Question 23

what is density primarily controlled by

Answer 23

mAs and less so by kVp

Question 24

what is the mAs rule

Answer 24

mA and exposure time are inversely proportional

Question 25

is mA is increased exposure time must be:

Answer 25

decreased to maintain the same density of the image

Question 26

if mA is decreased exposure time must be ____

Answer 26

increased to maintain the same density of the image

Question 27

what is contrast and what is it controlled by

Answer 27

• the difference in densities between light and dark regions of a radiograph
• mostly controlled by the voltage

Question 28

high contrast ______ kVp

Answer 28

low

Question 29

in high contrast, density differences between adjacent areas are ____, and there are fewer _____

Answer 29

greater; shades of grey