beam restriction

Question 1

what is the purpose of beam restriction

Answer 1

patient safety (smaller field size irradiates less, tfr lower dose)

Question 2

how does beam restriction help image quality

Answer 2

less tissue means less scatter
higher subject contrast
higher image quality

Question 3

at what angle is the mirror

Answer 3

45

Question 4

what distance does the bulb have to be from the mirror

Answer 4

the same distance as the focal spot is from the mirror

Question 5

what happens when the build is too close to the mirror

Answer 5

light beam > x-ray beam

Question 6

what happens when the bulb is too far from the mirror

Answer 6

light beam < x-ray beam

Question 7

how do you check the accuracy of the light beam collimator

Answer 7

with a 9 penny test

Question 8

what is the limit for misalignment in a 9-penny test

Answer 8

up to 2% of SID

Question 9

what is positive beam limitation

Answer 9

limits the size of collimation to the size of the IR

Question 10

if the 9 penny shows too many what is the issue

Answer 10

the bulb is too far

Question 11

if the 9 penny doesnt show enough then what’s the issue

Answer 11

bulb is too close