CALCULATIONS & MATH TUTORIALS

Question 1

REMINDER only use inverse square law when ______ and ____ are involved together

Answer 1

distance and dose

Question 2

the radiation beam intensity will ___increase/decrease__ with ___increasing/decreasing__ distance due to the beam’s divergence

Answer 2

beam intensity//dose will decrease with increasing distance, due to beam’s divergence

Question 3

would you use inverse square law or direct proportion to - compare similar triangles, use for field size and SSD, and magnification

Answer 3

direct proportion

Question 4

inverse square law or direct proportions show change in dose with distance

Answer 4

inverse square law

Question 5

T/F: divergence is predictable

Answer 5

true

Question 6

magnification is based on inverse square law or direct proportions?

Answer 6

direct proportions

Question 7

overdose or underdose, we use inverse square law or direct proportion? - commonly phrased “patient was accidentally treated at x distance, or x dose”

Answer 7

inverse square law

Question 8

Mayneord F is a type of direct proportion or inverse square law?

Answer 8

inverse square law

Question 9

for a direct proportion that is a square, you must do the eq once or twice?

Answer 9

once - example 8 x 8

Question 10

for a direct proportion that is a rectangular, you must do the eq once or twice?

Answer 10

twice - example 9.3 x 8

Question 11

according to inverse square law - if you double your dose, what happens to your distance?

Answer 11

quarter your distance

Question 12

according to inverse square law - if you double your distance

Answer 12

Intensity needs to go up by 4

Question 13

if a patient was treated at 109 SSD, instead of 100 SSD… were they overdose or underdosed?

Answer 13

underdosed… we are treating patient further away from source … lowering table

Question 14

we kick the couch to avoid beam divergence and match with the ______

Answer 14

field size

Question 15

ISF stands for what?

Answer 15

Inverse Square Factor

Question 16

Inverse Square Factor only incorporates the Intensity, or Distance?

Answer 16

Distance

Question 17

if it is an under dose … small number goes on top or bottom of ISF?

Answer 17

we want a smaller number as answer, so small number would go on top

Question 18

if it is an over dose … small number goes on top or bottom of ISF?

Answer 18

we want larger number as answer, so larger number would go on top

Question 19

do not forget to _____ distance part of ISF/Inverse Sqaure Law!!!!

Answer 19

square it!

Question 20

for a dose error question - if it is UNDER dose do we want ISF to be greater than, or less than 1?

Answer 20

less than 1

Question 21

for a dose error question - if it is OVER dose do we want ISF to be greater than, or less than 1?

Answer 21

greater than 1

Question 22

________ is the ratio of the size of an object in the image to the actual size of the object in real life *hint - ______ factor

Answer 22

magnification factor

Question 23

degree to which an image is larger than the actual object = _________

Answer 23

magnification factor

Question 24

due to what is why an image is always larger than the actual object for xrays -

Answer 24

beam divergence

Question 25

magnification factor can be effected by what? (2)

Answer 25

xray source to image receptor distance -
and object to be imaged distance to image receptor

Question 26

_______ = the thickness of an absorber required to attenuate the intensity of the beam to half its original value

Answer 26

HVL (half value layer)

Question 27

after a 100% beam comes in contact with a HVL absorber, what will be the intensity after? what if you add another HVL?

Answer 27

50% –> 100/2
if another HVL is added then do 50/2 to get 25%

Question 28

for blocks - transmission rate must be less than what?

Answer 28

5%

Question 29

_______ is used to help calculate for primary barriers

Answer 29

workload

Question 30

______ shows the beam ON time per week

Answer 30

workload

Question 31

workload shows the beam ON time per month, week, day, or minute ?

Answer 31

per week!

Question 32

workload = the weekly dose delivered at ____ distance from source

Answer 32

1 meter

Question 33

what is workload expressed in?

Answer 33

rad / week at 1 meter

Question 34

you DO or DO NOT square the fields before plugging them into Blocked Equivalent Square calculation?

Answer 34

do not!

Question 35

what is fun way to remember conversions?

Answer 35

KHDBDCM -
King Henry Died By Drinking Choco Milk