Treatment Planning Calculations

Question 1

what is equation for hinge angle?

Answer 1

hinge = 180 - (wedge x 2)

Question 2

what is equation for wedge angle?

Answer 2

wedge = 90 - (hinge/2)

Question 3

__heels//heel & toe___ always together

Answer 3

heels always together, and vice versa toes always together

Question 4

_____ angle is the angle between two beam angles

Answer 4

hinge

Question 5

label peach and green -

Answer 5

peach = wedge angles
green = heel angle

Question 6

practice!

1. find WEDGE angle
2. find HINGE angle

Answer 6

1. wedge = 60 degrees
2. hinge = 120 degrees

Question 7

_________ are angles with 90 degrees between them

Answer 7

orthogonals

Question 8

you can say that orthogonals are angles with a 90 degree ___wedge/hinge___ angle between them

Answer 8

hinge

Question 9

practice!
answer the following gantry angle question

“Determine the next gantry angle if given one field for an orthogonal pair”

Answer 9

1. CW (clockwise) angle –> = 155 degrees
2. CCW (counterclockwise) angle –> = 335 degrees

Question 10

what is equation for an open field equivalent square?

Answer 10

2ab / (a+b)

Question 11

for all Dosimetric calculations, all rectangular fields need to be converted to ________

Answer 11

squares

Question 12

what is equation for a BLOCKED field equivalent square?

Answer 12

square root of (open area) - (blocked area)

Question 13

what is area of a square?

Answer 13

length x width

Question 14

practice!
Find equivalent square -

*hint this is a blocked field!

Answer 14

eqsq =
11.2 x 11.2 sq

Question 15

what is equation for Dose per Field?

Answer 15

total dose x (weight of field) / (sum of all field weights)

Question 16

what is equation for MU per Field?

Answer 16

total MU x (weight of field) / (sum of all field weights)

Question 17

T/F: doses from multiple fields are NOT always equal

Answer 17

true

Question 18

if doses are not equal from multiple sources, what is used?

Answer 18

field weighting

Question 19

what are examples of when field weighting would/could be used?

Answer 19

• tumor does not lie at mid-depth
• beam may be going through a critical structure/OAR

Question 20

practice!
answer this field weighting question -

Answer 20

AP = 75 cGy

PA = 225 cGy