Formulas

Question 1

PDD is ____/____.

Answer 1

absolute dose at depth/absolute dose at dmax

Question 2

dose along central axis formula/dose at another point when given 2 PDDs and 1 dose:

Answer 2

doseA/PDDA = doseB/PDDB

Question 3

New PDD formula:

Answer 3

Old PPD * MFactor

Question 4

Maynard Factor formula:

Answer 4

(SSD1 + d/SSD1 + dmax)^2 X (SSD2 + dmax/SSD2 + d)^2

Question 5

Mag Factor equations: (3)

Answer 5

SID/SOD

Image size/object size

FFD/FOD

Question 6

Gap formula:

Answer 6

1/2d (L1/SSD1 + L2/SSD2)

Question 7

Equivalent Square formula:

Answer 7

2(l*w)/l+w

Question 8

Blocked Equivalent Square formula:

Answer 8

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

Question 9

If there is a change in SSD when calculating dose or output, use ____.
- Multiply by this or divide?

Answer 9

(what you know/where you wanna go)^2
- Multiply

Question 10

Field weighting - dose per field formula:

Answer 10

total dose * (field weight/total fields)

Question 11

Wedge Factor formula:

Answer 11

dose with wedge/dose without

Question 12

Tray Factor formula:

Answer 12

dose with tray/dose without

Question 13

Gantry Rotation Speed formula:

Answer 13

degress/MUs

Question 14

Radioactivity formulas: (2)
1.
- n =?

Answer 14

1. Afinal = Ainitial (1/2)^n
   - n = t/half life
2. Afinal = Ainitiale^-lamdat

Question 15

Mean Life Formula:

Answer 15

1.44 *T1/2

Question 16

Wedge Angle formula:

Answer 16

90 - (hinge angle/2)

Question 17

Hinge Angle formula:

Answer 17

180 - (wedge angle * 2)

Question 18

Patient Separation is also called: (3)

Answer 18

Pt thickness
Intrafield Distance (IFD)
Innerfield Distance (IFD)

Question 19

Collimator Rotation formula:

Answer 19

tan-1 * 1/2(L1/SSD1)

Question 20

tan-1 * 1/2(L1/SSD1)
- L1 is length of ___ field
- SSD is SSD of ___ field

Answer 20

• Spinal
• Spinal

Question 21

Couch Rotation formula:

Answer 21

tan-1 * 1/2(L2/SAD)

Question 22

tan-1 * 1/2(L2/SAD)
- L2 is length of ___ field
- SAD is SAD of ___ field

Answer 22

• Brain
• Brain

Answer 23

Add image..

Question 24

Use __ (PDD or TMR) for SAD?

Answer 24

TMR

Question 25

Use __ (PDD or TMR) for SSD?

Answer 25

PDD