Math formulas

Question 1

what is the inverse square formula? I1-D2 - 2

Answer 1

(I1/I2) = (D2/D1)^2

Question 2

what’s the formula to see if its underused or overdosed? ( 2 slices )

Answer 2

(ssd1/ssd2)^2

Question 3

what the direct proportions formula? ( F shelly)

Answer 3

(FS1/FS2) = (SSD1/SSd2)

Question 4

what’s the central axis formula? (find doses besides PDD) no cross dressing for A and B

Answer 4

DoseA/ DepthA = Dose B/ Depth B

Question 5

What is the formula for PDD? ( max is under 100 ft below the the deck

Answer 5

PDD = (Absorbed dose at depth/Aboserbed dose at dmax) x 100

Question 6

what is the Maynor F formula? no max on deck

Answer 6

Maynor F = ( ssd(new) + dmax)/(Ssd(old)+dmax) x (Ssd(old) + depth / Ssd(new) + depth ) x 2

Question 7

What is the formula for new PDD

Answer 7

New PDD = Maynor F x old PDD

Question 8

what is the magnification factor? I then O

Answer 8

Image Size/ Object size or SID/SOD

SID - Source to image distance
SOD - source to object distance

Question 9

what is the formula for Dose at DMax(applied dose)

Answer 9

Total dose / PDD

Question 10

what is the formula for dose at a depth?

Answer 10

Applied dose x pDD of depth

Question 11

what is the Gap formula?

Answer 11

gap call = d/2 (L1/ssd1. + l2/ssd2)

Question 12

what is the collimator rotation for CSI? (Spine) broke in half by the sun

Answer 12

Arc tan x 1/2 (L1/ssd1)

L1 = length of spine

Ssd = Spine

Question 13

what is the couch rotation for CSI? (Brain) - brain broke in half cause he fell from the couch

Answer 13

Arc tan x 1/2(L2/SAdD)

L2 = length of brain field

SAD = BrAin

Question 14

what is the equivalent square?

Answer 14

ES = 2(AxB)/ (A+B)

B - perimeter

Question 15

what is blocked area Formula?

Answer 15

BS = square root (area of open field) - (area of blocked field)

Question 16

what is the field weighing/ Mu weighing formula?

Answer 16

Field weighing/MU = total dose/mu x Weight of field/sum of field

Question 17

what is the gantry speed formulas?

Answer 17

gantry speed = degrees of arc / MU

Question 18

what is the therapeutic ratio formula

Answer 18

Therapeutic ratio = normal tissue tolerance/ tumor metal dose

if answer is less than 1 then no its not favorable therapeutic ratio

Question 19

what is the tissue weighting formula? ME U weight of F / Sum of F

Answer 19

MU x (weight of field/ sum of field)

Question 20

What is the wedge angle?

Answer 20

Wedge angle = 90 - Hinge angle/2

wedge angle - angle of the actual wedge angle

Question 21

what is the hinge angle ?

Answer 21

Hinge angle = 180 - (Wedge angle x2)

• angle between gantry angles

Question 22

What is the HVL formula?

Answer 22

.693/M. - ??

m - coefficient

Question 23

what is the temperature correct formula ?

Answer 23

(f + 273)/295 x (760/p)

Question 24

temperature change F to celcius

Answer 24

TC = (Tf -32) x (5/9)

Question 25

what are the MU calculations? SSD

Answer 25

Dose/ PDD x everything else

Question 26

what is the wedge factor formula? beam shaping

Answer 26

dose With wedge factor / dose with out wedge factor

Question 27

what is the Oxygen formula?

Answer 27

OER = Oxgen with O / Oxygen with o

Question 27

What are the MU cal for SAD

Answer 27

SAD = dose/ TAR x everything else

Question 28

What is the Extende distance (Inver square formula?

Answer 28

ISF = (Calibrated Ssd + depth / Extended SSD + depth) ^2

Question 29

what is the Work load factor formula?

Answer 29

Work load = number of patients x dose at 1m per week

Question 30

What is the electrons line 80% inside line formula?

Answer 30

80% inside line = Mev/3

Question 31

what is the electron line at 90% Line formula?

Answer 31

90% isode line = Mev/4

Question 32

what is the useful range formula ?

Answer 32

Useful range = Mev/2

Question 33

Electron cutout thickness in mm

Answer 33

(MeV/2 ) + 1

Question 34

what is the activity formula

Answer 34

AF = Ao(.5) ^ t/ T1/2

Question 35

what is the half life formula

Answer 35

.693/l

Question 36

what is the mean life formula?

Answer 36

1.44 x (T 1/2)