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dosimetry > Formulas > Flashcards

Formulas Flashcards

1
Q

Wavelength in formula with speed of light

A
  • c=w * f

- c=wavelength x freq

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2
Q

work unit

A

J

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3
Q

kinetic E formula

A

(1/2)(mass) * velocity^2

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4
Q

energy formula

A

E=mc^2

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5
Q

E in ev

A

1.24 x 10^-6/wavelength

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6
Q

E in kev

A

1.24 x 10^-9/wavelength

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7
Q

E in mev

A

1.24 x 10^-12/wavelength

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8
Q

transmission intensity formula

A

I/I0–> final intensity/initial intensity

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9
Q

transmission lin atten coef

A
  • I- I0e^-ux –> I0e^-.693x/HVL
  • I= intensity after passing thru filter
  • I0=inten b4 passing thru filter (100)
  • x= thickness of filter
  • u=lin atten coef
  • e= inverse nat log
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10
Q

HC (homogeneity coefficient) formula

A

1st HVL/2nd HVL

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11
Q

exposure formula

A

exposure rate * time

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12
Q

X= Q/m (units stand for)

A
  • X= exposure
  • Q= charge
  • m= mass
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13
Q

1R= ? C/kg

A

2.58 x 10^-4 C/kg air

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14
Q

1R= ? rad

A

0.876 rad in air

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15
Q

1 rad=? R

A

1.15 R

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16
Q

1 rem= ? rad

A

1 rad

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17
Q

1 rem= ? Sv

A

0.01Sv

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18
Q

100 rem= ? Sv

A

1 Sv

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19
Q

1 rad= ? erg/g

A

100 ergs/g

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20
Q

1 rad=J/kg

A

10^-2 J/kg

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21
Q

100 rad= ? Gy

A

1 Gy

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22
Q

1 rad= ? cGy

A

1 cGy

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23
Q

1 rad = ? Gy

A

0.01 Gy

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24
Q

0.876 rad = ? R

A

1 R

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25
Q

1 Gy =? J/kg

A

1 J/kg

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26
Q

1 Gy = ? rad

A

100 rad

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27
Q

1 Gy=? Sv/QF

A

1 Sv/QF

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28
Q

absorbed dose in air formula

A

exposure in R * 0.876 rad/R

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29
Q

absorbed dose in medium formula

A

exposure in R * f-med factor

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30
Q

dose equivalent formula

A

absorbed dose * QF

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31
Q

answer in rem if question in ?

A

rad

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32
Q

answer in Sv if question in ?

A

Gy

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33
Q

geometric penumbra formula

A
  • SS * [(SSD + depth)- SDD)]/SDD

- ex: SS= 2.5 cm, SSD= 78cm, d= 5 cm, SDD= 40 (if no d assume 0)—> 2.5 * [(78+5)-40]/40

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34
Q

fs directly prop to

A

distance

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35
Q

mag factor formula (field size)

A

fs on film/fs @ coll

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36
Q

mag factor formula (object size)

A

size of object on image or film/actual size of object

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37
Q

mag factor formula (distance)

A

source to film distance or source to image distance/source to object distance

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38
Q

abutting flds (gap calc)

A
  • depth/2 * L1/SSD1 + L2/SSD2)

- SAD if fs defined @ SAD

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39
Q

over or underdose formula with distance

A
  • (correct SSD/incorrect SSD)^2
  • ex: 90cGy Rx @ 92cm SSD mistake s/u @ 95 SSD–> (92/95)^2= 0.94= 94%= 6% underdose (further away or bigger #= underdose)
  • what was dose delivered as result? 90 cGy * 0.94= 84.6cGy
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40
Q

Celsius=

A

5/9 (F-32)

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41
Q

Fahrenheit=

A

9/5 C + 32

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42
Q

e- R100=

A

depth @ Dmax

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43
Q

e- R90 =

A
  • 90% isodose

- MeV/4

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44
Q

e- R80 =

A
  • 80% isodose

- D or R80= MeV/3

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45
Q

e- R50 =

A

depth at which dose is 50% of maximum

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46
Q

e- Rp =

A
  • practical range

- E (MeV)/2 or 1/2 nominal E

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47
Q

average E e-

A

depth of R50 x 2.33

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48
Q

MU calc for e- beam

A
  • MU= Rx dose/depth dose * mach calib factor * fs corr factor (cCAL)
  • if depth dose is %- use decimal
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49
Q

beam atten formula

A

dose with device/dose without device

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50
Q

mean life

A

tavg = 1 / λ = 1.44 * t1/2

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51
Q

exposure rate for change in distance

A

X(d)= gamma factor * A/d^2 (cm)

52
Q

OER (oxygen enhanced ratio)

A

absence of O2/presence of O2

53
Q

1 AMU = ? kg

A

1.66 x 10^-27 kg

54
Q

E equiv of 1 AMU=

A

931 MeV

55
Q

Planck’s constant (h)

A
  • 6.62 x 10^-34 J-sec

- E= hv (v=velocity)

56
Q

Avogadro’s #

A

6.0228 x 10^23

57
Q

TMR=

A

TAR/BSF

58
Q

activity formula

A

A = A0 * e-λt

59
Q

SMR=

A

TMR-TMR(0x0)

60
Q

SAR=

A

TAR-TAR(0x0)

61
Q

%DD=

A
  • TAR/BSF * (SSD+Dmax/SSD + d)^2 * 100

- absorbed dose at any depth in phantom div by dose at depth of max dose

62
Q

dose rate @ point =

A

exposure rate constant * f-med * activity * 1/r

63
Q

exposure (x)=

A

X = Γ * Α / d2

64
Q

mean free path formula

A

I/u (u=lin atten coef)

65
Q

uncertainty formula

A

square root of sum (error)^2

66
Q

1/Te=

A
  • 1/Tp + 1/Tb (calc eff T1/2 from physical & biolog T1/2

- if Tp is much smaller than Tb, Teff= Tp

67
Q

iso shift=

A

PDD2= PDD * (SSD + dmax/SSD + d + dmax)^2

68
Q

equivalent square for blocked field formula

A

equiv square open * square root of unblocked

69
Q

dose correction=

A

Do (TAReff/TARphy)

70
Q

given dose

A
  • tumor dose/PDD * 100

- aka dose @ dmax, applied dose, entrance dose, peak absorbed dose

71
Q

back scatter factor (BSF) formula

A
  • dose @ dmax in phantom/dose without backscatter (free space)
  • aka peak scatter factor
  • BSF= TAR at Dmax
72
Q

output calc formula

A

Cfs * Ccal (SSD1 + dmax/SSD2 + dmax)^2

73
Q

equiv square fld formula

A

2 (L*W)/L+W or 4 (area/perimeter)

74
Q

TAR formula

A

dose at a given point in medium/dose at same point in air

75
Q

TMR formula

A

dose @ depth/dose @ dmax

76
Q

TPR formula

A

dose at specified point in tissue/dose at same distance at ref depth in phantom (usu 5 cm)

77
Q

mayneord’s factor formula

A

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

78
Q

new PDD

A

PDD1 * mayneord factor

79
Q

dose rate formula

A

mach output (Ccal) * fmed * BSF

80
Q

beam on time formula

A

dose per fx/dose rate

81
Q

time setting formula

A

beam on time (min) + timer error

82
Q

wedge angle formula

A

90 deg - (hinge angle/2)

83
Q

hinge angle formula

A

180 deg - (2 * wedge angle)

84
Q

ISCF for PDD formula

A

[(ref SSD + depth of dmax)/(tx SSD + depth of dmax)]^2

85
Q

ISCF for TMR formula

A

[(source calib distance)/(SSD + depth)]^2

86
Q

normalization formula

A

new iso line/old iso line * 100

87
Q

weighting formula

A
  • ex: ap, pa , rt, lt 1:1:1.3:1.3 for 180cGy–> 1+1+1.3+1.3= 4.6
  • ap/pa= 180/4.6= 39*1= 39cGy each
  • lt/rt= 180/4.6=39*1.3= 51 cGy each
88
Q

exposure rate for chg in distance

A

X(d)= gamma factor x A/d^2

89
Q

gamma factor unit

A

R * cm^2/mi * hr

90
Q

Sc or output factor

A
  • ratio of output in air for given fs to that of std fld

- most often measured @ SAD

91
Q

evaluation of PDD assumes variation of

A

beam intensity along CAX of beam

92
Q

Sp or phantom scatter factor

A
  • ratio of dose in phantom of a given fs, @ depth of max dose, to dose at same depth, to that of std fs
  • if can accurately measure BSF, Sp is also known as Sp= BSF(r)/BSF(o)
93
Q

TMR concept

A

fractional scatter contribution @ given depth is indep of beam divergence & depends only on field size & depth of overlying tissue for a beam of given E

94
Q

SAR concept

A

-calc scatter dose in medium

95
Q

linear atten coef (u)

A

prob per unit thickness that any 1 photon will be atten

96
Q

mass atten coef

A

u/density

97
Q

equivalent square

A
  • same Pdd & TMR as rect fld

- smaller area than rect fld

98
Q

ESF have same

A

output factor, scatter effects, & DD as rect fld

99
Q

OAR/OCR

A
  • off axis ratio/off center ratio

- ratio of dose at any pt on dose profile/dose at central ray of profile

100
Q

output factors (Sc, Sp)

A

dose rate @ given fld/dose rate of std 10x10 fs

101
Q

beam attenuation formula

A

dose with device/dose without device

102
Q

BSF formula

A
  • dose @ pt @ dmax w/scatter div by dose @ same pt in air w/o scatter
  • dose dmax/dose free air
  • dose on CAX @ dmax/dose in air
103
Q

exposure rate for change in distance

A
  • X(d)= gamma factor x A/d^2
  • A= activity
  • d= distance
  • ex: expos rate @ 5 cm from 10mCi Cs-137–> X= (3.27R x cm^2/mCi x hr) x 10mCi div by 5cm^2= 32.7/25=1.308=1.31 R/hr
104
Q

decay constant

A

0.693/t 1/2

105
Q

cumulative implant dose

A

dose= 1.44 x t1/2 x Do

106
Q

Sc

A

ratio of output in air for given fs to exposure for ref fs

107
Q

inverse square factor

A

(SSD1/SSD2)^2

I1/I2= (d2/d1)^2

108
Q

SMR

A

ratio of scattered dose @ point in phantom to the effective primary dose @ same point @ ref depth of max dose

109
Q

value of c

A

3 x 10^8 m/s OR 3 x 10^10 cm/s

110
Q

force unit

A

Newtons= 1 kg x m/sec^2

111
Q

kinetic E unit

A

J

112
Q

gravitation acceleration unit

A

9.8 m/sec^2

113
Q

potential E unit

A

J

114
Q

1 J = ? kg m^2/sec^2

A

1 kg m^2/sec^2

1 N-m

115
Q

SAR formula

A

scatter @ given pt in med/dose in air @ same pt (w/o scatter)

116
Q

linear atten coef depends on

A
  • nature of material
  • energy
  • Z impacts lin atten coef
117
Q

linear atten coef formula

A

-0.693/HVL

118
Q

mass atten coef depends on

A
  • E of beam

- material

119
Q

mass atten coef independent of

A

density

120
Q

increase E = ? BSF

A

decrease

121
Q

increase field size = ? BSF

A

increase

122
Q

Measure of ionization produced in air by photons, X =

A

dQ/dm

123
Q

Exposure rate

A

A x exp rate constant/ distance^2

124
Q

F factor is

A

0.876 rads/R

125
Q

Z/A for all elements is approx

A

0.5

dosimetry (53 decks)

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