Dosimetry > Formulas > Flashcards

Formulas Flashcards

(125 cards)

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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
1 Gy =? J/kg
1 J/kg
26
1 Gy = ? rad
100 rad
27
1 Gy=? Sv/QF
1 Sv/QF
28
absorbed dose in air formula
exposure in R * 0.876 rad/R
29
absorbed dose in medium formula
exposure in R * f-med factor
30
dose equivalent formula
absorbed dose * QF
31
answer in rem if question in ?
rad
32
answer in Sv if question in ?
Gy
33
geometric penumbra formula
- 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
34
fs directly prop to
distance
35
mag factor formula (field size)
fs on film/fs @ coll
36
mag factor formula (object size)
size of object on image or film/actual size of object
37
mag factor formula (distance)
source to film distance or source to image distance/source to object distance
38
abutting flds (gap calc)
- depth/2 * L1/SSD1 + L2/SSD2) | - SAD if fs defined @ SAD
39
over or underdose formula with distance
- (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
40
Celsius=
5/9 (F-32)
41
Fahrenheit=
9/5 C + 32
42
e- R100=
depth @ Dmax
43
e- R90 =
- 90% isodose | - MeV/4
44
e- R80 =
- 80% isodose | - D or R80= MeV/3
45
e- R50 =
depth at which dose is 50% of maximum
46
e- Rp =
- practical range | - E (MeV)/2 or 1/2 nominal E
47
average E e-
depth of R50 x 2.33
48
MU calc for e- beam
- MU= Rx dose/depth dose * mach calib factor * fs corr factor (cCAL) - if depth dose is %- use decimal
49
beam atten formula
dose with device/dose without device
50
mean life
tavg = 1 / λ = 1.44 * t1/2
51
exposure rate for change in distance
X(d)= gamma factor * A/d^2 (cm)
52
OER (oxygen enhanced ratio)
absence of O2/presence of O2
53
1 AMU = ? kg
1.66 x 10^-27 kg
54
E equiv of 1 AMU=
931 MeV
55
Planck's constant (h)
- 6.62 x 10^-34 J-sec | - E= hv (v=velocity)
56
Avogadro's #
6.0228 x 10^23
57
TMR=
TAR/BSF
58
activity formula
A = A0 * e-λt
59
SMR=
TMR-TMR(0x0)
60
SAR=
TAR-TAR(0x0)
61
%DD=
- TAR/BSF * (SSD+Dmax/SSD + d)^2 * 100 | - absorbed dose at any depth in phantom div by dose at depth of max dose
62
dose rate @ point =
exposure rate constant * f-med * activity * 1/r
63
exposure (x)=
X = Γ * Α / d2
64
mean free path formula
I/u (u=lin atten coef)
65
uncertainty formula
square root of sum (error)^2
66
1/Te=
- 1/Tp + 1/Tb (calc eff T1/2 from physical & biolog T1/2 | - if Tp is much smaller than Tb, Teff= Tp
67
iso shift=
PDD2= PDD * (SSD + dmax/SSD + d + dmax)^2
68
equivalent square for blocked field formula
equiv square open * square root of unblocked
69
dose correction=
Do (TAReff/TARphy)
70
given dose
- tumor dose/PDD * 100 | - aka dose @ dmax, applied dose, entrance dose, peak absorbed dose
71
back scatter factor (BSF) formula
- dose @ dmax in phantom/dose without backscatter (free space) - aka peak scatter factor - BSF= TAR at Dmax
72
output calc formula
Cfs * Ccal (SSD1 + dmax/SSD2 + dmax)^2
73
equiv square fld formula
2 (L*W)/L+W or 4 (area/perimeter)
74
TAR formula
dose at a given point in medium/dose at same point in air
75
TMR formula
dose @ depth/dose @ dmax
76
TPR formula
dose at specified point in tissue/dose at same distance at ref depth in phantom (usu 5 cm)
77
mayneord's factor formula
(SSD2 + dmax/SSD1 + dmax)^2 x (SSD1 + d/SSD2 + d)^2
78
new PDD
PDD1 * mayneord factor
79
dose rate formula
mach output (Ccal) * fmed * BSF
80
beam on time formula
dose per fx/dose rate
81
time setting formula
beam on time (min) + timer error
82
wedge angle formula
90 deg - (hinge angle/2)
83
hinge angle formula
180 deg - (2 * wedge angle)
84
ISCF for PDD formula
[(ref SSD + depth of dmax)/(tx SSD + depth of dmax)]^2
85
ISCF for TMR formula
[(source calib distance)/(SSD + depth)]^2
86
normalization formula
new iso line/old iso line * 100
87
weighting formula
- 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
exposure rate for chg in distance
X(d)= gamma factor x A/d^2
89
gamma factor unit
R * cm^2/mi * hr
90
Sc or output factor
- ratio of output in air for given fs to that of std fld | - most often measured @ SAD
91
evaluation of PDD assumes variation of
beam intensity along CAX of beam
92
Sp or phantom scatter factor
- 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
TMR concept
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
SAR concept
-calc scatter dose in medium
95
linear atten coef (u)
prob per unit thickness that any 1 photon will be atten
96
mass atten coef
u/density
97
equivalent square
- same Pdd & TMR as rect fld | - smaller area than rect fld
98
ESF have same
output factor, scatter effects, & DD as rect fld
99
OAR/OCR
- off axis ratio/off center ratio | - ratio of dose at any pt on dose profile/dose at central ray of profile
100
output factors (Sc, Sp)
dose rate @ given fld/dose rate of std 10x10 fs
101
beam attenuation formula
dose with device/dose without device
102
BSF formula
- 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
exposure rate for change in distance
- 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
decay constant
0.693/t 1/2
105
cumulative implant dose
dose= 1.44 x t1/2 x Do
106
Sc
ratio of output in air for given fs to exposure for ref fs
107
inverse square factor
(SSD1/SSD2)^2 | I1/I2= (d2/d1)^2
108
SMR
ratio of scattered dose @ point in phantom to the effective primary dose @ same point @ ref depth of max dose
109
value of c
3 x 10^8 m/s OR 3 x 10^10 cm/s
110
force unit
Newtons= 1 kg x m/sec^2
111
kinetic E unit
J
112
gravitation acceleration unit
9.8 m/sec^2
113
potential E unit
J
114
1 J = ? kg m^2/sec^2
1 kg m^2/sec^2 | 1 N-m
115
SAR formula
scatter @ given pt in med/dose in air @ same pt (w/o scatter)
116
linear atten coef depends on
- nature of material - energy - Z impacts lin atten coef
117
linear atten coef formula
-0.693/HVL
118
mass atten coef depends on
- E of beam | - material
119
mass atten coef independent of
density
120
increase E = ? BSF
decrease
121
increase field size = ? BSF
increase
122
Measure of ionization produced in air by photons, X =
dQ/dm
123
Exposure rate
A x exp rate constant/ distance^2
124
F factor is
0.876 rads/R
125
Z/A for all elements is approx
0.5
Dosimetry
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