Formulas Flashcards
1
Q
Wavelength in formula with speed of light
A
- c=w * f
- c=wavelength x freq
2
Q
work unit
A
J
3
Q
kinetic E formula
A
(1/2)(mass) * velocity^2
4
Q
energy formula
A
E=mc^2
5
Q
E in ev
A
1.24 x 10^-6/wavelength
6
Q
E in kev
A
1.24 x 10^-9/wavelength
7
Q
E in mev
A
1.24 x 10^-12/wavelength
8
Q
transmission intensity formula
A
I/I0–> final intensity/initial intensity
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
10
Q
HC (homogeneity coefficient) formula
A
1st HVL/2nd HVL
11
Q
exposure formula
A
exposure rate * time
12
Q
X= Q/m (units stand for)
A
- X= exposure
- Q= charge
- m= mass
13
Q
1R= ? C/kg
A
2.58 x 10^-4 C/kg air
14
Q
1R= ? rad
A
0.876 rad in air
15
Q
1 rad=? R
A
1.15 R
16
Q
1 rem= ? rad
A
1 rad
17
Q
1 rem= ? Sv
A
0.01Sv
18
Q
100 rem= ? Sv
A
1 Sv
19
Q
1 rad= ? erg/g
A
100 ergs/g
20
Q
1 rad=J/kg
A
10^-2 J/kg
21
Q
100 rad= ? Gy
A
1 Gy
22
Q
1 rad= ? cGy
A
1 cGy
23
Q
1 rad = ? Gy
A
0.01 Gy
24
Q
0.876 rad = ? R
A
1 R
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