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Glossary of Raphex

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Created by mrsjande

Threshold energy Compton effect
30 keV
PE relation to E
E^-3
Radiation scattered from patient for safety calcs
1,000 x less
when liquid scintillation counter used?
beta emitters
electron energy increases how does surface dose and depth d max change?
increases, increases
energy 350 kV
Ir 192
more or less scatter for dynamic wedge?
less
More or less MUs w dynamic wedge?
fewer
How does HVL change w increasing energy?
increases, so atten decreases
How far do betas travel in tissue per MeV?
0.5 cm / MeV
Process through which electrons lose energy in tissue.
Ionization and excitation
How does electron ouput change w energy?
decreases
How does electron PDD change w increasing energy?
decreases
What radionuclide emits 27 and 35 keV photons?
I-125
How to calc change dose due to pt seperation parallel opposed 6 Xs
3%/cm
MLC stepping most dramatic at what isodose level
50
Which has sharper fall off from 80 to 20%, low or high energy electrons?
low
which has greater surface dose, low or high energy electrons?
high
Which has broader plateau region, low or high energy electrons?
high
Relationship half life and initial activity
shorter half life higher activity
relationship tx time and initial acitivity
high activity, shorter tx time
relationship half life and tx time
shorter half life shorter tx time
relationship initial dose rate and half life
shorter half life larger initial dose rate
light field/radiation coincidence in mm
2 mm
units f factor
cGy/R
rel TMR TAR
TMR = TAR/BSF
conv amu to MeV
1 amu = 931 MeV
Mega prefix
10^6
ODI tolerance
2 mm
shoulder cell survival curve indicates...
reduced efficiencing killing low dose
giga
10^9
tera
10^12
The maximum number of electrons in the outer shell of an atom is?
8
1 microcurie is equal to _______ Bq?
37,000 Bq
What is the relationship between the linear attenuation coefficient and HVL?
HVL=.693/linear attenuation coefficient
The pair production mass attenuation coefficient is proportional to?
Z
The photoelectric mass attenuation coefficient is proportional to?
Z^3/E^3
What is the relationship between mass att. coeff, linear att coeff, and density?
Mass att coeff = linear att coeff/density
How many TVL in linac head?
Three TVL
What should be used for palliative bone mets?
SR-89
When going from electrons to photons - what is the expected increase in gun current?
1000 times
Given universal wedge (60 deg) w/ wedge factor of 0.5, calculate the ratio of wedged to open fields to give 30 deg eff. wedge?
MU ratio= 2:1

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