# Raphex

## Terms

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- electron energy increases how does surface dose and depth d max change?
- increases, increases
- PE relation to E
- E^-3
- when liquid scintillation counter used?
- beta emitters
- Radiation scattered from patient for safety calcs
- 1,000 x less
- Threshold energy Compton effect
- 30 keV
- 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