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76 Cards in this Set
- Front
- Back
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Ct,p
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273+C/295 x 760/P
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Electrons, formula to find 50% dd
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E/2.33
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Clinical range Electrons
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E/3 - E/4
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max energy of scattered photon at 90deg
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511 keV
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rest energy proton
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938 MeV
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Daily check, QA, gamma knife
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timer, safety checks
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List the KiloV units
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grenz, contact, superficial, ortho
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QA, how often check output for gamma knife?
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monthly
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Convert amu to MeV
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1 amu = 931 MeV
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How far do betas travel in tissue?
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0.5 cm/MeV
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How to calculate change in dose due to pt seperation parallel opposed 6xsw
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remember 3% per cm
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Conv QA for photons is...
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2% or 2mm
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Conv QA for electrons is...
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3%, 3 mm
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Dose under %HVT kidney block
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10 - 20% depending energy, FS
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HVT superficial units
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1 - 8 mm Al
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Range energy ortho
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150 - 500 KvP
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SSD ortho
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50 - 70 cm
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Dose monitoring system in beam path...
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dose rate, integral dose, beam symmetry
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tx distance superficial units SSD
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15 - 20
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What determines beam penumbra?
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source size, secondary coll
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Conv E MeV to wavelength in meters
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1.24/lambda
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Activity per unit mass
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specific activity
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increase eff xray unit
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Voltage, Z
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Supervoltage therapy, energy
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500 - 1000 kV
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energy xrays van der Graff
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2 - 10 MV
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magnifies microwaves in linac
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klystron
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Describe grazing hit Compton effect
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photon goes forward, electron at 90 w 0 E
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Describe direct hit Compton
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Max energy electron, which travels fwd, photon 180
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Max energy Compton photon scattered 180
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.255 MeV
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Max energy Compton photon scattered 90
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0.511 MeV
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max Energy compton photon scattered 0
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energy initial photon
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total KE available for ele positron pair for pair production
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hf - 1.02 MeV
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Annihilation radiation, energy each annihilation photon
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0.511 MeV
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Describe the photons created in annihilation radiation
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Two 0.51 MeV particles scattered in opposite directions
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threshhold kVp for xray tube for Compton effect
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90 kVp
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define stopping power
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rate of kinetic energy loss per unit path length
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Number of elements
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103
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Radioactive thresh hold in Z
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82
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Name the 3 naturally occuring radioactive series
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uranium, actinium, thorium
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define: equilibrium isotopes
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ratio of daughter to parent activity constant
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KE alpha particles
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5 - 10 MeV
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Describe K capture
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Electron capture of electron in orbit closest to nucleus, competes with positron decay
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Define fission
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Bombarding high atomic elements with neutrons
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Describe fusion
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low mass nuclei combined to produce one nucleus
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formula exposure rate
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gamma X activity / ISF
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define apparent activity
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in terms of encapsulated 0.5 mm Pb radium at 1-m
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Gamma factor radium
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8.25 Rcm^2/mCi-hr WATCH UNITS
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converting mCi to mg-Ra equi
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strength = gamma/gamma-Ra x app activity mCi
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radial dose important for which low energy sources?
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I-125, P-103
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Which brachy system implants more dose at periphery?
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PP
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When do you need more radium in Quimby sys than in PP?
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When dose rx at min
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Which system uses long lines sources for implants?
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Paris
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Which implant system calcs rx from basal dose?
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Paris
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What 3 things needed for implants according ICRU?
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ref kerma, dim target, ref pts
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Decay I and Pd
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e capture
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Which nuclides anisotrophy factors?
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I 125, Pd 103
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Energy radium and radon
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800 keV
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rad protection stds for nuclear reactors set by this US body
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NRC
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stds for naturally occuring radionuclides set by this body
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state
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recomm adhered to by states set by this body
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NCRP
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Factor that converts dose to bio effect
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Q
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Negligible risk factor
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0.01 mSv
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occup dose lens
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150 mSv
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formula for exposure from brachy sources for rad safety and barrier Thickness
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X [R] = gamma x activity x time x B / ISF
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Formula to calc # TVLs
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- log (B)
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Formula to calc thickness of wall from TVL
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- TVL log (B)
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If B = 10^-5, how many TVLs?
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5
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5 TVLs of concrete for 6X
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168 cm
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Year R adopted ICRU as unit
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1928
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Year Cobalt 60
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1951
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Si unit X
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C/kg
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Clinical unit X
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r
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Energy limit free air ionization measurements
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3 MeV
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Density of mass in air in thimble chamber increases with...
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decreasing T and increasing P
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TG report measure'ts absorbed dose
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51
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In tx breast, dose at chest-lung interface
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80% or E = depth x 3
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