Radiation protection Flashcards
how does scatter affect contrast
decrease
- increases photoelectric affect
kvp
source of free electrons
heated filament
thermionic emission
electrons boiling off of heated filament
acceleration of electrons
positive anode, negative cathode kvp= push
deceleration of electrons
hitting anode (kinetic energy to xray)
Bremmstrahlung
electron passes close to the nucleus
nucleus positive makes electrons brake
Most common target interaction
bremmstrahlung
- makes beam hereto
bremmstrahlung
Characteristic
electron gets hit, kicked oput
another electron falls in inner shell
what affects the quantity of Xrays
ma
time
kvp
filtration
what affects quality
kvp
flitration
compton effect aka
modified/incoherent
compton
xray hits an outer electron, some energy absorbed
slightly lower xray goes in diff direction
compton usually happens with
high kvp
most common scatter
compton
photoelectric
xray hits and knocks out electron
electrons fall down to fill hole
most of patient dose happens b/c of
photoelectric
- produces contrast
photoelectric
photoelectric formula
Incoming energy= binding energy + kinetic energy of ejected
coherent scatter aka
unmodified / elastic / rayleigh / classical
coherent
xray hit electron, both vobrate
the electron goes in diff direction
coherent is -% of scatter
3
coherent doesnt happen with kvp lower than
70
differential absorption
ratio of absorption of one tissue to another
partial absorption
how much gets sucked up due to tissue density
- is basis for contrast
partial absorption
thinner part = - attenuation = darker/lighter
less darker
increase tech for - tissue increase
4-5 in
effective dose
absorbed dose x rad weighting factor x tissue type
SV
dose equivalent
absorbed dose x rad weighting factor
harm based on rad type
sv
absorbed dose
energy absorbed
gray
air kerma
the energy of ionization in air
gray
exposure
number of ionizations in the air
columb/kg
linear nonthershold
no level safe
response prop to rad
stotastic dose response
linear nonthershold
linear thershold
low rad= no respose until threshold hit
prop to rad
ARS does response
linear thershold
nonlinear thershold
low rad= no respose until threshold hit
not prop to rad
nonlinear nonthershold
no level can be safe
the response happens at every dose not prop to dose
LET
energy deposited per distance traveled
low LET = - energy = - damage
high, low
RBE
compares rad vs standard
