Test 2 Flashcards
SID (Source Image Distance) aka
FFD (focal spot film distance)
TFD (target focal distance)
inverse square law
a change in beam intensity varies inversely with the square of the SID
exposure 3 ft from a source is 40 mR/hour; what is exposure rate at 6 ft?
(6^2/ 3^2) * (40/x) or 40*.25 because doubled
= 10 mR/hour
if SID is double, intensity is
1/4 original
if SID is halved, intensity is
4x original
if SID increases, # of x-rays reaching film
decreases
direct square law
old mAs/X = (old SID^2/new SID^2)
if SID doubled, mAs =
4x original
if SID halved, mAs=
1/4 original
classical unit of x-rays in air
Roentgen (R) or mR
classical unit of radiation absorbed dose (patient exposed)
RAD
SI unit for radiation absorbed dose (patient exposed)
Gray (Gy)
___ rad = 1 Gray
100 RAD = 1 Gy
classical unit for radiation equivalent man (occupational exposure)
REM
SI unit for radiation equivalent man (occupational exposure)
Sievert
equation for REM
rad * QF = REM
____ REM = 1 Sievert
100 rem = 1 Sievert
QF for x-ray
1
QF for alpha particles
20
QF for neutrons
5-20 dependent on energy
in x-ray, 1 R = __ RAD = ___ REM
1=1=1
classical unit for quantity of radioactive material
curie
SI unit for quantity of radioactive material
becquerel
important x-ray interactions important for diagnostic level radiography
photoelectric absorption
compton scatter
coherent (not as important)