3 Flashcards
when using a stationary grid what is recommended for spinal filming
10:1 grid ratio
contrast bt structures of different subject densities is due to what?
differential absorption
which would have the lowest contrast
50 mAs with 110 kV
effect that scatter radiation has on a film
causes graying of the film
with all equal factors which technique would demo the most film grain (quantum mottle)
100 kV with 200 mA for 1/8 sec
the film ____ is the main function of mAs
density
a pt xray is so light you cannot see any bones at all, what change in technique should you do?
double mAs and increase kV by 15% more
pt with the ___ measurements for the AP view will have the grayest AP lumbar film
smallest (rutherford H, meas 20 cm)
to obtain a quality film for an obese pt xray, what should you do
lower kV in the optimal range
osteoporosis will usually require you to:
reduce the tube output
which rad projections routinely uses an air gap technique
lateral cervical
also flexion, extension, and oblique cervical
a film w/ a darkened overall gray appearance could be caused by:
exposure of the film to scatter
grid ____ refers to an attenuation of part of the beam by the grid
cut off
a film that is lighter on one side than the other most likely would indicate:
grid cut off
if you reduce the mAs by one half and keep the kV and distance constant, what is the outcome
the film density would be decreased
what would increase the amount of xrays passing thru the pt w/o an interaction that would prod secondary radiation?
higher kV
what three rad projections should routinely use compensating filtration
AP thoracic
lat thoracic
full spine
comparing 2 films with the kV and mAs constant, one taken at 40” FFD and the other at 72” what would occur
increased density of 40” film
decreased image size on 72” film
what is the 10 day rule
10 days after the onset of menses is the safest time to xray a female
an accurate collimator shouldnt allow more than __% of the SID of light outside the exposure filed
2
-if a film was taken at 80 kV and 100 mA for 1/2 sec
-then a second at 80 kV and 50 mA for 1 sec
-and a third at 80 kV and 200 mA for 1/4 sec
what would the outcome be?
they are all the same
what is most effective in reducing SECONDARY radiation
filtration
too high a kV will have what effect on the film
quantum mottle (grainy)
__% of the mAs is equal to __% of the kV
50%
15%
what step should you take when xraying an elderly female (same as osteoporotic, bedridden)
decrease mAs by 30-50%
rays that exit the pt and hit the film
remnant rays
a lat cervical film could use what that a lat thoracic or lumbar couldnt
air gap
how should you reduce reproductive radiation on a 14 yo female pt with scoliosis of TS and LS
full spine film with pt facing film
72 yo pt gets xrays, what structure has absorbed the most xrays?
mildly osteoporotic pelvis
take a lat lumbar w/ 90 kV at 100 mA for 1/4 sec using 40” FFD, was too light but could see all the structures, what would you do?
increase mA by doubling it
took lat cervical with 66 kV at 100 mA for 1/10 sec at 72” FFD, too light but could see struct, what would you do?
increase kV by 15%
what is most closely related to “differential absorption”?
subject contrast
If a film was taken at 80 kV at 100 mA for ½ second and a second was taken at 80 kV at 50 mA for one second and a third film at 80 kV at 200 mA for ¼ second, what would be the outcome
they would all be the same
