2 Flashcards
what increases compton’s radiation?
higher kVp
term used when comparing the height of the absorbing strips to the width of the interspacing material of a grid
grid ratio
rec optimal kV range for an AP lumbar film
80-90
which interspacing material is best for xraying the spine
aluminum
scatter that is directed toward the tube is known as
back scatter
if you wanted to alter your contrast so that the radiograph had more gray tones, what would you INCREASE
kV
what effect does using a reciprocating grid have that a stationary grid doesnt?
blurs out grid lines
what would produce a film with the most visible grainy?
high kVp / low mAs film
which of the four lateral cervical films would be DARKEST? 75 kV and 14 mAs 65 kV and 14 mAs 85 kV and 14 mAs 95 kV and 14 mAs
the fourth
how much increase in mAs is needed to maintain the same density when reducing the xray frield from 14x17” to 8x10”
60%
T/F: the more peripheral parts of the xray beam cause less distortion
FALSE
recommended optimal kV range for AP full spine
80-100
a film exposed to secondary radiation will have what appearance
it grays the film making it dark
an INCREASE in _____ will most likely DECREASE the amount of scattered radiation to a film
mAs
xraying an elderly obese pt, what would be helpful in obtaining the best quality film?
use a lower kV in the optimal range
what would cause a decrease in SUBJECT density
disuse atrophy
you just receive a 300 mA 125 kV xray unit. the box says “focused grid with focal range of 40-72”, 8:1 ratio, aluminum interspacing material” -why wouldnt you want this?
the max rec kV for an 8:1 grid is 90 and you may want to use more
with variable kV technique and an elderly pt with a 40 cm lumbar region (large abdomen), what is the predictable problem you would have for xray?
there will be too long of a scale of contrast
if you increased the mAs and reduced the kV from a given rad technique what would be the outcome (on the FILM)?
would have more contrast
to decrease density of a previous film by 1/2, which would you do?
decrease mAs by 50%
if a film is too dark, it is AKA
overexposed
rad technique w/ the shortest scale of contrast
60 kV with 100 mA for 2 sec
about how many kV would be needed to make the slightest visible change in density on a radiograph if you were using a SINGLE phase unit
4
what would the effect of adding 100% mAs to a radiographic technique have?
would double the density of the film
what best describes what you should expect if you retake an AP lumbar with 15% decrease in the kV and leave the mAs constant
the density of the film would be reduced by 1/2
rec optimal kV range for an AP thoracic film
75-85
in the port of a used xray tube, the entire surface of the anode has bumps, this is called
anode pitting
a filament does what
forms electrons
in which direction do grid lines run
in the long axis of the pt
which rad technique would cause the most absorption of xrays in a pt BODY
10 mAs with 140 kV (highest kV)
MC cause of a blurry image
pt motion
