Rad Phys exam 2 Spring 2015 Flashcards
When the image on a film is very grey but the density is good, it is said to be?
low contrast
Which technique would give the longest scale of CONTRAST?
110kV at 7.5 mAs
The term “optimal kV” refers to?
the lowest possible mAs with acceptable contrast on the film
What would the results be if you increased the kV to accomplish a doubling of the film density and cut the mAs in half?
the film density would remain the same and the contrast would decrease
What is undesirable with magnification distortion?
the borders of the object will be blurred
Which would double the number of photons?
going from a 100 mA station to a 200mA station
How would an image appear if there was patient motion during exposure?
blurry
What is true about x-ray beam?
exposure to it will cause x-ray film to darken, the greater its intensity the more penetrating it is, its intensity lessens as the distance increases from the source
If you saw blood vessels on end (axillary) on a chest film, it would probably look like which four natural body densities?
metal
Back scatter is most closely related to?
scatter that has been directed toward the tube
Which of the following is true about increasing kV?
it will increase scatter from the patient
the rays that exit the patient and hit the film are termed?
remnant rays
Which would have the longest scale of CONTRAST?
5 mAs and 100 kVp
If you wanted to increase contrast and maintain the same density of a previously taken film, what would you do?
double the mAs and decrease the kV by 15%
Which is the recommended optimal kV range for lateral thoracic and lumbar?
85-95kV
Recommended optimal kV range for cervical spine, AP thoracic and pelvis/hip?
75-85kV
optimal kV range for AP lumbar?
80-90kV
optimal kV range for AP full spine?
80-100kV
mAs primarily influences which of the following? kV?
density…kV-contrast “kontrast”
to decrease density of a previously taken film by 1/2, what would you do?
decrease mAs by 50%
uses air gap technique?
lateral cervical
which is preferred for spinal filming?
a fixed kV technique
when using air gap technique, what is not needed?
grid
preferred ratio for spinal filming?
10:1
back scatter is most closely related to?
scatter that has been directed toward the tube
what is the most common type of scatter radiation we will produce in our x-ray facility?
compton’s
what would the results be if you increased kV to accomplish a doubling of the film density and cut the mAs in half?
the film density would remain the same and contrast would decrease
what is the term used when comparing the height of the absorbing strips to the width of the interspacing material of a grid?
grid ratio
if you took a 14” x 17” film of a patients body part and then you wanted to take an 8” x 10” film of the same area with the central ray, kV and mAs the same and both collimated to size, what would you expect the outcome to be?
the 8 x 10 would be lighter than the 14 x 17
if a film is too dark it is said to be?
overexposed
when x-raying an elderly obese patient, what would be helpful in obtaining the best quality film?
using a lower kV in the optimal range
if you compared two radiographs of a cervical spine with one having been taken at 40” and the other at 72” with the appropriate change in the radiographic technique, what would you find?
om the 72” film the image would be smaller and clearer
if you saw two structures each with paralleling tracks of calcification overlying the articular pillars diverging at the superior closer at the inferior, what would you be looking at?
part of the thyroid cartilage
what will absorb the most x-rays?
bone
when looking at a cervical film you notice that one side is lighter than the other. what should you suspect is the cause of this appearance?
your focused grid has been installed backwards
lateral cervical x-rays are too light but all the structure show up. used 50 kV at 10 mAs at 72” source image distance using a 400 speed screen. what is the best solution?
increase kVp by 15%
what best describes the outcome of reducing the mAs by 1/2 and keeping the kV and distance constant?
the film density would decrease
what would cause a decrease in subject density?
disuse atrophy
what could be a problem if your X-ray tube was laterally shifted from the center of the film?
shape distortion
recommended for the usual chiropractic office use?
a focused grid
the height of a grid lead strips compared to the width between them is called what?
grid ratio
if you wanted to alter your contrast so that a radiograph had more gray tones, what would you increase?
kV
refers to an attenuation of part of the beam by the grid
grid cut off
why is a fixed kV technique preferred?
contrast is consistent
a film that is lighter on one side than the other most likely would indicate?
grid cut off
best describes back scatter?
scatter that is directed toward the tube
