1 year topics

what is evaluated during a small bowel series?

duodenum, jejunum, illeum

what position demonstrates the hepatic flexure the best?

lpo

what projection shows duodenal bulb and loop in profile the best

rao

what projection is best to see esophogus free of superimposition of spine

rao

what is order of retrograde filling of BE

anus, rectum, sigmoid, descending, transverse, ascending cecum

what are 8 factors that affect receptor exposure

kvp, mas, sid, collimation, patient thickness, tissue density, grids, filtration

inverse square law

intensity is inversely related to the distance squared

as i double my distance from source what happens to intensity

cut into 1/4

does increasing SID decrease or increase receptor exposure

decrease

does increasing filtration increase or decrease receptor exposure

decrease (removes low energy x rays)

if an incoming photons energy is higher than the binding energy of the tissue, what interaction will occur

PE

if the binding energy of a tissue is higher than an incoming photon what interaction will occur

none

ways to remember if photon needs more or less energy

photon needs enough energy to knock out an inner shell electron

if tissues energy is too high, photon wont have enough to knock an electron out

does photoelecteon increase or decrease with high kvp

decrease

what is primary controlling factor of radiographic contrast

kvp

if theres inadequate mas what happens to the image

quantum mottle increases, grainy

what is the controlling factor of spatial resolution

focal spot size

more OID does what to spatial resolution and why

reduces it because could cause magnification

image processing (window level) and receptor exposure affects what

brightness

Low kVp causes high or low subject contrast

High

Low kvp causes short or long scale radiographic contrast

short scale

To double receptor exposure (brightness) what do you do to kvp and mas and why

Increase kvp 15% keep mas same because making the beam stronger means more photons hitting receptor.

What do you do to technique to maintain brightness but lower contrast and why

Increase kvp 15% half MAs

Because throwing half as many photons but throwing them harder

What kind of subject contrast does low kvp have and why

High because it’s not as strong enough to pass through bone so it absorbs causing more contrast

When going from non grid to 5:1 grid increase kvp by

8-10

When going from non grid to 8:1 grid increase kvp by

13-15

When going from non grid to 16:1 grid increase kvp by

30-40

Think of this:

mAs like paint balls; more paint thrown, darker the color

(More x rays thrown, darker the image)

If image is too light after collimating, what do you increase ?

mAs

For overall brightness of an image you want more?

Mas

Receptor exposure