Chapter 4 mosby

aargueta93's version from 2015-10-31 23:19

Factors controlling and influencing density

Question Answer
Define densityamount of blackness on a given area of a radiograph
What controls densitynumber of exit (remnant rays striking the image receptors and window level
mAs controls quantity or qualityquantity
kVp control quantity or qualityquality
what is the purpose of a grid?decrease the amount of scatter radiation striking the image receptor
What decreases on an image unless mAs is increased on a radiograph?density
Define contrastdifference in adjacent densities on a radiograph
High Contrastfew gray of tones, mainly black and white images, may also be referred to as short scale contrast.


Question Answer
Linearlead strips are parallel to one another, Xray tube may be angled along the length of the grid w/o cutoff
What is grid cutoffdecreased density along the periphery of the image caused by absorption of image forming rays.
Focused gridslead strips are angled to coincide with divergence of x-ray beam, are used w/ specific SID
Crossed Gridsalso known as cross hatch grids, consist of two linear grids placed perpendicular to each other, superior scatter cleanup, allow no angulation of xray beam, require perfect positioning and centering

grid errors

Question Answer
upside down gridnormal density in the middle of the radiograph and decreased density on the sides.
off levelresult in image forming xrays being absorbed all across the radiographic field, with cuttoff ( decreased density) visible over the entire radiograph. the grids must be perpendicular to the grids to avoid this.
lateral decenteringcentral ray does not strike the grid in the center, cuttoff visible more to one side of the radiograph
grid focus decenteringciolation of the grid radius when a focused grid is used, normal density in the middle of the radiograph with cutoff visible on the sides

DIGITAL IMAGING CR(computed radiography)

Question Answer
What are IP (imaging plate) made of?photostimulable phosphor (PSP)