image production 110820 Flashcards
Quality assurance and maintenance of CR cassettes include cleaning and inspecting the plates at least
every 3 months
Quality assurance and maintenance of CR include erasing the plates at least
every 48 hrs
Quality assurance of digital imaging reqs the uniformity of processing codes to ensure
image appearance consistency
softwiare function that evens the brightness displayed in the image is called
smoothing
smoothing software may result in loss of detail
Beam part receptor alignment latitude describes
the latitude of collimation that still allows the software to detect collimated edges.
Detection of collimated edges is crucial for accurate histogram
In DR inappropriate collimation causes
hisechtogram analysis error
An artificial increase in display contrast act an edge of the image is
edge enhancement
this enhances visibiltiy of detail
If the exposure field is not accurately recognized the histogram will contain data
outside the exposure field, widening the histogram
Digital image receptors are more sensitive to
scatter radiation and background radiaition
Digital imaging is driven by
exposure
“Total Exposure” reaching IR
Digital systems operate at what speed class
the speed class chosen by the radiographer
As speed class increases
The likelihood of noise increases
Increase in KVP and decrease in mAs causes increase in quantum mottle/ or noise
As speed class decreases
Pt exposure increases
More “Total Exposure” reqd to produce useable image
Excessive processing of the digital image may
degrade visibility of anatomy
A high SNR provides an image with
higher spatial reso
Quantum noise limits ability to see
detail
Grid ratio
“The ratio of the HEIGHT of lead strips over the he DISTANCE between the lead strips.
*expressed as H/D
Grid frequency
amount of lead in grid
*expressed number of lead strips per inch
main function of grids
prevent compton scatter fr reaching IR
contrast improvement factor
measure of the grid to enhance contrast
grid selectivity
ratio of primary radiation transmitted thru grid to secondary radiation transmitted thru the grid
lead strips and aluminum interspacers angled to coincide with the divergence of the XR beam is called
focused grid
range of SIDs used with focused grids
grid radius
best scatter clean up is achieved by
crosshatch grids
grid cutoff
decreased density on a radiograph as a result of absorption of image-forming rays
use of airgap
works bc scatter travels in divergent paths and misses IR as a result of increased OID
when using AEC increasing KVP
has no effect on image quality
BC after a certain amount of radiation hits the ionization chambers the exposure terminates
