crdr 4 Flashcards
he reported a clever approach to describing and identifying the various DR imaging systems
ehsan samei
x-ray is captured
capture element
capture element
- sodium iodide (NaI)
- cesium iodide (CsI)
- gadolinium oxysulfide (GdOS)
- amorphous selenium (a-Se)
transfers the x-ray–generated signal to the collection element
coupling element
coupling element
lens/fiberoptic assembly
contact layer
amorphous selenium
may be a photodiode, CCD, TFT
collection element
developed by CT vendors to facilitate patient positioning
scanned projection radiography (SPR)
obtained in computed tomography by maintaining the energized x- ray tube–detector array fixed while the patient is translated through the gantry
SPR
when was SPR developed
during 1980s and early 1990s
in SPR, X-ray tube and detector array do not rotate but are stationary
SPR was developed for
dedicated chest DR
principal advantage of SPR
- collimation to a fan x-ray with associated scatter radiation rejection and
- improvement in image contrast
2 collimators in SPR
pre-patient collimator
post-patient collimator
x-ray bean is collimated to a fan by
pre-patient collimator
image-forming x- rays likewise are collimated to a fan that corresponds to the detector array
post-patient collimator
scintillation phosphor in SPR
NaI (sodium iodide)
CsI (cesium iodide)
scintillation phosphor is married to linear array of CCDs through a
fiberoptic light path
purpose of all forms of tomography and the goal of DRT is to
improve image contrast
when was CCD developed
1970s
3 principal advantageous imaging characteristics of CCD
sensitivity
dynamic range
size
CCD is a silicon-based semiconductor
ability of the CCD to detect and respond to very low levels of visible light
sensitivity
ability of the CCD to respond to a wide range of light intensity, from very dim to very bright
dynamic range
size of CCD
1-2 cm
