Bushong DR questions
describe some applications for the use of a charge coupled device (CCD) in addition to medical imaging.
digital cameras and astrological observations.
How does pixel size in CCD digital radiography compare with that in other forms of DR?
CCD has smaller pixels
What is the principle advantage of scanned projection radiography over tiled CCDs for use in digital radiography?
SPR does not require that static images be fitted together
what are the respective atomic numbers for the xray capture elements of the various digital radiography systems?
Cesium: 55
Iodine: 53
gadolinium: 64
oxygen:8
sulfur: 16
selenium: 34
What are 2 principle phosphors used in digital radiography?
1. cesium iodide (SCI)
2. gadolimium oxysulfide (GdOS)
Why is the fill factor important?
smaller the pixel size, the less the fill factor. lower fill factor requires increased dose
What is the meaning of sensitivity in digital radiography?
how low an xray intensity can be detected
What are the consequences for producing a flat panel digital image receptors with smaller pixels?
What is the importance of an A/D converter in digital radiography?
needed to digitize the converted analog signal.
How is the tiled CCD mosaic made to appear as a single image?
at the end of each CCD by interpolation of pixel values at each tile interface.
describe the role of an active matrix array (AMA) thin film transistor (TFT) assembly?
It is an image receptor for DR
What is meant by "limited spatial resolution"?
limited spatial resolution expressed in lp/mm
By what four methods can a digital radiograph be produced?
1. Charged coupled device
2. cesium iodide married to amorphous selenium
3. gadolinium oxysulfide married to amorphous selenium
4. amorphous selenium.
How does the image line spread function change for the four types of DR?
still under investigation. amorphous selenium should provide best spatial resolution
Two conducting leads are present for each digital pixel. what are they and what do they do?
1.address drive: ID's pixels, causes them to release electric charge.
2. Data line: conducts signal to DAS.
What are the capture, coupling, and collection stages for a a-Se- based DR?
1.capture: selenium
2.coupling: selenium
3. collection: thin film transistor.
How is scanned projection radiography still used in medical imaging?
generalized method of creating a digital image, this is CT
What properties make GdOS a good digital radiography image receptor?
higher DQE
What is the use of TFT, thin film transistor, in digital radiography?
used in direct and indirect capture as a base for the image receptor.