DR systems Flashcards
what are some advantages of Digital Radiography
wide latitude
ability to window image to exploit this dynamic range
ability to process and store the images on the computer
the thin film transistor array (TFT) is common to both indirect and direct DR systems. True or False
True
what does the detector element consist of?
TFT
charge collection electrode
charge collection capacitor
what connects the TFT and the capacitor
the gate and drain lines connect the TFT and the capacitor
the TFT is ____ during exposure, allowing the charge that is produced to be stored in the ____
the TFT is closed during exposure, allowing the charge that is produced to be stored in the capacitor
when the X-Ray exposure is terminated, one gate line at a time is set to a ___ _____ which activates the ___ along that row
when the x-ray exposure is terminated, one gate line at a time is set to a high voltage which activates the TFTs along that row
charge flows from the ____ to the transistors and down the ____ in parallel
charge flows from the capacitors to the transistors and down the drain lines in parallel
what is the charge met with at the column of each matrix
output charge amplifiers
what effect does deactivating the gate line have?
deactivating the gate line will reset the TFTs for the next exposure
what is the fill factor
the percentage of the detector element that collects the charge from the energy deposited by the photons in the converter material
- basically the area of the detector that can take X-Rays
name some dead areas of the detector
the TFT
the capacitor
the gate and drain connections
what is the effect of a smaller detector element on fill factor and DQE
as detector element gets smaller, the fill factor and DQE gets smaller
what is a typical range for a fill factor
0.5-0.8
what is used as the detector material in direct conversion systems
amorphous selenium
in direct systems, where in relation to the TFT layer is the photoconductor
it is on top of the TFT