Ch. 31 Computed Radiography Flashcards
PSL
Photostimulable Luminescence
PSP
Photostimulable Phosphor
SPS
Storage Phosphor Screen
IP
Imaging Plate
SP
Storage Phosphor
PMT
Photomultiplier Tube
PD
Photodiode
Computed Radiography was developed in the early 80s by?
Fuji
What are the 5 layers of the PSP plate?
- Protective Layer
- Phosphor Layer
- Support Layer
- Conductor Layer
- Light Shielding Layer
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What are the 2 types of phosphor layers and which one is more effective?
Conventional Powder PSP and Needle PSP.
Needle PSP is better
X-ray interaction with a photostimulable phosphor results in excitation of electrons into what state?
Metastable State
When metastable electrons return to their ground state this is emitted.
Visible Light
When fluorohalides luminesce they do not release all the energy absorbed in the incident beam. Some light is emitted with the interaction, but the phosphor retains energy in the form of what?
Latent Image
The latent image is created by energy transfers during what interactions?
Photoelectric
Photoelectrons produced, excite low energy electrons to create holes in the crystal phosphor these holes are what?
The latent image
Trapped signal will occur exponentially overtime through spontaneous phosphorescence, this is called?
Fading
A typical imaging plate will lost about ____ of the stored signal between 10 minutes to 8 hours after an exposure and more slowly afterwards.
25%
A computed Radiography Reader is comprised of what modules?
Mechanical, optical and computer modules.
What are the 2 main mechanical features of the CR?
- Drive Mechanism
2. Oscillating Mirror
This is a mechanical feature of CR readers that moves the IP along the long axis of the plate and is a slow scan.
Drive mechanism
This is a mechanical feature of CR readers that deflects the laser back and forth across the IP and is a fast scan.
Oscillating Mirror
After the imaging plate has been inserted into the cassette reader it is opened and the imaging plate is removed and advanced between the roller drive system. A laser beam that has been directed through a focusing lens scans the plate in a raster pattern. When the laser strikes the surface of the plate, light is emitted and channeled up to the Photo Multiplier tube. The PMT sends the analog signal to the analog to digital convertor ADC , which sends the digital signal to the computer for processing and display. This is what process?
Readout Process
What is a raster pattern?
A scan of horizontal scanning lines traced by the electron beam. Scans reading across back and forth line by line.
What are the 5 optical features of CR reader?
- Laser
- Beam Shaping Optics
- Light Collecting Optics
- Optical Filters
- Photodetector