Bushong CR
what work load steps were omitted when conversion from screen film radiography to computed radiography was complete?
The necessary reloading of the cassette.
What is the approximate color of stimulating light and emitted light?
Stimulating light: red/orange
Emitted light: blue/green
Why is Beam shaping required for the laser beam?
ensures the laser beam interacts with the imaging plate. remains a circle, not distorted.
how is the latent image made visible in computed radiography?
stimulating the metastable electrons with an intense laser light beam.
Identify 3 photostimulable phosphors.
1. BaFBR:Eu
2.Bafl:Eu
3. Baff:Eu
What is the purpose of an optical filter positioned before the photo detector?
To absorb scatter long wavelength laser light
What are the 3 subsystems of a computed radiography reader?
1.mechanical drive system
2. optical beam shaping/collecting systems
3. computer control system
What is the purpose of europium in a photostimulable phosphor?
It is an activator. traps electrons in a metastable state.
how is the latent image formed in computed radiography?
electrons are energized by Xray interaction with excited metastable energy states, They remain in these excited states until released by exposure to laser light
What is the difference between fast scan and slow scan?
Fast scan: the rapid back and fourth of the laser beam.
Slow scan: the mechanical drive of the imaging plate in through the reader.
How is ghosting caused by residual laten image reduced?
additional erasing in the CR reader.
What are the layer of a CR imaging plate?
1. top (protective overcoat)
2. PSP crystal
3. r100-250 mm of phosphor
4. Reflective layer
5. base
6. antistatic layer
7.bottom (lead)
what causes a photostimulable phosphor to appear turbid?
The small size of crystals, causing them to scatter incident light
What is the difference between an analog signal and a digital signal?
Analog signal: continuous modulation of an electric signal
Digital Signal: Has discrete values that make it more compatible with computer techniques.
What is the approximate difference in wavelength between prompt emission and stimulated emission?
They have the same wavelength.
How do we reduce backscatter radiation in computed radiography?
The imaging plate is backed by lead, which absorbs backscatter radiation. which would increase the background noise on the image.
What is the difference between sampling and quantization?
sampling: how rapidly an analog signal is interrogated.
Quantization: After sample, amplitude of that signal is given a discrete value or quantized.
How should you handle a CR imaging plate?
with the same care given to the screen film cassette.