Unit 3 Computed Radiography (CR)

Question 1

Why is CR considered a 2-step process?

Answer 1

Because you take the Image Plate after taking the x-ray image and put it in the reader

Question 2

Advantages of CR

Answer 2

-Light weight
-Durable
-Various cassette sizes
-Can be used with standard x-ray equipment
-Inexpensive
-NOT white light sensitive

Question 3

CR Disadvantages

Answer 3

-Time and Efficiency
-Higher patient dose
-Extremely sensitive to scatter
-Latent image fades after 8 hours

Question 4

What are cassettes made of?

Answer 4

-Aluminum/Plastic
-Carbon fiber front
-Felt lining
-Microchip to store patient information
-Latches/slider button

Question 5

PSP layers: Protective Layer

Answer 5

Guards against damage from handling

Question 6

PSP layers: Phosphor Layer

Answer 6

-ACTIVE LAYER
-Stores latent image

Question 7

PSP Layers: Conductor Layer

Answer 7

Grounds plate to prevent static and absorbs excess light

Question 8

PSP Layers: Support Layer

Answer 8

Rigid layer on which other components are attached

Question 9

PSP layers: Reflective Layer

Answer 9

Prevents light leakage through the backing, protective backing

Question 10

Scintillator

Answer 10

-A material that exhibits luminescence when excited by ionization
-Barium Fluorohalide luminescence when exposed to x-rays

Question 11

Photodetector

Answer 11

Sensors that convert light into electrical signal

Question 12

Describe the steps in Latent Image formation is the PSP

Answer 12

1. X-rays ionize phosphors and light is emitted during cascade(blue violet light(fluorescence) is released)
2. Freed electrons are trapped by Euphorium F Centers

Question 13

Describe the steps in Latent Image Read out Process

Answer 13

1. Cassette is opened and the PSP is removed mechanically
2. Red laser (red neon helium) is activated, split, focused, and aimed at the Image Plate(IP)
3. Laser scans the IP in a raster pattern
4. Electron releases energy in the form of light (blue violet)
5. The light is captured, multiplied, and converted to electrons in the photomultiplier tube (PMT) —> Photodetector
6. Electrons are sent to the Analog to digital convert the signal to binary code for image processing
7. Bright white light is washed over the IP to clear the residual electrons and erase the IP
8. The IP is then placed back into the cassette and is ready for reuse