computed radiography

computed radiography (CR)

imaging system comprised of photostimulable storage phosphor (PSP) screen, CR reader, and digital electronics

photostimulable storage phosphor (PSP) screen

acquire the x-ray projection image

CR reader

extracts the electronic latent image

digital electronics

converts the analog signals to digital form

screen-film imaging and computed radiography similarities

• use an x-ray sensitive image receptor

• incased un a protective cassette

• can be used interchangeably with any x-ray imaging system

• carry a latent image that must be made visible by processing

screen-film imaging and computed radiography difference

• processing

  • screen-film: image manifested through chemical processing

  • CR: analog image converted into digital signal

photostimulable luminance (PSL)

halide-based phosphors that have energy storage and excitation characteristics

what does photostimulable luminance (PSL) enable phosphors to do?

store x-ray energy temporarily then release the energy upon excitation by a laser beam

what is the photostimulable phosphor (PSP) screen positioned within?

cassette or imaging plate (IP)

what is the commonly used phosphor material in a photostimulable phosphor (PSP) screen?

barium fluorohalide

what are the phosphor particulates in a photostimulable phosphor (PSP) screen bonded with, what does it form, and what is it deposited on?

a cohesive material forming a turbid structure and deposited on a base for mechanical support

what happens to a fraction of energy when the photostimulable phosphor (PSP) screen is exposed to x-rays?

it is stored

where is the imaging plate (IP) inserted and how is it processed after exposure?

inserted into a CR reader and processed by a scanning system/reader

imaging plate (IP) scanning system process steps (5)

1. extracts the PSP screen from the cassette

2. moves the screen across a high intensity scanning laser beam

3. blue-violet light is emitted via photostimulable luminescence (PSL)

4. light energy/signal is intensified by a photomultiplier tube

5. analog signal is changed into an electric/signal signal by an analog to digital converter

what is the analog signal converted to a digital format for?

manipulation, enhancement, viewing, and printing

what is the PSP screen erased by and where is it reloaded into?

erased by a bright light inside the reader and reloaded into the cassette

how long does the CR imaging processing take?

20 seconds

how could the imaging plate be re-used?

a high intensity white light dumps all the remaining energy trapped

CR additional equipment (8)

• CR reader

• imaging plates & cassettes

• QC workstation

• diagnostic workstation/viewer

• laser printer

• archive server

• web server

• film digitizer

what does a CR reader replace?

darkroom, processor, and chemicals

what does a diagnostic viewer replace?

film, storage, and view boxes