The Multi-Stage Workflow of Image Acquisition, Extraction, and Digitization
The operational cycle of a Computed Radiography system is divided into four critical stages: Exposure, Stimulated Readout, Digitization, and Erasure.
Exposure: The patient is positioned, and the CR cassette is irradiated. The PSP plate captures the latent image.
Stimulated Readout: The technician inserts the cassette into a CR reader (digitizer). Inside, a high-intensity red laser beam (typically 680 nm) scans the plate in a raster pattern. This laser provides the necessary energy to "kick" the trapped electrons out of their traps.
Digitization: As the electrons return to a lower energy state, they release their stored energy as blue-violet light (approx. 400 nm). This light is collected by a light guide and directed to a Photomultiplier Tube (PMT) or a Charge-Coupled Device (CCD). These sensors convert the light into an analog electrical signal, which is then sent to an Analog-to-Digital Converter (ADC) to be mapped onto a pixel matrix.
Erasure: Because the laser readout only releases about 50% of the trapped energy, the plate must be "reset." The reader exposes the plate to an intense white light source to clear any residual electrons, making the plate ready for thousands of subsequent reuses.