Understanding Digital Radiography (DR) vs Computed Radiography (CR)
The fundamental physics and operational architecture of direct flat panels versus photostimulable phosphor plates.
1. How Computed Radiography (CR) Works
In CR, X-ray photons strike a phosphor plate coated with europium-doped barium fluorohalide crystals. Electrons are excited into meta-stable energy traps (F-centers), forming a latent image. The technologist carries the plate to a laser scanner, where a red helium-neon or solid-state laser stimulates the electrons to release blue luminescent light, which is read by a photomultiplier tube.
2. How Digital Radiography (DR) Works
Direct DR flat panels eliminate the laser scanning step entirely. X-rays hit a Cesium Iodide scintillator, creating visible light photons that are detected immediately by an underlying amorphous silicon photodiode array. Each pixel has a dedicated thin-film transistor (TFT) switch that reads out charge row-by-row in milliseconds, displaying the digital image on screen in under 3 seconds.