Digital Radiography, more commonly known as Flat Panel Detector (FPD) technology, began its first commercial use in the mid-late 90's. Todays Flat Panel Detector technology can be classified into two main categories: Indirect and Direct capture, Indirect being the most common commercially available FPD technology.
Indirect capture uses an Amorphous-Silicon (a-Si) detector, and requires a scintillator layer to first convert X-ray energy into light, which then is converted into output signal. The two most commonly used scintillator materials being used are Gadolinium-Oxysulfide (GOS) and Cesium-Iodide (CsI).
Indirect - Scintillator Technology:
- Gadolinium-Oxysulfide - provides a better image quality than CR, and is generally lower in cost compared to Cesium-Iodide.
- Cesium-Iodide - provides better image quality and has a lower patient dose requirement than GOS, but costs a bit more.
Direct capture uses an Amorphous-Selenium (a-Se) detector, which does not require a scintillator layer because it converts X-ray energy directly into output signal.
With so many different FPD options on the market, one defining difference between one manufacturer to another is in the all-important Image Processing Algorithms. This is the process that takes the output signal and turns it into an image that makes sense to us. Image processing is a key feature of digital radiography, greatly influencing the way the image appears to the reader. It is possible to test two FPD's from two different manufacturers, both using the identical FPD hardware, yet see image quality differences. Although software products from several manufacturers use similar algorithms such as edge enhancement, noise reduction, and contrast enhancement to alter the appearance of the image, the resulting impressions may differ considerably.