Table 2.2 shows the differences among detector technology concerning three
components of digital detectors [14]: the capture element, the coupling element,
and the charge readout element.
CR technology uses an indirect conversion process using a two-stage technique.
X-rays are captured at a storage-phosphor screen (SPS) (e.g.: BaFBr:Eu2+) and then
a photodetector captures the light emitted from the SPS and converts the captured
luminescence into a corresponding digital image.
DR detectors can use either a direct or an indirect process for converting X-rays
into electric charges. These detectors use direct-readout by means of a TFT array
despite the conversion process of the X-ray beam. Direct-conversion detectors have
an X-ray photoconductor—such as amorphous selenium (a-Se)—that converts
directly at only one stage X-ray photons into electric charges.
Indirect-conversion systems use a two-stage technique for conversion. They have
a scintillator, such as cesium iodide (CsI) that converts X-rays into visible light at a
first stage. That light is then converted—at a second stage—into an electric charge
by means of an amorphous silicon photodiode array [15].
Despite the process of X-ray detection and readout digital detectors offer several
advantages when compared to SF systems. These include wide dynamic range,
adjustable image processing, better image quality, rapid image acquisition, and
image access at remote locations [16]