Introduction
Direct Versus Indirect Conversion
- Direct-readout electronic x-ray detectors use either a direct technique or an indirect technique for converting x-ray into an electric charge. In both direct and indirect conversion detectors, the electrical charge patterns that remain after x-ray exposure is sensed by an electronic readout mechanism and analog-to-digital conversion is performed to produce the digital image.
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| Figure 1 : Direct-readout electronic x-ray detectors use either a direct technique or an indirect technique for converting x-rays into an electric charge. Direct-conversion detectors have an x-ray photoconductor, such as amorphous selenium, that converts x-ray photon into an electric charge directly, with no intermediate stage. Indirect-conversion devices have a scintillator that first converts x rays into visible light. The light is then converted into an electric charge by using an amorphous silicon photodiode array or a CCD. Thin-film transistor (TFT) arrays may be used in both direct- and indirect-conversion detectors. |
