Digital X-ray machines utilize a combination of digital image processing and X-radiation technologies to generate radiographs. They are equipped with X-ray detectors which replace traditional plastic films to produce digitalized images. Compared with the legacy equipments, digital X-ray machines realize a faster imaging process with better quality, and more importantly, reduce radiation dose that is required for imaging.
Digital X-ray machines commonly use direct or indirect-conversion-based FPDs (Flat Panel Detectors) to detect X rays. A direct-conversion-based FPD, which converts received X rays into electric signals directly, is made up of an amorphous selenium layer and a TFT array. While an indirect-conversion-based FPD is built with an amorphous silicon layer, a photodiode array and a TFT array are used to convert X rays into visible light first with an amorphous silicon layer, and then convert into electric signals with a photodiode array.
A processor is used to control bias voltage imposed on TFT array, and also transmit the charge stored in TFT to a signal acquisition circuit according to a specific sequence by multiplexing. The signal acquisition circuit has an analog front end to convert the charge into voltage and amplify the voltage which represents power level of X-ray. The amplified signal is converted to digital signal by an A/D converter, and then processed by a DSP to create images. These images could be displayed on screen, printed or transmitted to a remote terminal for medical diagnosis.
With the introduction of new materials to FPDs and the development of digital image processing technology, digital X-ray machines with higher resolution and faster and more accurate image reconstruction are set to replace traditional X-ray devices.