A novel flat-panel imager for medical x-rays

A device that combines an avalanche-mode amorphous selenium pho-toconductor with a field-emitter-array readout could provide high-resolution x-ray images at low doses. The last decade has seen rapid development and clinical adop-tion of active-matrix flat-panel imagers (AMFPIs) for diagnostic x-ray imaging. AMFPIs provide better image quality than tra-ditional screen films and computed radiography,1, 2 but further improvement is desirable, especially in spatial resolution and low-dose performance. Existing AMFPIs use a two-dimensional array of thin-film transistors to read out a charge image gener-ated by an x-ray image sensor. In ‘direct conversion ’ this sen-sor is an x-ray photoconductor, while in ‘indirect conversion ’ the sensor is a scintillator coupled with discrete photodiodes. These methods have two main limitations. First, in low-dose applica-tions such as fluoroscopy (real-time x-ray imaging), electroni