An efficient digital X-ray imaging system with high spatial resolution and robust energy sensitivity

A one-dimensional array of X-ray detection pixels is formed by orienting a silicon strip detector edge on, with its strips parallel to the X-ray beam. Spatial resolution is governed by the pixel size, defined by the silicon thickness and strip pitch. The detector orientation presents a large apparent depth for X-ray conversion, resulting in a high quantum efficiency. Coarse, but very stable X-ray energy determination is made by counting the number of conversions as a function of depth in each pixel: The strips (pixels) are subdivided into segments, each sampling a different conversion interval. Custom CMOS ICs provides each detector element with an independent low noise preamp, shaper, comparator and 16-bit counter. During the acquisition phase, each channel counts X-ray conversions, at rates in the 1 MHz range. Readout consists of uploading the counter sums (8 bytes/pixel) to the host computer.