The XLV direct conversion detector, presently under development, represents the core technology based on which economic, x-ray detectors will be build for various medical imaging modalities. The first XLV Diagnostics Inc. product will be a full field digital mammography machine providing good quality clinical images for a very low cost to satisfy the upcoming requirements of the $1.4 Billion mammography market.
XLV technology offers a substantial decrease in cost over traditional flat panel detectors by eliminating the need for large area, transistors arrays and expensive, high density, low noise electronics. Instead, a thin liquid crystal layer is positioned between an amorphous Selenium layer and an optical scanner based on consumer electronics technology. The charge image created by x-ray inside Selenium layer is translated by proportional twists of liquid crystals into an optical image that is readable by the optical scanner.
While the XLV principle has been successfully demonstrated, the parametric performance of each sub-system and of the entire detector remains to be measured and verified in 2013.
The liquid crystal layer (5) is typically laid down between glass substrates (1, 8) that have been coated with alignment (orientation) layers (4, 6). The amorphous Selenium (a-Se) layer (3) captures the x-Rays and coverts them into electron-hole pairs which are separated by a bias voltage applied between the transparent-conductive Indium-Tin-Oxide (ITO) electrodes (2, 7). The optical scanner reads the image through the substrate (8).
The preliminary evaluation of the XLV’s Modulation Transfer Function (MTF), shown below, which is a key parameter for assuring good resolution in clinical imaging, compares favorably with both direct and indirect, flat panel, x-ray, digital detectors available commercially today.