In recent years, new x-ray radiographic systems based on large area flat panel technology have revolutionized our
capability to produce digital x-ray radiographic images. However, these active matrix flat panel imagers (AMFPIs) are
extraordinarily expensive compared to the systems they are replacing. Thus there is a need for a low cost digital imaging
system for general applications in radiology. Different approaches have been considered to make lower cost, integrated
x-ray imaging devices for digital radiography, including: scanned projection x-ray, an integrated approach based on
computed radiography technology and optically demagnified x-ray screen/CCD systems. These approaches suffer from
either high cost or high mechanical complexity and do not have the image quality of AMFPIs. We have identified a new
approach - the X-ray Light Valve (XLV). The XLV has the potential to achieve the immediate readout in an integrated
system with image quality comparable to AMFPIs. The XLV concept combines three well-established and hence lowcost
technologies: an amorphous selenium (a-Se) layer to convert x-rays to image charge, a liquid crystal (LC) cell as an
analog display, and an optical scanner for image digitization. Here we investigate the spatial resolution possible with
XLV systems. Both a-Se and LC cells have both been shown separately to have inherently very high spatial resolution.
Due to the close electrostatic coupling in the XLV, it can be expected that the spatial resolution of this system will also
be very high. A prototype XLV was made and a typical office scanner was used for image digitization. The Modulation
Transfer Function was measured and the limiting factor was seen to be the optical scanner. However, even with this
limitation the XLV system is able to meet or exceed the resolution requirements for chest radiography.