L7452:In ordinar y X-ra y detectors, deter ioration in performance such as a drop in sensitivity and an increase in dark video output occurs due to X-ray irradiation. Likewise, flat panel sensor characteristics deteriorate due to X-ray irradiation. For example, an FSP type flat panel sensor with an aluminum top cover intended for non-destructive inspection is designed for use at a tube voltage from 20 kV to 100 kV, and can be used up to an accumulated dose of 8.7 kGy (one million roentgens) if used under tube voltage 100 kV.
When the photosensitive area is uniformly irradiated with X-rays, the dark current also increases almost uniformly over the photosensitive area. The dark current might partially increase in the photosensitive area, but this can be eliminated by dark image correction. When the partial increase in dark video output caused by increased dark current has exceeded the dark image correction limit, the flat panel sensor should be replaced as a consumable part. The life of flat panel sensors can be extended by setting the X-ray dose to a lower level within the detectable range and by preventing X-rays from irradiating the flat panel sensor except during imaging. Another effective way to extend the detector life is to use pulsed X-rays.
