Ionization Chamber with Remote Preamplifier for Automatic Exposure Systems Used in X-Ray Diagnosis

摘要

Digital X-ray imaging systems provide high quantum efficiency and exposure dose decrease in the X-ray detector plane. The sensitivity of automatic exposure units of digital X-ray imaging systems should be substantially increased . The problem of sensitivity increase is made quite difficult by increased requirements for X-ray transparency of media located between patient and X-ray input detector plane. According to GOST R IEC 61223-3-1-200, the attenuation factor of automatic exposure dose control system detector is 1.11 . Distance between patient plane and input X-ray detector plane should be reduced to decrease X-ray image geometric unsharpness and radiation load on patient. This can be achieved by reducing the ionization chamber width. Within the last decade, the ionization chamber width in X-ray apparatuses was decreased from 12-10 to 6 mm against the background of virtually invariable sensitivity per area of measured (dominant) zone of the radiation detector. The sensitivity losses were 30-40% and were compensated by low-noise high-sensitivity electronics. The sensitivity of the electronics increased by an order of magnitude during recent time.