Performance Characteristics of a CdTe-Based Digital Gamma Imaging System with a 75Se Radioisotope

Abstract

As a continuation of our digital radiographic sensor R&D, we have developed a digital gamma imaging system based upon the cadmium-telluride (CdTe) photoconductor for the applications of industrial gamma-imaging. The imaging system consists of a commercially-available CMOS pixel array of a 100 × 100 μm2 pixel size and a 5.4 × 151.0 mm2 active area, coupled with a 750-μm-thick CdTe photoconductor, and a collimated selenium (75Se) radioisotope of an about 2.3 × 1012 Bq activity and a physical size of 3.0 mm in diameter. In this study, we, for the first time, succeeded in obtaining useful gamma images of several test phantoms with the 75Se radioisotope from the imaging system and evaluated its imaging performance in terms of the line spread function (LSF), the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE). For comparison, we also tested its X-ray imaging performance with a microfocus X-ray tube of an about 5 μm focal spot size at an operation condition of 90 kVp and 100 μA. According to our test results, the designed imaging system seems to be promising for our ongoing application of nondestructive testings, provided that the effective source size of the 75Se radioisotope can be further limited.