Development of a portable digital radiographic system based on FOP-coupled CMOS image sensor and its performance evaluation
As a continuation of our digital X-ray imaging sensor R&D, we have developed a cost-effective, portable, digital radiographic system based on the CMOS image sensor coupled with a fiber optic plate (FOP) and a conventional scintillator. The imaging system mainly consists of a commercially available CMOS image sensor of 48times48 mum2 pixel size and 49.2times49.3 mm2 active area (RadEyetrade2 from Rad-icon Imaging Corp.), a FOP bundled with several millions of glass fibers of about 6 mum in diameter, a phosphor screen such as Min-R or Lanex series, a readout IC board and a GUI software we developed, and a battery-operated X-ray generator (20-60 kVp; up to 1 mA). Here the FOP was incorporated into the imaging system to reduce the performance degradation of the CMOS sensor and the readout IC board caused by irradiation, and also to improve image qualities. In this paper, we describe each imaging component of the fully-integrated portable digital radiographic system in detail, and also present its performance analysis with experimental measurements and acquired X-ray images in terms of system response with exposure, contrast-to-noise ratio (CNR), modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE).