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한종철,윤성만,윤한빈,감수화,조승룡,Thorsten G. Achterkirchen,김호경 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.5
Active pixel design using the complementary metal-oxide-semiconductor (CMOS) process is acompelling solution for use in X-ray imaging detectors because of its excellent electronic noisecharacteristics. We have investigated the imaging performance of a CMOS active pixel photodiodearray coupled to a granular phosphor through a fiber-optic faceplate for mammographic applications. The imaging performance included the modulation-transfer function (MTF), noise-power spectrum(NPS), and detective quantum efficiency (DQE). Because we observed a nonlinear detector responseat low exposures, we used the linearization method for the analysis of the DQE. The linearizationmethod uses the images obtained at detector input, which are converted from those obtained atdetector output by using the inverse of the detector response. Compared to the conventionalmethod, the linearization method provided almost the same MTF and a slightly lower normalizedNPS. However, the difference between the DQE results obtained by using the two methods wassignificant. We claim that the conventional DQE analysis of a detector having a nonlinear responsecharacteristic can yield wrong results. Under the standard mammographic imaging condition, weobtained a DQE performance that was competitive with the performances of conventional flat-panelmammography detectors. We believe that the CMOS detector investigated in this study can besuccessfully used for mammography.