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Proceedings Paper

An aging study of the signal and noise characteristics in large-area CMOS detectors
Author(s): Jong Chul Han; Seungman Yun; Chang Hwy Lim; Tae Gyun Youm; Sung Kyn Heo; Tae Woo Kim; Ian Cunningham; Ho Kyung Kim
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Paper Abstract

For a detector consisting of a phosphor screen and a photodiode array made by complementary metal-oxidesemiconductor (CMOS) process, we have experimentally re-investigated the long-term stability of the signal and noise characteristics as a function of the accumulated dose at the entrance surface of the detector in addition to the previous study [IEEE Trans. Nucl. Sci. 56(3) 1121 (2009)]. The irradiation and analysis were more systematically performed. We report the aging effect in image quality in terms of dark pixel signal, dynamic range, modulation-transfer function (MTF), and noise-power spectrum (NPS). Unlike the previous study, the electronic noise was dominantly increased with the total dose and the other statistical and structural noise sources were nearly independent on the cumulative dose. Similarly, the increase of dark pixel signal and the related noise gradually reduces the dynamic range as the total dose increases. While MTF was almost insensitive to the total dose, degradation in NPS was observed. Therefore, preprocessing without properly updated offset and gain images would underestimate the detective quantum efficiency when performing quality control of a detector in the field. Restoration of degraded dark signals due to aging is demonstrated by annealing the aged detector with thermal activation energy. This study provides a motivation that the periodic monitoring of the imagequality degradation is of great importance for the long-term and healthy use of digital x-ray imaging detectors.

Paper Details

Date Published: 22 March 2010
PDF: 8 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76223Y (22 March 2010); doi: 10.1117/12.844159
Show Author Affiliations
Jong Chul Han, Pusan National Univ. (Korea, Republic of)
Seungman Yun, Pusan National Univ. (Korea, Republic of)
Chang Hwy Lim, Pusan National Univ. (Korea, Republic of)
Tae Gyun Youm, Pusan National Univ. (Korea, Republic of)
Sung Kyn Heo, E-WOO Technology Co., Ltd. (Korea, Republic of)
Tae Woo Kim, E-WOO Technology Co., Ltd. (Korea, Republic of)
Ian Cunningham, Robarts Research Institute (Canada)
Ho Kyung Kim, Pusan National Univ. (Korea, Republic of)


Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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