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Proceedings Paper

Characterization of a novel photon counting detector for clinical CT: count rate, energy resolution, and noise performance
Author(s): William C. Barber; Einar Nygard; Jan S. Iwanczyk; Mengxi Zhang; Eric C. Frey; Benjamin M. W. Tsui; Jan C. Wessel; Nail Malakhov; Gregor Wawrzyniak; Neal E. Hartsough; Thulasi Gandhi; Katsuyuki Taguchi
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Paper Abstract

We report on a characterization study of a multi-row direct-conversion x-ray detector used to generate the first photon counting clinical x-ray computed tomography (CT) patent images. In order to provide the photon counting detector with adequate performance for low-dose CT applications, we have designed and fabricated a fast application specific integrated circuit (ASIC) for data readout from the pixellated CdTe detectors that comprise the photon counting detector. The cadmium telluride (CdTe) detector has 512 pixels with a 1 mm pitch and is vertically integrated with the ASIC readout so it can be tiled in two dimensions similar to those that are tiled in an arc found in 32-row multi-slice CT systems. We have measured several important detector parameters including the maximum output count rate, energy resolution, and noise performance. Additionally the relationship between the output and input rate has been found to fit a non-paralyzable detector model with a dead time of 160 nsec. A maximum output rate of 6 × 106 counts per second per pixel has been obtained with a low output x-ray tube for CT operated between 0.01 mA and 6 mA at 140 keV and different source-to-detector distances. All detector noise counts are less that 20 keV which is sufficiently low for clinical CT. The energy resolution measured with the 60 keV photons from a 241Am source is ~12%. In conclusion, our results demonstrate the potential for the application of the CdTe based photon counting detector to clinical CT systems. Our future plans include further performance improvement by incorporating drift structures to each detector pixel.

Paper Details

Date Published: 12 March 2009
PDF: 9 pages
Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 725824 (12 March 2009); doi: 10.1117/12.813915
Show Author Affiliations
William C. Barber, DxRay, Inc. (United States)
Einar Nygard, DxRay Inc. (United States)
Interon AS (Norway)
Jan S. Iwanczyk, DxRay, Inc. (United States)
Mengxi Zhang, The Johns Hopkins Univ. (United States)
Eric C. Frey, The Johns Hopkins Univ. (United States)
Benjamin M. W. Tsui, The Johns Hopkins Univ. (United States)
Jan C. Wessel, Interon AS (Norway)
Nail Malakhov, DxRay Inc. (United States)
Interon AS (Norway)
Gregor Wawrzyniak, Interon AS (Norway)
Neal E. Hartsough, DxRay, Inc. (United States)
Thulasi Gandhi, DxRay, Inc. (United States)
Katsuyuki Taguchi, The Johns Hopkins Univ. (United States)


Published in SPIE Proceedings Vol. 7258:
Medical Imaging 2009: Physics of Medical Imaging
Ehsan Samei; Jiang Hsieh, Editor(s)

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