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Proceedings Paper

Microcomputed tomography with a photon-counting x-ray detector
Author(s): E. C. Frey; K. Taguchi; M. Kapusta; J. Xu; T. Orskaug; I. Ninive; D. Wagenaar; B. Patt; B. M. W. Tsui
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Paper Abstract

In this work we used a novel CdTe photon counting x-ray detector capable of very high count rates to perform x-ray micro-computed tomography (microCT). The detector had 2 rows of 384 square pixels each 1 mm in size. Charge signals from individual photons were integrated with a shaping time of ~60 ns and processed by an ASIC located in close proximity to the pixels. The ASIC had 5 energy thresholds with associated independent counters for each pixel. Due to the thresholding, it is possible to eliminate dark-current contributions to image noise. By subtracting counter outputs from adjacent thresholds, it is possible to obtain the number of x-ray photon counts in 5 adjacent energy windows. The detector is capable of readout times faster than 5 ms. A prototype bench-top specimen μCT scanner was assembled having distances from the tube to the object and detector of 11 cm and 82 cm, respectively. We used a conventional x-ray source to produce 80 kVp x-ray beams with tube currents up to 400 μA resulting in count rates on the order of 600 kcps per pixel at the detector. Both phantoms and a dead mouse were imaged using acquisition times of 1.8 s per view at 1° steps around the object. The count rate loss (CRL) characteristics of the detector were measured by varying the tube current and corrected for using a paralyzable model. Images were reconstructed using analytical fan-beam reconstruction. The reconstructed images showed good contrast and noise characteristics and those obtained from different energy windows demonstrated energy-dependent contrast, thus potentially allowing for material decomposition.

Paper Details

Date Published: 15 March 2007
PDF: 6 pages
Proc. SPIE 6510, Medical Imaging 2007: Physics of Medical Imaging, 65101R (15 March 2007); doi: 10.1117/12.711647
Show Author Affiliations
E. C. Frey, Johns Hopkins Univ. (United States)
K. Taguchi, Johns Hopkins Univ. (United States)
M. Kapusta, Gamma Medica-Ideas (United States)
J. Xu, Johns Hopkins Univ. (United States)
T. Orskaug, Gamma Medica-Ideas (United States)
I. Ninive, Gamma Medica-Ideas (United States)
D. Wagenaar, Gamma Medica-Ideas (United States)
B. Patt, Gamma Medica-Ideas (United States)
B. M. W. Tsui, Johns Hopkins Univ. (United States)

Published in SPIE Proceedings Vol. 6510:
Medical Imaging 2007: Physics of Medical Imaging
Jiang Hsieh; Michael J. Flynn, Editor(s)

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