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Proceedings Paper

Dual-energy x-ray absorptiometry using a multielement high-purity germanium detector array: technical considerations
Author(s): Eric L. Gingold; Bruce H. Hasegawa; Christopher E. Cann; Andrew D. Jeffries
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Paper Abstract

We have designed and built a dual-energy x-ray absorptiometry (DXA) instrument for the measurement of bone density in-vivo using a high-purity germanium detector array. This system uses a fan beam geometry and a strip of 24 2 mm wide detectors to function as a scanned projection quantitative imaging system. The use of photon-counting detectors with a k-edge filtered x-ray spectrum avoids spectral overlap in the dual-energy data, and optimizes dose efficiency. The multielement detector is energy-sensitive and capable of high counting rates (106 counts per second per element). Dual-energy data is acquired in a single short exposure, enabling high-speed scanning. We have examined the temporal stability of the system, and developed strategies for controlling against thermally induced drift. Counting rate nonlinearity due to dead-time losses was modelled, and a correction for this phenomenon was implemented. We measured scattered radiation and investigated scatter removal schemes. The spatial resolution of the system was evaluated, and the entrance skin exposure to the patient was measured using thermoluminescent dosimeters (TLDs). A noise reduction algorithm was incorporated into the scanner which exploits the correlation of the pixel noise in the basis material images, derived from dual-energy data, to improve signal-to-noise without compromising edge sharpness or quantitative accuracy. This instrument shows promise as a research tool for the investigation on new scanning methodologies in bone-mineral densitometry.

Paper Details

Date Published: 1 June 1992
PDF: 10 pages
Proc. SPIE 1651, Medical Imaging VI: Instrumentation, (1 June 1992);
Show Author Affiliations
Eric L. Gingold, Univ. of California/San Francisco (United States)
Bruce H. Hasegawa, Univ. of California/San Francisco (United States)
Christopher E. Cann, Univ. of California/San Francisco (United States)
Andrew D. Jeffries, Imatron, Inc. (United States)

Published in SPIE Proceedings Vol. 1651:
Medical Imaging VI: Instrumentation
Rodney Shaw, Editor(s)

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