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Proceedings Paper

Optimized intensity modulation for a dynamic beam attenuator in x-ray computed tomography
Author(s): Sascha Manuel Huck; George S. K. Fung; Katia Parodi; Karl Stierstorfer
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Paper Abstract

In our previous study we successfully built a novel sheet-based dynamic beam attenuator (sbDBA) for fluence field modulation in X-ray computed tomography (CT) and performed a first-time experimental validation. In this work, we focus on the optimization of the DBA transmission properties for a given object. In clinical routine, CT scanners must cope with various attenuation properties differing from patient to patient. Typically, the attenuation of patients is high in the center of the fan beam, decreasing towards the periphery. The attenuation profiles of an object can also change for different X-ray tube positions. These variations cause unfavorable imbalances of image quality in the reconstructed object. Typically, the peripheral region, which is generally of minor diagnostically relevance, has relatively lower noise than the central region because the rays contributing to the peripheral region are less attenuated. This imbalance can be reduced by using beam-shaping prefilters, e.g. bowtie filters, attenuating the propagated intensity towards the periphery in a predefined, static profile. Bowtie filters, however, are not capable of dynamically adapting their attenuation to the attenuation profile of the patient. This can be accomplished by using dynamic beam attenuators (DBA) where the fan beam intensity can dynamically be modulated on a view-by-view basis, reducing noise inhomogeneities and enabling region-of-interest (ROI) imaging. Different scenarios (no attenuator, tube current modulation, conventional bowtie filter, the sbDBA and an ideal DBA) are compared in terms of image quality. The optimized sbDBA with tube current modulation (TCM) not only reduces the total radiation dose but also allows for spatial selection of intensity as required for ROI imaging.

Paper Details

Date Published: 1 March 2019
PDF: 7 pages
Proc. SPIE 10948, Medical Imaging 2019: Physics of Medical Imaging, 1094824 (1 March 2019); doi: 10.1117/12.2511704
Show Author Affiliations
Sascha Manuel Huck, Siemens Healthcare GmbH (Germany)
Ludwig-Maximilians-Univ. München (Germany)
George S. K. Fung, Siemens Medical Solutions USA, Inc. (United States)
Johns Hopkins Univ. School of Medicine (United States)
Katia Parodi, Ludwig-Maximilians-Univ. München (Germany)
Karl Stierstorfer, Siemens Healthcare GmbH (Germany)

Published in SPIE Proceedings Vol. 10948:
Medical Imaging 2019: Physics of Medical Imaging
Taly Gilat Schmidt; Guang-Hong Chen; Hilde Bosmans, Editor(s)

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