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Proceedings Paper

The CNR method in scan angle optimization of tomosynthesis and its limitations
Author(s): Baorui Ren; Chris Ruth; Yiheng Zhang; Andrew Smith; Cornell Williams; Brad Polischuk; Zhenxue Jing
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Paper Abstract

The performance optimization of tomosynthesis is very challenging as it involves multiple system parameters to be optimized towards multiple figures of merit (FOM). Common approach is to take a selected few FOMs and optimize them under more confined conditions. While this kind of study helps us to gain more insights, extra precautions are needed when one tries to generalize the conclusions. Several reported works have shown that increasing the scan angle improves the contrast to noise ratio (CNR), which made the authors conclude that from the CNR perspective, large scan angle has advantages over small angle in tomosynthesis. In this study, we investigated the dependence of CNR on the scan angle while other system parameters were fixed. We found that improvement of CNR with large scan angle in those published studies was actually due to reconstruction algorithm and associated filtering effect but not due to the scan angle itself. To reveal this property, we selected six filters to cover a board range of possible shapes, and showed CNR variations with different filters. Besides, we also studied the ML-EM and SART iterative reconstruction algorithms, and obtained their equivalent Fourier filters numerically. The change of the equivalent filter shapes of iterative methods at different scan angle explained the observed CNR dependence on the scan angles. We conclude that larger scan angle does not have any intrinsic CNR advantage over small one in tomosynthesis. The observed CNR gain at large angle is an effect from the reconstruction filters. Therefore CNR based optimization study need to be carried out without the potential bias from filters.

Paper Details

Date Published: 29 April 2009
PDF: 10 pages
Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 72585W (29 April 2009); doi: 10.1117/12.813918
Show Author Affiliations
Baorui Ren, Hologic, Inc. (United States)
Chris Ruth, Hologic, Inc. (United States)
Yiheng Zhang, Hologic, Inc. (United States)
Andrew Smith, Hologic, Inc. (United States)
Cornell Williams, Hologic, Inc. (United States)
Brad Polischuk, Hologic, Inc. (United States)
Zhenxue Jing, Hologic, Inc. (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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