Traditional CT image acquisitions use bowtie filters to enable dose reduction. However, accurate patient centering within the bore of the CT scanner takes time and is often difficult to achieve precisely. Patient miscentering can result in significant dose, reconstruction noise, and CT number variations–raising overall exposure requirements. Approaches to estimate patient position from scout scans and perform dynamic spatial beam filtration during acquisition are developed and applied in physical experiments on a CT test bench using different beam filtration strategies. While various dynamic beam modulation strategies have been proposed, we focus on two different approaches: 1) simple attenuation-based beam modulation using a translating bowtie filter, and 2) dynamic beam modulation using multiple aperture devices, an emerging beam filtration strategy base on binary filtration of the x-ray beam using variable width slits in a high-density beam blocker. Improved dose utilization and more consistent image performance is demonstrated for miscentered objects and dynamic beam filtration as compared to static filtration. The new methodology has the potential to relax patient centering requirements within the scanner, reduce set-up time, and facilitate additional CT dose reductions.
Andrew Mao, William Shyr, Grace J. Gang, and J. Webster Stayman, "Dynamic beam filtering for miscentered patients," Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 105730U (Presented at SPIE Medical Imaging: February 13, 2018; Published: 9 March 2018); https://doi.org/10.1117/12.2293696.
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