Fluid-filled dynamic bowtie filter: a feasibility study

Picha Shunhavanich; Scott S. Hsieh; Norbert J. Pelc

doi:10.1117/12.2081673

18 March 2015 Fluid-filled dynamic bowtie filter: a feasibility study

Picha Shunhavanich, Scott S. Hsieh, Norbert J. Pelc

Proceedings Volume 9412, Medical Imaging 2015: Physics of Medical Imaging; 94121L (2015) https://doi.org/10.1117/12.2081673
Event: SPIE Medical Imaging, 2015, Orlando, Florida, United States

Abstract

By varying its thickness to compensate for the different path length through the patient as a function of fan angle, a pre-patient bowtie filter modulates flux distribution to reduce patient dose, scatter, and detector dynamic range, and to improve image quality. A dynamic bowtie filter is superior to its traditional, static counterpart in its ability to adjust its thickness along different fan and view angles to suit a specific patient and task. Among the proposed dynamic bowtie designs, the piecewise-linear and the digital beam attenuators offer more flexibility than conventional filters, but rely on analog positioning of a limited number of wedges. In this work, we introduce a new approach with digital control, called the fluid-filled dynamic bowtie filter. It is a two-dimensional array of small binary elements (channels filled or unfilled with attenuating liquid) in which the cumulative thickness along the x-ray path contributes to the bowtie’s total attenuation. Using simulated data from a pelvic scan, the performance is compared with the piecewise-linear attenuator. The fluid-filled design better matches the desired target attenuation profile and delivers a 4.2x reduction in dynamic range. The variance of the reconstruction (or noise map) can also be more homogeneous. In minimizing peak variance, the fluid-filled attenuator shows a 3% improvement. From the initial simulation results, the proposed design has more control over the flux distribution as a function of both fan and view angles.

Citation Download Citation

Picha Shunhavanich, Scott S. Hsieh, and Norbert J. Pelc "Fluid-filled dynamic bowtie filter: a feasibility study", Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94121L (18 March 2015); https://doi.org/10.1117/12.2081673

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