Fluid dynamic bowtie attenuators

Timothy P. Szczykutowicz; James Hermus

doi:10.1117/12.2077618

18 March 2015 Fluid dynamic bowtie attenuators

Timothy P. Szczykutowicz, James Hermus

Proceedings Volume 9412, Medical Imaging 2015: Physics of Medical Imaging; 94120X (2015) https://doi.org/10.1117/12.2077618
Event: SPIE Medical Imaging, 2015, Orlando, Florida, United States

Abstract

Fluence field modulated CT allows for improvements in image quality and dose reduction. To date, only 1-D modulators have been proposed, the extension to 2-D modulation is difficult with solid-metal attenuation-based modulators. This work proposes to use liquids and gas to attenuate the x-ray beam which can be arrayed allowing for 2-D fluence modulation. The thickness of liquid and the pressure for a given path length of gas were determined that provided the same attenuation as 30 cm of soft tissue at 80, 100, 120, and 140 kV. Gaseous Xenon and liquid Iodine, Zinc Chloride, and Cerium Chloride were studied. Additionally, we performed some proof-of-concept experiments in which (1) a single cell of liquid was connected to a reservoir which allowed the liquid thickness to be modulated and (2) a 96 cell array was constructed in which the liquid thickness in each cell was adjusted manually. Liquid thickness varied as a function of kV and chemical composition, with Zinc Chloride allowing for the smallest thickness; 1.8, 2.25, 3, and 3.6 cm compensated for 30 cm of soft tissue at 80, 100, 120, and 140 kV respectively. The 96 cell Iodine attenuator allowed for a reduction in both dynamic range to the detector and scatter to primary ratio. Successful modulation of a single cell was performed at 0, 90, and 130 degrees using a simple piston/actuator. The thickness of liquids and the Xenon gas pressure seem logistically implementable within the constraints of CBCT and diagnostic CT systems.

Citation Download Citation

Timothy P. Szczykutowicz and James Hermus "Fluid dynamic bowtie attenuators", Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94120X (18 March 2015); https://doi.org/10.1117/12.2077618

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