Design of a digital, motion-free mechanism for fluence field modulation

Scott S. Hsieh; Shuai Leng; Lifeng Yu; Cynthia H. McCollough; Adam S. Wang

doi:10.1117/12.2611559

4 April 2022 Design of a digital, motion-free mechanism for fluence field modulation

Scott S. Hsieh, Shuai Leng, Lifeng Yu, Cynthia H. McCollough, Adam S. Wang

Proceedings Volume 12031, Medical Imaging 2022: Physics of Medical Imaging; 120310O (2022) https://doi.org/10.1117/12.2611559
Event: SPIE Medical Imaging, 2022, San Diego, California, United States

Abstract

Fluence field modulation (FFM) using dynamic pre-patient attenuators could reduce radiation dose while preserving image quality by optimizing the distribution of x-ray photons incident on the patient. However, past dynamic attenuators require mechanical action that is challenging to implement in diagnostic CT scanners and generate a large variety of system states that makes calibration complex. To circumvent these difficulties, we propose a motion-free mechanism for FFM that uses electromagnetic deflection of the focal spot, also called flying focal spot (FFS), together with interference patterns generated from fixed metal gratings. Our proposed design is digital in that only a limited number of fluence fields is possible, but the fluence field from each focal spot position is stable with respect to source perturbation, simplifying calibration. Intermediate fluence fields can be virtually achieved during reconstruction by using either statistical reconstruction or rebinning. We describe the geometric constraints for our FFM mechanism and illustrate some of the possible fluence fields that can be achieved.

Citation Download Citation

Scott S. Hsieh, Shuai Leng, Lifeng Yu, Cynthia H. McCollough, and Adam S. Wang "Design of a digital, motion-free mechanism for fluence field modulation", Proc. SPIE 12031, Medical Imaging 2022: Physics of Medical Imaging, 120310O (4 April 2022); https://doi.org/10.1117/12.2611559

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KEYWORDS

Attenuators

Metals

Modulation

Calibration

X-rays

Fluctuations and noise

Photons

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