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Cancers 2017, 9(12), 170; https://doi.org/10.3390/cancers9120170

Synchrotron-Based Pencil Beam Scanning Nozzle with an Integrated Mini-Ridge Filter: A Dosimetric Study to Optimize Treatment Delivery

1
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
2
Department of Radiation Oncology, Sichuan Cancer Hospital & Institute, Chengdu 610041, China
3
Key Laboratory of Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China
4
Research & Development Group, Hitachi, Ltd., Hitachi-shi, Ibaraki-ken 3178511, Japan
5
Healthcare Business Unit, Particle Therapy Division, Hitachi, Ltd., Hitachi-shi, Ibaraki-ken 3178511, Japan
6
Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
*
Author to whom correspondence should be addressed.
Received: 10 October 2017 / Revised: 5 December 2017 / Accepted: 11 December 2017 / Published: 13 December 2017
(This article belongs to the Special Issue Proton and Carbon Ion Therapy)
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Abstract

A mini-ridge filter is often used to widen the Bragg peak in the longitudinal direction at low energies but not high energies. To facilitate the clinical use of a mini-ridge filter, we performed a planning study for the feasibility of a mini-ridge filter as an integral part of the synchrotron nozzle (IMRF). Dose models with and without IMRF were commissioned in a commercial Treatment planning system (TPS). Dosimetric characteristics in a homogenous water phantom were compared between plans with and without IMRF for a fixed spread-out Bragg peak width of 4 cm with distal ranges varying from 8 to 30 g/cm2. Six clinical cases were then used to compare the plan quality between plans. The delivery efficiency was also compared between plans in both the phantom and the clinical cases. The Bragg peak width was increased by 0.18 cm at the lowest energy and by only about 0.04 cm at the highest energy. The IMRF increased the spot size (σ) by up to 0.1 cm at the lowest energy and by only 0.02 cm at the highest energy. For the phantom, the IMRF negligibly affected dose at high energies but increased the lateral penumbra by up to 0.12 cm and the distal penumbra by up to 0.06 cm at low energies. For the clinical cases, the IMRF slightly increased dose to the organs at risk. However, the beam delivery time was reduced from 18.5% to 47.1% for the lung, brain, scalp, and head and neck cases, and dose uniformities of target were improved up to 2.9% for these cases owing to the reduced minimum monitor unit effect. In conclusion, integrating a mini-ridge filter into a synchrotron nozzle is feasible for improving treatment efficiency without significantly sacrificing the plan quality. View Full-Text
Keywords: proton therapy; ridge filter; pencil beam scanning proton therapy; ridge filter; pencil beam scanning
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Wang, X.; Li, Y.; Zhang, X.; Li, H.; Miyazaki, K.; Fujimoto, R.; Akiyama, H.; Gillin, M.T.; Poenisch, F.; Sahoo, N.; Grosshans, D.; Gunn, B.; Frank, S.J.; Wang, P.; Lang, J.; Hou, Q.; Zhu, X.R. Synchrotron-Based Pencil Beam Scanning Nozzle with an Integrated Mini-Ridge Filter: A Dosimetric Study to Optimize Treatment Delivery. Cancers 2017, 9, 170.

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