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Is Spot-Scanning Proton Beam Therapy Ready for the Single Target Brain Stereotactic Radiosurgery? A Dosimetric Comparison Study Among VMAT, SPArc and IMPT

S Chang*, G Liu, P Chinnaiyan, L Zhao, W Zheng, D Yan, I Grills, C Stevens, P Kabolizadeh, X Li, X Ding, William Beaumont Hospital, Royal Oak, MI


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Spot-scanning Proton Arc(SPArc) therapy has been merging as a new treatment technique because of its superior dosimetric quality and robustness compared to the conventional Intensity Modulated Proton Therapy (IMPT). The study explored the feasibility of utilizing SPArc in comparison with the conventional IMPT and VMAT in the brain SRS.

A brain SRS model is established to set as a clinical decision tool among different treatment modalities. The model simulates different target locations and different sizes such as deep central and peripheral regions. The different target volume was created from 0.3cc; to 24.42cc (Fig. 1). Three planning groups: IMPT, SPArc and VMAT were generated using the same robust optimization parameters (2mm setup and 3.5% range uncertainty for proton planning and 2mm setup uncertainty for VMAT planning). Seven brain metastases patient previous treated with Gamma Knife were retrospectively selected to validate the brain SRS model.

In comparison with IMPT, VMAT clearly showed its advantage in the CI and R50 in any target size (<24.42cc) or locations where a sharp dose fall-off is clinically desired. In comparison with VMAT, SPArc has an equivalent or better CI in any size of peripheral targets and deep centrally located targets which were bigger than 7.32cc. At meanwhile, SPArc significantly reduced the normal brain tissue dose. For the deep centrally located tumor smaller than 7.32cc, VMAT plan still offered better dose CI. Seven clinical cases shows a similar trend and dosimetric results compared to the brain SRS model. A clinical decision of an optimal treatment could be made according to the size and location of the brain metastases(Table 1).

SPArc showed its potential advantage to offer lower dose to the brain tissue over VMAT with an equivalent or higher CI in the peripheral brain lesion and deep centrally located lesion bigger than 7.32cc.

Funding Support, Disclosures, and Conflict of Interest: Research fund from Ion Beam Application. Xuanfeng Ding, Xiaoqiang and Di Yan has a patent related to particle arc therapy


Not Applicable / None Entered.


TH- External Beam- Particle/high LET therapy: Carbon ion therapy - treatment planning/virtual clinical studies/adaptive therapy

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