by John R. Fischer
, Senior Reporter | October 27, 2021
RaySearch Laboratories and Mevion Medical Systems are developing advanced treatment planning approaches to deliver FLASH therapy on Mevion’s S250i Proton Therapy System with HYPERSCAN.
FLASH therapy is an advanced form of radiotherapy currently under investigation. It is designed to deliver a noninvasive, ultra-high dose of radiation in less than one second to treat tumors effectively, while sparing healthy tissue. For their endeavor, RaySearch and Mevion are focused on FLASH intensity modulated proton therapy, an approach that alters proton beams to conform to the shape of tumors. It then applies multiple small proton beams to varying levels of intensity to precisely destroy the tumor.
FLASH therapies require sufficient dose coverage for large tumor volumes, which often are hundreds of cubic centimeters. Combined with the complexity of target shapes and constraints for surrounding organs at risk, this makes single-field FLASH treatments unlikely to provide acceptable dosimetric distribution relative to conventional treatment plans. To address this, Mevion and RaySearch have developed a "merged-field" technique that basically stitches together smaller fields to allow for FLASH doses to be delivered at a rate where the large volume is covered while surrounding organs are spared. Each of the smaller fields are a few cubic centimeters and can be modulated in size and weight with this approach and delivered over a non-FLASH timescale.
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"Our collaboration with RayStation will build upon this technique to develop the temporal and spatial modeling necessary to facilitate optimal target conformality and normal tissue sparing," Daniel Owen, R&D clinical engineer at Mevion, told HCB News.
The approach starts out by applying adjacent intensity-modulated small volumes at FLASH dose rates separately and then combining the individual small volumes to create a single large volume that can apply treatment effectively, while still sparing normal tissue. It is expected to combine both IMPT and FLASH into one delivery system, with each volume applied at FLASH dose rates that complement Mevion’s system.
The collaboration will focus on the calculation of FLASH weighted dose distributions including optimization and consideration of tissue type dependencies. For its part, RaySearch will utilize its Monte Carlo dose calculation system to come up with a final dose calculation and to determine optimal use of the technique with Mevion’s system. “We are now excited to explore how RayStation can create optimal FLASH plans for the HYPERSCAN system and to further deepen our partnership,” said Kjell Eriksson, chief science officer of RaySearch.