Ponente
Descripción
Background & Aims: In this study, we propose a strategy for multi-beam FLASH-PT combined with IMPT, applied to a meningioma case. The objective is to leverage the benefits of FLASH Bragg Peak-in-target beams in conjunction with IMPT. For this work, we defined “the FLASH effect” to occur in healthy tissue if irradiated with a minimum dose of 5 Gy, with a dose modifying factor (DMF) of 1.25.
Material and Methods: Using Raystation (Version 11B) we created a two-fraction FLASH plan (9 Gy per fraction, 18 Gy in total, keeping the clinical BED) with the same 4-beam arrangement as the clinical plan. We chose a different beam direction as the FLASH beam for each fraction. The remaining CTV was irradiated with three IMPT beams. We applied the DMF to the brainstem and an area of the brainstem unavoidable in the clinical treatment, the irradiated brainstem (IB), in the FLASH-DMF plan. We adjusted the clinical plan to match the same fractionation scheme as the FLASH plan ("CONV") and compared it to the FLASH-DMF plan.
Results: Figure 1 illustrates the dose distribution for CONV (a) and FLASH-DMF (b), and the dose-volume histogram comparing both plans (c). 1c Both plans had a V_95%of9Gy above 99 %, a comparable conformity index (0.54 and 0.60 for CONV and FLASH_DMF) and a homogeneity index (both 0.06). After applying the DMF, the near maximum dose in the brainstem (D_2%) was reduced by 3 Gy.
Conclusions: We have shown that multi-beam FLASH-PT is possible for the current meningioma case, where toxicity in the brainstem was reduced because of the FLASH effect. Future work will include the dose rate analysis.
Figure 1:
[1]: http://jleitao153915012024.imgur.com/all/?third_party=1
[2]: https://imgur.com/rtrl6sA
