ESTRO 2023 - Abstract Book

S1746

Digital Posters

ESTRO 2023

Conclusion Our preliminary results seem to find a relationship between STN and tumor histology and the prescribed dose and fractionation schedule, for both PT and CIRT. Further analyses are mandatory to confirm our findings, including evaluation of potential clinical dose-modifying factors, histological subtype and individual patient radiosensitivity profiles, possibly in comparison with a control patient pool.

PO-1978 Develop the first optimization of LET integrated SPArc with voxel based FLASH dose rate (SPLASHLET)

G. Liu 1 , Q. Fan 2 , L. Zhao 3 , X. Li 3 , S. Dai 4 , S. Zhang 1 , X. Lu 2 , X. Ding 3

1 Wuhan Union Hospital, Cancer Center, Wuhan, China; 2 Wuhan University, School of Mathematics and Statistics, Wuhan, China; 3 Corewell Health William Beaumont University Hospital, Radiation Oncology, Royal Oak, USA; 4 Wuhan , School of Mathematics and Statistics, Wuhan, China Purpose or Objective to develop a novel treatment and planning technology enabling (1) Linear Energy Transfer(LET) painting (2) the voxel-wised FLASH dose rate; (3) high dose conformity and (4) simplied clinical workflow based on the Spot-scanning arc therapy (SPArc) platform through sequentially optimize the voxel-wised LET distribution and dose rate based on Spot-scanning arc therapy(SPArc). Materials and Methods this novel technique was implemented in an open-source proton planning platform(MatRad, Department of Medical Physics in Radiation Oncology, German Cancer Research Center-DKFZ). It optimizes with (1) the clinical dose-volume constraint based on dose distribution and (2) the clinical LET-volume constraint based on LET distribution and (3) the effective dose- average dose rate by minimizing the monitor unit(MU) constraint on spot weight and accelerator’s beam current sequentially, enabling the dynamic SPArc therapy realizes LET painting with voxel-based FLASH dose rate. This new optimization framework is able to minimize the overall cost function value combined with plan quality and voxel-based LET and dose rate constraints without introducing rigid filter, which will complicated the clinical treatment workflow and clinical implementation. A brain case was used for testing purposes. Dose-volume histogram(DVH), LET volume histogram(LVH) ， dose rate volume histogram(DRVH) and dose rate map were assessed. Results SPLASHLET plan could offer comparable dosimetric plan quality compared to the original SPArc plan (SPArcoriginal) through DVH comparison. The DRVH results indicated SPArcoriginal could not achieve FLASH using the clinic beam current configuration, but SPLASHLET could significantly not only improve V40Gy/s in target and region of interest(ROI) but also improve the mean LET in target and reduce the high LET in organ at risk (OAR) in comparison with SPArc. More specially, the mean LET in PTV was improve from 3.6(SPArcoriginal ) to 4.5(SPLASHLET ) keV/µm(fig1) the max LET was reduced from 5.0(SPArcoriginal ) to 4.5(SPLASHLET ) keV/µm(fig1), respectively. Meanwhile, compared to SPArc, SPLASHLET improved dose-averaged dose rate of V40Gy/s in PTV, optic chiasm from 0%, 0% to 100%, 81%,respectively(fig1).The optimal beam current per spot is simultaneously generated （ fig1 ） .