Author: Amir Abdollahi, Celine Karle, Michele M. Kim, Constantinos Koumenis, Andrea Mairani, Erato Stylianou Markidou 👨🔬
Affiliation: Heidelberg Ion-Beam Therapy Center - Department of Radiation Oncology, German Cancer Research Centre(DKFZ), University of Pennsylvania, Physics Dep. University of Cyprus 🌍
Purpose: The aim is to compare FLASH dose-rate RT generated with protons and carbon (HIT) and compare to protons (UPenn) to provide evidence for equipotency of FLASH vs. standard RT to tumor growth control, while sparing normal tissues in preclinical models of thoracic and Head and neck irradiation.
Methods: RT studies were performed at UPenn and at HIT ensure physical dose between proton/carbon and FLASH/standard. Critically, it will also develop and implement approaches for harmonization of dosimetry between the two sites. We specifically perform a dose rate escalation study using 100 and 46 Gy/sec for protons and carbons respectively. A NIST-traceable Markus chamber delivered to HIT was used for cross calibration of their Pinpoint chamber in proton and carbon beams. These detectors were paired with electrometer Unidos PTW Webline from HIT. The delivery of multiple layers of Bragg peaks would be difficult for FLASH radiation delivery in short time scales, thus we have compared different ridge filters to provide dosimetry support and validation for these beam modifying devices. Measurements were performed using two different set ups using the 3 cm PMMA slab and the 3D printed mouse phantom (IΩΝ) that was designed with two inserts for a pint point chamber and for films.
Results: We are comparing dose at the Spread-Out-Bragg Peak with those at the entrance region. With ridge filters no proton beam energy adjusting is needed, while full coverage of the tumor is ensured. The study also explores carbon irradiation to optimize fractionation schemes and doses for improved tumor control and organ-at-risk sparing.
Conclusion: This study contributes to an improved understanding of interplay between parameters in FLASH radiotherapy, facilitating the optimization of clinical applications and development of suitable modalities. The intercomparison of these parameters between the two institutions can unravel their importance for the FLASH effect.