Radiochromic Film Dosimetry for VHEE and UHDR: Considerations for the CLEAR Facility and Comparisons with Alanine, RPL and Dosimetry Phantoms

TL;DR

This paper evaluates the use of radiochromic films for dosimetry in very high energy electron radiotherapy, addressing practical challenges and proposing protocols to improve measurement accuracy, with comparisons to other dosimetry methods.

Contribution

It provides a standardized protocol for RCF dosimetry in VHEE and FLASH, demonstrating reliable measurements and addressing common sources of error in the process.

Findings

RCF measurements agree within 5% of alanine dosimeters for VHEE beams

Identified key error sources in RCF preparation and scanning

Proposed mitigation strategies improve dosimetry accuracy

Abstract

Radiochromic films (RCFs) offer valuable two-dimensional dosimetry capabilities with a conceptually simple operating principle that requires minimal investment, making them particularly suitable for very high energy electron (VHEE) FLASH dosimetry where dosimetry standards are currently lacking. However, achieving high-accuracy measurements with RCFs presents significant practical challenges. Without the standardised protocols that ensure reliable outcomes across applications and facilities, knowledge of RCF behaviour becomes essential. This paper identifies common sources of error in RCF preparation, scanning, and processing while proposing specific mitigation strategies to improve accuracy and efficiency. Using our optimised RCF protocol at the CLEAR facility, we demonstrate relative agreement within 5% compared to alanine dosimeters when measuring Gaussian VHEE beams, establishing a foundation for reliable dosimetry in these advanced radiotherapy applications.