Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

TL;DR

This review discusses dosimetric tools suitable for FLASH radiotherapy, emphasizing the potential of radioluminescence and Cherenkov emission detectors to address high dose rate challenges and elucidate radiobiological mechanisms.

Contribution

It highlights the advantages of luminescent detectors in high dose rate environments and their role in understanding the FLASH effect through real-time oxygenation mapping.

Findings

Cherenkov and scintillation detectors offer high spatial and temporal resolution.

Luminescent detectors are dose-rate independent, suitable for FLASH dosimetry.

Real-time oxygenation mapping can elucidate FLASH radiobiological mechanisms.

Abstract

While spatial dose conformity delivered to a target volume has been pushed to its practical limits with advanced treatment planning and delivery, investigations in novel temporal dose delivery are unfolding new mechanisms. Recent advances in ultra-high dose radiotherapy, abbreviated as FLASH, indicate the potential for reduction in healthy tissue damage while preserving tumor control. FLASH therapy relies on very high dose rate of > 40Gy/sec with sub-second temporal beam modulation, taking a seemingly opposite direction from the conventional paradigm of fractionated therapy. FLASH brings unique challenges to dosimetry, beam control, and verification, as well as complexity of radiobiological effective dose through altered tissue response. In this review, we compare the dosimetric methods capable of operating under high dose rate environments. Due to excellent dose-rate independence, superior spatial (~<1 mm) and temporal (~ns) resolution achievable with Cherenkov and scintillation-based detectors, we show that luminescent detectors have a key role to play in the development of FLASH-RT, as the field rapidly progresses towards clinical adaptation. Additionally, we show that the unique ability of certain luminescence-based methods to provide tumor oxygenation maps in real-time with submillimeter resolution can elucidate the radiobiological mechanisms behind the FLASH effect. In particular, such techniques will be crucial for understanding the role of oxygen in mediating the FLASH effect.