FLASH Radiotherapy and the Use of Radiation Dosimeters

Sarkar Siddique; Harry E Ruda; James C L Chow

doi:10.3390/cancers15153883

FLASH Radiotherapy and the Use of Radiation Dosimeters

Cancers (Basel). 2023 Jul 30;15(15):3883. doi: 10.3390/cancers15153883.

Authors

Sarkar Siddique¹, Harry E Ruda^{2

3}, James C L Chow^{4

5}

Affiliations

¹ Department of Physics, Toronto Metropolitan University, Toronto, ON M5B 2K3, Canada.
² Centre of Advance Nanotechnology, Faculty of Applied Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada.
³ Department of Materials Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada.
⁴ Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 1X6, Canada.
⁵ Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada.

Abstract

Radiotherapy (RT) using ultra-high dose rate (UHDR) radiation, known as FLASH RT, has shown promising results in reducing normal tissue toxicity while maintaining tumor control. However, implementing FLASH RT in clinical settings presents technical challenges, including limited depth penetration and complex treatment planning. Monte Carlo (MC) simulation is a valuable tool for dose calculation in RT and has been investigated for optimizing FLASH RT. Various MC codes, such as EGSnrc, DOSXYZnrc, and Geant4, have been used to simulate dose distributions and optimize treatment plans. Accurate dosimetry is essential for FLASH RT, and radiation detectors play a crucial role in measuring dose delivery. Solid-state detectors, including diamond detectors such as microDiamond, have demonstrated linear responses and good agreement with reference detectors in UHDR and ultra-high dose per pulse (UHDPP) ranges. Ionization chambers are commonly used for dose measurement, and advancements have been made to address their response nonlinearities at UHDPP. Studies have proposed new calculation methods and empirical models for ion recombination in ionization chambers to improve their accuracy in FLASH RT. Additionally, strip-segmented ionization chamber arrays have shown potential for the experimental measurement of dose rate distribution in proton pencil beam scanning. Radiochromic films, such as Gafchromic^TM EBT3, have been used for absolute dose measurement and to validate MC simulation results in high-energy X-rays, triggering the FLASH effect. These films have been utilized to characterize ionization chambers and measure off-axis and depth dose distributions in FLASH RT. In conclusion, MC simulation provides accurate dose calculation and optimization for FLASH RT, while radiation detectors, including diamond detectors, ionization chambers, and radiochromic films, offer valuable tools for dosimetry in UHDR environments. Further research is needed to refine treatment planning techniques and improve detector performance to facilitate the widespread implementation of FLASH RT, potentially revolutionizing cancer treatment.

Keywords: FLASH radiotherapy; detectors; dosimetry; ultra-high dose rate radiotherapy.

Publication types

Review

Grants and funding

NFRFE-2022-00707/New Frontiers in Research Fund - Exploration