4D in vivo dosimetry for a FLASH electron beam using radiation-induced acoustic imaging

Kristina Bjegovic; Leshan Sun; Prabodh Pandey; Veljko Grilj; Paola Ballesteros-Zebadua; Ryan Paisley; Gilberto Gonzalez; Siqi Wang; Marie Catherine Vozenin; Charles L Limoli; Shawn Liangzhong Xiang

doi:10.1088/1361-6560/ad4950

4D in vivo dosimetry for a FLASH electron beam using radiation-induced acoustic imaging

Phys Med Biol. 2024 May 31;69(11). doi: 10.1088/1361-6560/ad4950.

Authors

Affiliations

¹ The Department of Biomedical Engineering, University of California, Irvine, CA 92617, United States of America.
² Department of Radiological Sciences, University of California, Irvine, Irvine, CA 92697, United States of Americaica.
³ Laboratory of Radiation Oncology, Radiation Oncology Service and Oncology Department, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
⁴ Laboratory of Medical Physics, National Institute of Neurology and Neurosurgery, Mexico City, Mexico.
⁵ Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States of America.
⁶ Sector of Radiobiology applied to Radiation Oncology, Radiation Oncology Service, Geneva University Hospital and University of Geneva, Geneva, Switzerland.
⁷ Department of Radiation Oncology, University of California, Irvine, Irvine, CA 92697-2695, United States of America.
⁸ Beckman Laser Institute & Medical Clinic, University of California, Irvine, Irvine, CA 92612, United States of America.

PMID: 38722574
DOI: 10.1088/1361-6560/ad4950

Abstract

Objective. The primary goal of this research is to demonstrate the feasibility of radiation-induced acoustic imaging (RAI) as a volumetric dosimetry tool for ultra-high dose rate FLASH electron radiotherapy (FLASH-RT) in real time. This technology aims to improve patient outcomes by accurate measurements ofin vivodose delivery to target tumor volumes.Approach. The study utilized the FLASH-capable eRT6 LINAC to deliver electron beams under various doses (1.2 Gy pulse^-1to 4.95 Gy pulse^-1) and instantaneous dose rates (1.55 × 10⁵Gy s^-1to 2.75 × 10⁶Gy s^-1), for imaging the beam in water and in a rabbit cadaver with RAI. A custom 256-element matrix ultrasound array was employed for real-time, volumetric (4D) imaging of individual pulses. This allowed for the exploration of dose linearity by varying the dose per pulse and analyzing the results through signal processing and image reconstruction in RAI.Main Results. By varying the dose per pulse through changes in source-to-surface distance, a direct correlation was established between the peak-to-peak amplitudes of pressure waves captured by the RAI system and the radiochromic film dose measurements. This correlation demonstrated dose rate linearity, including in the FLASH regime, without any saturation even at an instantaneous dose rate up to 2.75 × 10⁶Gy s^-1. Further, the use of the 2D matrix array enabled 4D tracking of FLASH electron beam dose distributions on animal tissue for the first time.Significance. This research successfully shows that 4Din vivodosimetry is feasible during FLASH-RT using a RAI system. It allows for precise spatial (∼mm) and temporal (25 frames s^-1) monitoring of individual FLASH beamlets during delivery. This advancement is crucial for the clinical translation of FLASH-RT as enhancing the accuracy of dose delivery to the target volume the safety and efficacy of radiotherapeutic procedures will be improved.

Keywords: FLASH therapy; in vivo dosimetry; radiation therapy; radiation-induced acoustic imaging (RAI).

MeSH terms

Acoustics
Animals
Electrons*
In Vivo Dosimetry / methods
Rabbits
Radiometry / methods
Radiotherapy Dosage