Toward quantitative reconstruction of delivered dose in a 3D digital water phantom for electron FLASH-RT via annular-array electron-induced acoustic imaging

Abstract

Objective. Electron FLASH radiotherapy (FLASH-RT) represents a disruptive radiotherapy modality. It enables high-dose radiation to tumor lesions over an extremely short duration, ensuring therapeutic efficacy while markedly mitigating damage to normal tissues. However, the accurate dosimetry of FLASH-RT is severely challenged under ultra-high-dose-rate (UHDR) and ultra-short-pulse conditions, where conventional ionization chambers suffer from dose saturation and spatial-averaging artifacts that fundamentally undermine their ability to resolve the delivered volumetric dose distribution. This study aims to evaluate the feasibility of quantitatively reconstructing dose distributions in electron-based FLASH-RT from multi-angle electron-induced acoustic (EA) signals in a three-dimensional (3D) digital water phantom, systematically assessing the effects of transducer configuration, the efficacy of deconvolution for signal restoration, and the depth dependence of reconstruction accuracy. Approach. We propose and validate an electron-induced acoustic imaging (EAI) reconstruction framework that synergistically integrates adaptive denoising preprocessing (via bandpass filtering and Savitzky–Golay smoothing), Wiener deconvolution for signal restoration, and time-reversal imaging for spatial mapping, to enable quantitative characterization of the delivered dose in electron-based FLASH-RT. An annular array transducer is employed to acquire time-variant acoustic matrix signals induced by UHDR pulsed electron-beam irradiation in a 3D digital water phantom; these signals serve as the input data for reconstructing the dose distribution and profiles. Comparative simulations are conducted to evaluate the influence of array transducer parameters on dose reconstruction performance, accounting for the transducer’s frequency response and the dosimetry system’s independent response characteristics. Main results. The results demonstrate that, for acoustic array signals acquired by a 128-element annular array transducer, the gamma passing rate of the dose distribution reconstructed by the proposed method was above 95% under the 5%/5 mm and 3%/3 mm criteria, and remained above 89% even under the most stringent 3%/2 mm criterion. Also, the central-profile dose curve was in good agreement with the reference dose curve, with an average dose difference of less than 6.35%. Significance. The results demonstrate the potential of this EAI-based dosimetry method for quantitative dose assessment and beam parameter characterization in electron‐based FLASH‐RT.