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

Electron FLASH radiotherapy (FLASH-RT) represents a revolutionary and disruptive radiotherapy modality. It delivers high-dose radiation to tumor lesions over an extremely short duration, ensuring therapeutic efficacy while markedly mitigating damage to healthy 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. To overcome this dosimetric bottleneck, we propose and validate an electron-induced acoustic (EA) reconstruction framework that synergistically integrates adaptive denoising regularization (via bandpass filtering and Savitzky-Golay smoothing), Wiener deconvolution for signal restoration, and time-reversal imaging for spatial mapping, enabling robust 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 three-dimensional (3D) digital water phantom, which 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. 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, indicating its promising potential for clinical dose distribution verification and beam parameter characterization in electron-based FLASH-RT.