Seeing the invisible: In vivo dosimetry in radiotherapy with radiacoustic imaging

Radiation therapy is a cornerstone of cancer management, utilized in over half of all cancer treatments. Treatment precision is critical for ensuring the efficacy of radiation therapy. Current radiotherapy modalities-x-ray photon, proton, and electron therapies-each offer distinct advantages and challenges depending on tumor characteristics and treatment goals. Despite technological advancements in treatment planning and image guidance, challenges such as intra-fractional and inter-fractional tumor motion and the lack of in vivo dose verification persist. Radiacoustic imaging (RAI) has emerged as a promising solution for real-time in vivo dose verification and adaptive radiotherapy. By detecting acoustic waves generated during radiation dose deposition, RAI offers the potential to enhance treatment precision and outcomes. This review explores the development, performance, and clinical applications of RAI, particularly its utility across photon, proton, and electron therapies, as well as its potential in FLASH radiotherapy. We also discuss its future prospects, projecting its integration into clinical workflows and its role in transforming cancer treatment.