Photoacoustic–ultrasound multimodal method for monitoring tissue thermal damage during photothermal therapy

Photothermal therapy (PTT) is an emerging minimally invasive cancer treatment that eradicates tumor cells through localized heating induced by near-infrared (NIR) laser irradiation. Its advantages—such as high spatial selectivity and reduced side effects—make PTT a promising modality in clinical oncology. However, the therapeutic efficacy of PTT critically depends on accurate temperature control during irradiation. Excessive heating may harm adjacent healthy tissues, while insufficient heating can leave residual tumor cells, both of which compromise treatment outcomes and patient safety. To address this, real-time monitoring of thermal damage within target tissues is essential. Conventional thermometry techniques—including infrared thermography and invasive thermocouples—are limited by shallow penetration, invasiveness, or poor spatial resolution. In this study, we present a novel photoacoustic–ultrasound (PA–US) multimodal approach for intraoperative monitoring of tissue thermal injury. By simultaneously tracking changes in photoacoustic and ultrasound signals during laser irradiation, our method enables real-time, label-free identification of thermally damaged regions with high spatial and temporal resolution. This integrated imaging strategy offers a promising solution for precise thermal control during PTT and has potential for broader applications in thermal therapy monitoring.