Voitovich Daria, Kurnikov Alexey, Orlova Anna, Petushkov Aleksej, Shimolina Liubov, Komarova Anastasia, Shirmanova Marina, Liu Yu-Hang, Razansky Daniel, Subochev Pavel
Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov Str., Nizhny Novgorod 603950, Russia.
Institute of Experimental Oncology and Biomedical Technologies, Privolzhsky Research Medical University, Nizhny Novgorod 603005, Russia.
Photoacoustics. 2025 May 29;44:100734. doi: 10.1016/j.pacs.2025.100734. eCollection 2025 Aug.
Optical-resolution optoacoustic (photoacoustic) microscopy is a hybrid imaging modality combining focused optical excitation with ultrasound detection, thus achieving micrometer-scale spatial resolution and high-contrast angiographic imaging. Despite these important advantages, maintaining safe laser fluence levels is essential to prevent tissue damage while ensuring sufficient detection sensitivity. Here, we introduce a model that directly relates the detector's noise-equivalent pressure (NEP) to the local laser fluence at the imaged blood vessel. The model incorporates acoustic propagation effects from an optoacoustic source to a spherically focused detector with limited aperture and bandwidth, offering a more comprehensive understanding of how fluence and ultrasonic sensitivity are interconnected. The effects of ultrasound generation propagation and detection were accounted for using analytical estimations and numerical simulations, while detector's NEP was experimentally measured with a calibrated hydrophone. The proposed model for evaluating of local laser fluence with a calibrated ultrasound detector was validated through in vitro experiments with superficially located blood layer and numerical Monte Carlo/k-Wave simulations featuring deeper vessels. In vivo experiments employing 532 nm laser excitation and wideband 1-30 MHz ultrasonic detection further demonstrated the model's capacity for real-time adjustments of laser parameters to ensure tissue safety.
光学分辨率光声显微镜是一种将聚焦光学激发与超声检测相结合的混合成像模式，从而实现微米级空间分辨率和高对比度血管造影成像。尽管具有这些重要优势，但在确保足够检测灵敏度的同时，维持安全的激光能量密度水平对于防止组织损伤至关重要。在此，我们引入一个模型，该模型直接将探测器的噪声等效压力（NEP）与成像血管处的局部激光能量密度相关联。该模型纳入了从光声源到具有有限孔径和带宽的球形聚焦探测器的声传播效应，能更全面地理解能量密度与超声灵敏度是如何相互关联的。利用解析估计和数值模拟考虑了超声产生、传播和检测的影响，同时使用校准水听器对探测器的NEP进行了实验测量。通过对浅表血层进行体外实验以及对深部血管进行数值蒙特卡罗/k波模拟，验证了所提出的使用校准超声探测器评估局部激光能量密度的模型。采用532 nm激光激发和1 - 30 MHz宽带超声检测的体内实验进一步证明了该模型实时调整激光参数以确保组织安全的能力。
