High-resolution three-dimensional quantitative photoacoustic and ultrasound imaging of subcutaneous microvasculature in extremities

Visualizing and monitoring morphological and functional information of microvasculature, including arterioles and venules, plays a crucial role in assessing vascular-related diseases. Clinical angiography methods have limitations in observing small peripheral microvessels down to 100 μm. Here, this study achieved three-dimensional (3D) non-invasive imaging of the subcutaneous microvascular network and monitored hemodynamic change by using an ultrasound (US)/photoacoustic (PA) dual-modality imaging system. Not only were the microvasculature and subcutaneous tissues in the extremities visualized with high resolution, but also the quantitative oxygen saturation (sO₂) of microvessels was measured. To monitor the hemodynamic change in microvasculature, vascular occlusion was performed to simulate vascular-related disease, and successfully measured multiple parameters, such as average PA amplitude, oxygenated hemoglobin (HbO₂), deoxygenated hemoglobin (Hb), and sO₂, during normal perfusion, vascular occlusion, and reperfusion processes, respectively. Based on the preliminary results, the high-frequency 3D US/PA dual-modality imaging shows great potential in early diagnosis and therapeutic monitoring of microvascular-related diseases.