3D real-time ultrasound/photoacoustic anatomical/functional imaging platform for hemodynamic response assessment: A feasibility study

The hemodynamic response is a critical physiological indicator for assessing cardiopulmonary function and monitoring therapeutic efficacy in various diseases. Photoacoustic imaging (PAI), which combines the strengths of ultrasound and optical imaging, has emerged as a prominent noninvasive, non-ionizing modality for monitoring and evaluating hemodynamic responses. However, conventional Q-switched laser-based PAI systems, which are typically used for deep-tissue imaging at several centimeters beneath the skin, face inherent limitations due to the trade-off between pulse repetition frequency (PRF) and laser energy. These constraints hinder real-time performance and restrict imaging to primarily 2D cross-sectional views.In this study, we propose a 3D ultrasound/photoacoustic imaging platform that integrates an OPO-based DPSS laser system with a 2D matrix array transducer for hemodynamic response assessment. The platform employs customized multi-wavelength sequences to perform volumetric imaging and spectral unmixing, thereby enabling the evaluation of distinct optical components. To validate the system, we conducted phantom experiments simulating vascular structures. Through spectral unmixing analysis regarding two mixed inks (cyan & magenta), the platform displayed a cyan ink concentration ratio map based on the inks' different optical absorption properties, demonstrating its functional imaging capability. Furthermore, real-time performance was confirmed by recording ink flow at 30 frames per second.The proposed system shows strong potential as a contrast-free vascular and hemodynamic imaging platform for both preclinical and clinical applications, and future studies will investigate its clinical feasibility in greater depth.