Surgical planning and intraoperative assessment depend on both vascular architecture and hemodynamics. The three-dimensional organization of vessel networks defines tissue perfusion boundaries, while real-time flow changes indicate vessel patency, ischemic risk, and postoperative functional recovery. Photoacoustic angiography combines optical absorption contrast with ultrasonic detection, enabling high-sensitivity and high-resolution visualization of superficial microvasculature. However, high-resolution photoacoustic angiography is typically limited by a small single-scan field of view, while freehand scanning is vulnerable to respiration, heartbeat, tissue deformation, bleeding, and hand motion. Existing two-dimensional stitching methods can expand the field of view, but they often lose depth information and cannot readily preserve flow velocity and direction.
In a new paper accepted for publication in Light: Science & Applications , a team of scientists led by Professor Sihua Yang from the MOE Key Laboratory of Laser Life Science and the School of Optoelectronic Science and Engineering, South China Normal University developed a real-time photoacoustic angiography tracking and mapping strategy called PAATAM, which turns photoacoustic vascular images into intrinsic cues for freehand localization and mapping. The method extracts vascular geometry from three-dimensional point clouds and absorption-related texture from intensity projection images. These two complementary features are integrated with cross-validation, motion distortion correction, and sliding-window factor graph optimization to estimate the six-degree-of-freedom motion of a handheld probe and reconstruct globally consistent panoramic three-dimensional vascular maps.
The scientists summarize the operational principle of PAATAM as follows:
“We establish a vascular hybrid-feature-driven localization and mapping method for freehand photoacoustic angiography. Continuously acquired photoacoustic data are reconstructed into vascular point clouds, intensity images, and depth images, which are used for real-time probe pose estimation and panoramic three-dimensional mapping.”
“By coordinating vascular geometry and signal-intensity features, the method reduces registration degradation and accumulated drift caused by tissue motion, bleeding, low-texture regions, and hand tremor. This enables robust three-dimensional vascular mapping on complex curved organs,” they added.
The method was validated in human oral imaging and rat partial gastrectomy model. In the surgical experiment, PAATAM rapidly generated a preoperative three-dimensional vascular navigation map of the gastric region, revealing the spatial relationship between the resection area and vessels to be preserved. Postoperative scanning further enabled evaluation of major vessel preservation. Combined with photoacoustic optical-flow analysis, the method also captured flow velocity and direction, reflecting hemodynamic changes during vascular occlusion and reperfusion.
The reported strategy provides an integrated structural and functional imaging basis for surgical vascular navigation, perfusion assessment, and postoperative functional evaluation. It may open new avenues for real-time, freehand, and minimally invasive photoacoustic imaging in future surgical guidance.
Light: Science & Applications
Robust hybrid feature-driven on-the-fly mapping enables freehand 3D panoramic photoacoustic angiography