Xing Long
BME PhD Defense Presentation

Date: 2024-05-23
Time: 8:30 AM-10:30 AM(EDT, Atlanta)/ 8:30 PM-10:30 PM (Beijing)
Location / Meeting Link:

Committee Members:
Changhui Li, PhD (Advisor); Stanislav Emelianov, PhD; Peng Xi, PhD; Brooks Lindsey, PhD; Shuai Na, PhD

Title: Technical development of photoacoustic microvascular imaging

The vascular system is essential for oxygen and nutrient delivery to cells and organs while removing metabolic waste products. Among vascular network, arterioles and venules in the microvasculature act as crucial connectors between capillary networks and larger arteries and veins. Visualizing and monitoring microvessel morphology, structure, and hemodynamic changes are vital for early disease diagnosis and prognosis evaluation. However, the diameter of subcutaneous microvessels ranges from tens to more than 100 μm, and existing medical imaging techniques are not yet capable to provide high-resolution, high-contrast, noninvasive, label-free functional imaging of subcutaneous microvessels. Photoacoustic (PA) imaging (PAI) technology combines the optical contrast of light absorption with the deep penetration depth of ultrasound (US), offering promise in biomedical imaging. Compared with other vascular imaging techniques, PAI has unique advantages and demonstrates great potential for noninvasive subcutaneous microvascular imaging. However, existing PA microvascular imaging has the limitations of insufficient imaging resolution and speed for clinical applications, and conventional opaque piezoelectric transducers affect the illumination of excitation light in photoacoustic microscopy (PAM) microvascular imaging of small animals. This thesis addressed the need for high-resolution three-dimensional (3D) microvascular imaging in clinical and preclinical studies by developing various PA microvascular imaging techniques and exploring future non-contact vascular PAI methods. Key research contents and innovations include: (1) The use of a high-frequency linear array system and image processing algorithms significantly improves the speed and resolution of PA/US dual-modality imaging, enabling high-resolution rapid 3D PA/US visualization and functional quantitative imaging of human subcutaneous microvessels. (2) A wide bandwidth transparent ultrasound transducer (TUT) based on a new matching layer material and thickness design method was proposed to realize subcutaneous microvascular PAM imaging with wide bandwidth and high axial resolution. (3) A non-contact, wide bandwidth US sensing technique based on a homodyne Mach-Zehnder interferometer was developed, upon which a non-contact PAI system was built. In summary, this thesis focuses on advancing noninvasive PA microvascular imaging technology for clinical and periclinal scientific research, aiming to improve the diagnosis, treatment, and understanding of vascular-related diseases.