High-speed handheld photoacoustic microscopic probe through high-frequency transparent ultrasound transducer and fiber scanner

Optical resolution photoacoustic microscopy (OR-PAM) has been applied in various biomedical application with its ability to provide high-resolution, depth-resolved, and agent-free images of microvasculature. Handheld OR-PAM which can extend its applicability has been developed. However, it remains a challenge to achieve compactness, high imaging speed, and high performance at the same time. Previous works often sacrificed one or more of these aspects. This study presents a novel handheld OR-PAM probe that addresses these limitations by integrating a fiber scanner and a high-frequency transparent ultrasound transducer (TUT). The fiber scanner enables rapid C-scan imaging, and the use of TUT eliminates acoustic losses associated with beam combiners, allowing the implementation of a high-frequency transducer. Our system achieves a compact design with a probe diameter of 17 mm and a rigid body length of 90 mm, while offering lateral and axial resolutions of 7 μm and 47 μm, respectively. It can acquire C-scan volume with a 2.6 mm field of view in diameter within 1.5 seconds. These were validated through in-vivo experiments on small animals. The probe's adaptability was shown by imaging various abdominal organs through minimally invasive procedures. This work offers a promising solution for practical biomedical applications, combining compactness, speed, and high-resolution imaging. Its usability makes it suitable for a wide range of clinical and research applications, including dermatology and intraoperative imaging, potentially enhancing diagnostic and monitoring accuracy in various medical fields.