Performance comparison of high-speed photoacoustic microscopy: opto-ultrasound combiner versus ring-shaped ultrasound transducer

Hyojin Kim; Jin Young Kim; Seonghee Cho; Joongho Ahn; Yeonggeun Kim; Hyungham Kim; Chulhong Kim

doi:10.1007/s13534-022-00218-y

Performance comparison of high-speed photoacoustic microscopy: opto-ultrasound combiner versus ring-shaped ultrasound transducer

Biomed Eng Lett. 2022 Mar 2;12(2):147-153. doi: 10.1007/s13534-022-00218-y. eCollection 2022 May.

Authors

Hyojin Kim^#¹, Jin Young Kim^#¹, Seonghee Cho¹, Joongho Ahn¹, Yeonggeun Kim¹, Hyungham Kim¹, Chulhong Kim¹

Affiliation

¹ Departments of Electrical Engineering, Convergence IT Engineering, Mechanical Engineering, and Interdisciplinary Bioscience and Bioengineering, Medical Device Innovation Center, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang, Gyeongbuk 37673 Republic of Korea.

^# Contributed equally.

Abstract

Photoacoustic microscopy (PAM) embedded with a 532 nm pulse laser is widely used to visualize the microvascular structures in both small animals and humans in vivo. An opto-ultrasound combiner (OUC) is often utilized in high-speed PAM to confocally align the optical and acoustic beams to improve the system's sensitivity. However, acoustic impedance mismatch in the OUC results in little improvement in the sensitivity. Alternatively, a ring-shaped ultrasound transducer (RUT) can also accomplish the confocal configuration. Here, we compare the performance of OUC and RUT modules through ultrasound pulse-echo tests and PA imaging experiments. The signal-to-noise ratios (SNRs) of the RUT-based system were 15 dB, 12 dB, and 7 dB higher when compared to the OUC-based system for ultrasound pulse-echo test, PA phantom imaging test, and PA in-vivo imaging test, respectively. In addition, the RUT-based system could image the microvascular structures of small parts of a mouse body in a few seconds with minimal loss in SNR. Thus, with increased sensitivity, improved image details, and fast image acquisition, we believe the RUT-based systems could play a significant role in the design of future fast-PAM systems.

Keywords: Opto-ultrasound combiner; Performance comparison; Photoacoustic microscopy; Ring-shaped ultrasound transducer; Sensitivity; Signal-to-noise ratio.