Intravascular Photoacoustic (IVPA) imaging is a promising new technology to assess lipid content of coronary atherosclerotic plaque, an important determinant of the risk associated with the plaque triggering a heart attack. Clinical translation of IVPA imaging requires real-time image acquisition, which has been a technological challenge. In this work, we demonstrate a high-speed, dual-wavelength IVPA imaging system at 1.7 µm wavelength, operating with a flexible catheter of 1.2 mm outer diameter (including outer sheath). The catheter was custom designed and fabricated, and used a 40 MHz transducer for intravascular ultrasound (IVUS) and IVPA imaging. The optical excitation is provided by a dual OPO system, pumped by CW diode-pumped Q-switched Nd:YAG lasers, with a repetition rate of 5 kHz. Each OPO can be tuned to a custom wavelength between 1690 and 1750 nm; two wavelengths only are needed to discriminate between plaque lipids and adipose tissue. The pulse energy is about 80 µJ. We tested the imaging performance of the presented system in a polyvinyl-alcohol (PVA) vessel mimicking phantom and human coronary arteries ex vivo. IVPA identified lipid deposits inside atherosclerotic plaque, while IVUS showed tissue structure. We demonstrated IVPA imaging at a speed of 20 frames per second, with 250 A-scans per frame. This is significantly faster than previous IVPA imaging systems, and will enable the translation of IVPA imaging into clinical practice.
Min Wu, Verya Daeichin, Geert Springeling, Antonius F. W. van der Steen, and Gijs van Soest, "Lipid detection by intravascular photoacoustic imaging with flexible catheter at 20 fps (Conference Presentation)," Proc. SPIE 9689, Photonic Therapeutics and Diagnostics XII, 968931 (Presented at SPIE BiOS: February 14, 2016; Published: 27 April 2016); https://doi.org/10.1117/12.2212846.4828143245001.
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