A collinear catheter for label-free intravascular photoacoustic imaging was developed with a diameter of 1.6 mm. The collinear overlap between optical and acoustic waves enabled photoacoustic imaging of a human coronary artery from lumen to perivascular fat

Cao, Yingchun

Chen, Weibiao

Cheng, Ji-Xin

Hui, Jie

Kole, Ayeeshik

Sturek, Michael

Wang, Pu

Yingchun Cao

Jie Hui

Ayeeshik Kole

Pu Wang

Weibiao Chen

Michael Sturek

Ji-Xin Cheng

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Highly Sensitive Intravascular Photoacoustic Imaging with a Collinear Catheter Probe

Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences

IUPUIScholarWorks

ATh4N.4.pdf CLEO:2016 © OSA 2016Highly Sensitive Intravascular Photoacoustic Imaging with a Collinear Catheter Probe Yingchun Cao1, Jie Hui2, Ayeeshik Kole1,3, Pu Wang1, Weibiao Chen4, Michael Sturek1,3 and Ji-Xin Cheng1,5,* 1Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA 2Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA 3Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA 4Key Laboratory of Space Laser Communication and Detection Technology, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China 5Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA * jcheng@purdue.eduAbstract: A collinear catheter for label-free intravascular photoacoustic imaging was developed with a diameter of 1.6 mm. The collinear overlap between optical and acoustic waves enabled photoacoustic imaging of a human coronary artery from lumen to perivascular fat. OCIS codes: (110.5120) Photoacoustic imaging; (120.4570) Optical design of instruments. 1. IntroductionAtherosclerosis is the major form of cardiovascular disease, the No. 1 cause of death in the developed countries during the past century [1]. As an emerging tool, intravascular photoacoustic (IVPA) imaging provides sufficient imaging depth and chemical information to identify the vulnerable plaques [2]. Recently reported IVPA imaging systems were largely based on cross overlap between the illumination light beam and ultrasound detection, which had limited imaging depth. A coaxial IVPA catheter based on a ring transducer allowed good overlap of sound wave and photons, but had a relatively large diameter that needs to be further reduced to meet the clinical requirements [3]. Here, we report a novel IVPA catheter based on collinear alignment of the optical and acoustic waves, which allows IVPA imaging over 6 mm depth. High-quality imaging of a human coronary artery from lumen to perivascular fat is demonstrated. 2. Design and fabrication of the IVPA catheterThe schematic design of the catheter is shown in Fig. 1. A multimode fiber with one end polished to 45° was used to deliver the excitation laser beam forward. An ultrasonic transducer parallel to the fiber with its sensing area facing the polished fiber plane was served to detect the generated photoacoustic wave collinear with the excitation beam. The transducer also performed ultrasound imaging through the same trace with a proper delay. A 1-mm-diameter rod mirror reflects both the optical and acoustic waves to the perpendicular direction for cross-sectional imaging. These components were installed in a 3D printed housing. A photo of the lab-fabricated collinear catheter is displayed in Fig. 1(d), showing a probe diameter of 1.6 mm. Fig. 1. Schematic of the collinear catheter probe. (a) Main components of the probe, (b) assembled catheter probe structure, (c) Zoom-in view of the catheter tip, (d) a photo of the fabricated catheter probe with a diameter of 1.6 mm. 3. Characterization of spatial resolutionThe spatial resolution of our IVPA imaging system is measured with a 7-µm carbon fiber. IVPA images of the carbon fiber were obtained at different axial distances as shown in Fig. 2(a). Axial and lateral resolutions at these ___________________________________________________________________This is the author's manuscript of the article published in final edited form as:Cao, Y., Hui, J., Kole, A., Wang, P., Chen, W., Sturek, M., & Cheng, J. X. (2016, June). Highly sensitive intravascular photoacoustic imaging with a collinear catheter probe. In CLEO: Applications and Technology (pp. ATh4N-4). Optical Society of America. https://doi.org/10.1364/CLEO_AT.2016.ATh4N.4ATh4N.4.pdf CLEO:2016 © OSA 2016positions were obtained with a Gaussian fit of the photoacoustic signal at the carbon fiber position and plotted in Fig. 2(b). Relatively constant values of 80 µm and 400 µm for axial and lateral resolutions are observed. The amplitude of photoacoustic signals at these axial positions exhibits an exponential decay. The signal at 6.2 mm axial distance can be clearly distinguished, indicating an imaging depth over 6 mm for our imaging system.  Fig. 2. Performance of the IVPA catheter. (a) IVPA image of the 7-µm carbon fiber, (b) measured axial and lateral resolutions and (c) photoacoustic amplitude of the carbon fiber at different axial positions.  4.  Intravascular imaging of a human coronary artery ex vivo After validated for lipid absorption with a lab-built optical parametric oscillator at 1.7 µm [4], our imaging system was carried out for intravascular imaging of a fresh human coronary artery ex vivo at an imaging speed of 1 frame per second. To provide complementary information, intravascular ultrasound (IVUS) was performed simultaneously for the artery with the embedded transducer. The imaging results are shown in Fig. 3. The lumen size and vessel structure can be visualized from IVUS (Fig. 3(b)), while IVPA image reveals lipid depositions in the arterial wall, as well as outside the vessel boundary as perivascular fat with an axial distance ~4.3 mm.   Fig. 3. Registered IVPA/IVUS image of a human coronary artery. (a) IVPA image, (b) IVUS image, and (c) merged result. 5. Conclusion We developed and fabricated an IVPA catheter with a collinear overlap between the optical and acoustic waves. An imaging depth over 6 mm was achieved with this design by using a 7-µm carbon fiber as a target. Our imaging system was performed for co-registered IVPA/IVUS imaging of a human coronary artery, resulting in the ability of visualizing the entire arterial wall, from lumen to perivascular fat. Our collinear catheter design greatly improved the performance of an IVPA imaging system with extended imaging depth and higher sensitivity, which fastens the realization of in vivo IVPA imaging in clinic. 6. References  [1] A. S. Go, D. Mozaffarian, V. L. Roger, et al., “Heart Disease and Stroke Statistics-2014 Update A Report From the American Heart Association,” Circulation 129, E28-E292 (2014).  [2] K. Jansen, A. F. W. van der Steen, H. M. M. van Beusekom, J. W. Oosterhuis, and G. van Soest, “Intravascular photoacoustic imaging of human coronary atherosclerosis,” Opt. Lett. 36, 597-599 (2011).  [3] P. Wang, T. Ma, M. N. Slipchenko, et al., "High-speed intravascular photoacoustic imaging of lipid-laden atherosclerotic plaque enabled by a 2-kHz barium nitrite raman laser," Sci. Rep. 4, 6889 (2014).  [4] J. Hui, Q. Yu, T. Ma, et al., “High-speed intravascular photoacoustic imaging at 1.7 µm with a KTP-based OPO,” Biomed. Opt. Express 6, 4557-4566 (2015). 

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Highly Sensitive Intravascular Photoacoustic Imaging with a Collinear Catheter Probe

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Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences

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