A new publication from Opto-Electronic Advances; DOI 10.29026/oea.2022.200050 overviews pencil-beam scanning catheter for intracoronary optical coherence tomography.
Cardiovascular disease is one of the diseases that seriously threaten human health nowadays. Its morbidity and mortality have surpassed tumors. Percutaneous coronary intervention (PCI) surgery is a kind of treatment to improve myocardial blood perfusion by using catheter technologies to open narrow or closed occlusions. In PCI surgery, optical coherence tomography (OCT) becomes more and more popular for preoperative strategy formulation and postoperative effect evaluation because of OCT’s high resolution, real-time imaging speed, and label-free features.
With the promotion and application of cardiovascular OCT systems in all levels of hospitals, high performance and low-cost imaging catheters are highly demanded. Imaging catheter is the key part of intravascular OCT system and the catheter is disposable in practice. The performance of imaging catheter determines the success or failure of PCI surgery, and imaging catheter’s production cost affects the application range of cardiovascular OCT technology.
Technically, the imaging catheter consists of meters of single-mode fiber (SMF) to guide near infrared light at 1310-nm band in general and a distal focusing optics to focus the light beam onto lesions. In current mainstream gradient-index (GRIN) lens probe, a glass rod spacer is set before a GRIN lens to expand light beam for desired beam profile. This design provides great flexibility to control beam profile. However, it has several shortcomings. Firstly, the length of the glass rod spacer with several hundred micrometers is crucial and should be well controlled which is difficult to manipulate in practice. Secondly, since the light beam is expanded before GRIN lens, it is hard to fabricate small size catheters by a small GRIN lens. A large size GRIN lens is hard to be fusion spliced directly with conventional SMF and UV curing might be applied. Finally, the complicated structure increases the fabrication cost and thus set an obstacle for mass production. Consequently, how to design and fabricate a type of imaging catheter with high performance, simple architecture, and low cost is an interesting topic.
To fulfill these requirements, the research group of Associate Professor Yunxu Sun from Harbin Institute of Technology (Shenzhen) cooperates with the research group of Professor Kenneth K. Y. Wong from The University of Hong Kong and Shenzhen Vivolight Medical Device & Technology Co., Ltd. to develop a type of novel all-fiber imaging catheter for intravascular OCT application.
In this novel design, the GRIN lens was fusion spliced directly with ~1.6-m SMF, and 185-μm long no-core fiber (NCF) was fusion spliced with the GRIN fiber. NCF provides a polishing basement to make a 40-degree angle reflection surface at the tip of the probe for side-viewing. This non-45-degree angle design aims to diminish the specular reflection from the sheath and sample surfaces. After polishing, the probe was enclosed into a double-wrapped torque coil which was used to uniformly transfer torque from proximal to distal end during rotation and to linearly translate the probe. The highest rotation speed of the torque coil can achieve 12,000 rpm. The probe and the coil were bonded together by UV adhesive, and a piece of heat-shrink tubing was used to protect the polished facet and to enclose some air at the same time for total internal reflection. To isolate the rotary probe from body fluids and to spin the catheter for circumferential cross-sectional imaging, a 0.86 mm diameter plastic sheath with a transparent imaging window at the distal end was used to encase the torque coil and distal optics.
The imaging capability of the catheter was proved in vivo in a 4‑month‑old domestic porcine who was anesthetized first for the in vivo intracoronary imaging as shown in Fig. 1(a) and 1(b). The intracoronary images captured by this spacer-removed catheter are shown in Fig. 1(c) to 1(e), where Fig. 1(c) and 1(d) are the cross-section images of the blood vessel without and with stent attachment, respectively. Fig. 1(e) is cutaway view of the 3D image of a segment of coronary artery with stent and guide wire.
These results prove the effectiveness of this type of catheter in intravascular OCT imaging application. Currently, this design is put into mass production in Shenzhen Vivolight Medical Device & Technology company, Shenzhen, China.
Article reference: Kang JQ, Zhu R, Sun YX, Li JN, Wong KKY. Pencil-beam scanning catheter for intracoronary optical coherence tomography. Opto-Electron Adv 5, 200050 (2022). doi: 10.29026/oea.2022.200050
Keywords: optical coherence tomography / endoscopic imaging / intravascular imaging / fiber optics imaging
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Yunxu Sun received his BS in physics from Beijing University of Technology, China, in 2000 and received his PhD degree in Physics from Tsinghua University in 2006. He is currently an associate professor in the School of Electronics and Information Engineering at Harbin Institute of Technology, Shenzhen (HITsz). Dr. Sun is also a team member of Laser Information Technology Research Team (LITRT) in HITsz. LITRT belongs to the National Key Laboratory of Science and Technology on Tunable Laser in HIT. LITRT currently has more than 12 researchers, 4 postdoctoral fellow, and more than 40 graduate students. The research directions of LITRT include but not limited to special fiber design and fiber sensing, nonlinear optics, fiber laser, and silicon-based photonics, etc.
Kenneth K. Y. Wong received his BE (1st class honor with medal award) degree in electrical engineering and BS degree in physics from The University of Queensland, Australia, in 1997. He received his MS in 1998 and PhD degree in 2003, both in electrical engineering at Stanford University. He is currently a professor in the Department of Electrical and Electronic Engineering at The University of Hong Kong and Advanced Biomedical Instrumentation Centre in Hong Kong Science Park. His research includes fiber nonlinearity, fiber optical parametric amplifiers, microwave photonics, and biophotonics. Professor Wong’s group has published more than 100 papers in high-level journals, such as Nature Communication, Light: Science & Applications, Optica, Optics Letters, and Optics Express, etc.
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