Endoscopic micro-optical coherence tomography using imaging probe with extended depth of focus for three-dimensional intravascular imaging

Abstract

Cardiovascular disease is one of the leading cause of death and investigating the wall of the coronary arteries is very important for diagnosing this disease. Intracoronary optical coherence tomography (IV-OCT) is widely used in clinical fields because it enables imaging of three dimensional structures of the vessel wall with high spatial resolution up to 10μm. In general, it has a limitation to visualize cellular or sub-cellular structures because of its insufficient spatial resolution. Therefore, in order to overcome the limit of spatial resolution of OCT, micro OCT has been developed to improve the spatial resolution of OCT up to 1μm using a broadband light source. However, there are difficulties in developing endoscopic micro OCT for coronary artery imaging. Due to the use of a broadband light source, it is difficult to develop the optical rotary joint required for three dimensional imaging. In addition, miniaturization of imaging probe and having a sufficient imaging range are difficult due to the use of high numerical aperture lens. In this paper, I have overcome these difficulties and developed an endoscopic micro OCT that can be inserted into a blood vessel using 1 mm diameter optics with binary phase spatial filter, and confirmed that three-dimensional imaging is possible. As a result of the performance verification using microspheres, the system has axial and lateral resolution of 2.46μm and 2.59μm, respectively. And the sensitivity of the system is 90.03dB. The imaging range is improved by 1.91 times using BPSF. And also, three-dimensional images of various blood vessel model of animal were acquired using this endoscopic µ-OCT ex vivo. These images demonstrate clear visualization of the cellular features observed in normal and plaque lesion of the blood vessel and stent healing process not seen with conventional IV-OCT. I anticipate that the endoscopic µ-OCT system can be useful for clinical and preliminary studies of various diseases. In order to utilize the developed endoscopic micro OCT for in vivo studies, it is necessary to further miniaturize the imaging probe and acquire statistical analysis of the detected microstructure to increase the reliability of the data. However, this study showed sufficient feasibility to observe the microstructures of the coronary artery. Therefore I anticipate that the endoscopic micro OCT system will be a useful tool for clinical and preliminary studies.