Endoscopic Optical Coherence Tomography System Research

Endoscopic optical coherence tomography can achieve high resolution in vivo imaging of human internal organs and tissues, which offers a powerful tool for early diagnosis of serious diseases and image guide of particularly complex surgical procedures.The designation and fabrication of a miniaturized high-performance probe are critical for E-OCT. A tapered structure based all-fiber endoscopic OCT probe was presented in this paper. Compared to the conventional fiber-lens structure based endoscopic probe, the all-fiber probe has a prominent edge in size and flexibility. Due to its lower beam-divergence, the large core multi-mode fiber makes a better fit than a general single mode fiber when utilized to replace the micro lens in a conventional endoscopic probe as the imaging component. Furthermore, a tapered fiber was introduced as a transition section between the single mode fiber and the large core multi-mode fiber in order to enhance the light transmission efficiency and reduce the rigid length of the probe simultaneously. First, in order to obtain an optimal performance, optical simulation software Rsoft was adopted to determine the probe's proper lengths of the tapered section and the large core multimode fiber. Second, the all-fiber structure based endoscopic probe was fabricated by tapering, cutting and fusing processes. The beam characterization and insertion loss of the fabricated probe were measured experimentally. The probe itself is 250?m, after covering with a stainless steel protective tube, its outer diameter becomes 325?m. The rigid length of the probe is about 1 cm which is more flexible and easier for inserting into curved blood vessels. The insertion loss of the probe is measured to be about 0.3 dB. To the best of our knowledge, it is the lowest among all the all-fiber endoscopic probes. Finally, the probe was integrated with a custom-built swept-source optical coherence tomography system. Imaging of human fingertip and ex-vivo chicken trachea was conducted to demonstrate the key performance parameters of our probe. The effective imaging range of the probe is up to 800 microns in air without the help of any extra mechanism to expand its depth of focus. The probe offers a compact, efficient and flexible candidate for endoscopic optical coherence tomography, which is promising in biomedical imaging.In addition, a preliminary study of integrated intravascular ultrasound-OCT endoscopic imaging system was conducted for early diagnosis of atherosclerosis vulnerable plaques. The universal design principle of endoscopic OCT probe was discussed firstly. A kind of "back-to-back" proximal actuated integrated endoscopic probe was then proposed on this basis. In addition, a design of large-size integrated probe which is distal actuated by magnetic mechanism was presented and demonstrated by making use of our home-made swept source OCT system.