Optical coherence tomography (OCT) is a noninvasive, noncontact imaging modality that uses coherent gating to obtain high-resolution cross-sectional images of the microstructure of biological tissues. Recently, OCT has been considered as a promising technique for intravascular imaging, since it provides direct visualization of vessel walls with resolutions of 1-2 orders higher than intravascular ultrasound (IVUS). However, there are two major drawbacks for OCT: limited penetration depth makes it difficult to image the whole depth of atherosclerotic plaques and clearance of blood is required since the presence of blood can seriously attenuate OCT signals. OCT and ultrasound (US) are complementary in the application of intravascular imaging.

This research focuses on the development of an integrated OCT-US system for the application of intravascular imaging. By combining the two imaging modalities, the system is capable of offering simultaneous OCT and ultrasound images in real-time, thus allowing for images with both high resolution and a deep imaging depth which will significantly improve diagnostic accuracy in the detection of atherosclerosis. OCT-US probes that combine OCT optical components and US transducers have been developed. Different probe designs have been realized based on different applications; and the latest version of the miniature design aimed at human coronary artery imaging has a maximum outer diameter of only 0.69mm. A rotary joint that combines a fiber optic rotary joint and electrical slip ring has been developed, so that both optical and electrical signals can be transmitted between the stationary and rotary parts of the system. The integrated imaging system provides real-time simultaneous OCT and US data acquisition, processing and image display by using a single two-channel data acquisition board and a home-developed OCT-US program. In vitro human coronary specimen imaging and in vivo animal studies have been performed to demonstrate the feasibility of our OCT-US system in the application of intravascular imaging.

Last but not least, a 3-dimensional high speed endoscopic OCT system has been developed for the application of airway imaging. In vivo animal studies of smoke-induced early airway injury were performed using this system. Image processing software has been successfully developed for motion artifact removal, image reconstruction and quantitative analysis of airway thickness.