ABSTRACT
INTRODUCTION Optical coherence tomography (OCT) is a novel optical imaging technology that provides cross-sectional tomographic imaging for biomedical structure with great spatial resolution.1
The principle of OCT is similar to that of intravascular ultrasound (IVUS) except OCT utilizes near-infrared wavelength light instead of sound waves. The typical OCT image has a homoaxial resolution of 10 m and a lateral resolution of 20 m, which is 10 times higher than that of IVUS. This increased resolution, however, comes at the expense of tissue penetration. The absorption and scattering of light by biologic tissues limit OCT to a depth of ≤2 mm in endovascular tissue.2 Yet, due to the enhanced resolution, OCT is able to detect subtle differences, which the conventional IVUS cannot depict. Endovascular images are scanned using a fiber-optic scanning catheter-endoscope. The current commercially available catheter consists of a singlemode optical fiber in a hollow rotating or translating cable that emits and scans the OCT beam radially from the catheter axis.2 The diameter of the wire with transducer is as small as 0.014 in. Current imaging systems require proximal balloon occlusion and flush administration during image acquisition with an automated pullback speed of 1 mm/sec and creation of approximately 16 cross-sectional frames per millimeter. This level of dense longitudinal imaging coupled with incredible resolution makes OCT ideal for evaluation of vascular biology as well as the response of vascular wall to injury or device implantation. This section will focus on the clinical application of OCT and the analysis of images obtained by the most commercially available motorized pullback OCT image wire system (M2 OCT system and ImageWire, LightLab Imaging Inc., Westford, MA).
