Optical Coherence Tomography

ince intravascular ultrasound (IVUS) was introduced in the early 1990 s,1,2 it has been used not only as an adjunctive device to percutaneous coronary interventions (PCI), but also as a research tool to evaluate vessel structure in detail. Although IVUS has helped broaden our understanding of coronary artery structure, its limited spatial resolution does not allow for the assessment of microstructures, which is important for identification of vulnerable plaques. Optical coherence tomography (OCT) is analogous to ultrasound, except that it generates images by measuring the echo time delay and magnitude of backscattered light instead of sound.3 OCT was developed by Huang et al at the Massachusetts Institute of Technology and demonstrated for ex vivo imaging of the retina and atherosclerotic plaque in 1991.3 A related concept to OCT was also independently proposed by Tanno et al in Japan in 1991.4 OCT enables “optical biopsy”, imaging tissue structure and pathology in situ and in real time. It has become a standard imaging modality in clinical ophthalmology, where it is used for the diagnosis of retinal disease, assessing disease progression and response to therapy.5 The possibility of using OCT intravascularly was first suggested in 1996 by Brezinski et al in an ex vivo imaging study that demonstrated the ability of OCT to resolve the thin intimal cap layers that are associated with unstable plaques.6 A prototype OCT imaging catheter using fiber optics was developed and demonstrated for imaging vascular structure ex vivo,7 as well as for in vivo endoscopic imaging in animals.8 In 1998 we established the first cardiac OCT research group at the Massachusetts General Hospital (MGH) to explore the clinical applications of OCT. In this review we will summarize the steps taken to bring this technology from bench to bedside over the past 15 years.