Optical Coherence Tomography (OCT)
This is set-up in response to Dr. Brezinski’s June 26 editorial in Circulation.
Mark Brezinski MD, PhD is currently best known for his pioneering work with the imaging technology optical coherence tomography (OCT), where contributions range from defining physics, engineering advances, initial ‘proof of concept’ bench work, and direction of clinical trials to commercialization and FDA approval. His primary affiliations are Brigham and Women’s Hospital, Harvard Medical School, and King’s College, but significant affiliations over this period are also with Massachusetts General Hospital and Massachusetts Institute of Technology. He is also one of the co-founders of Lightlab Imaging, which is now owned by St. Jude Medical. Dr. Brezinski is the author of what many consider to be the OCT bible, “Optical Coherence Tomography: Principles and Practice”, which is now entering its second edition. But many questions on the technology arise for the interested parties, including clinicians and general non-engineers, which are easier to answer in this format. In particular, we would like to address questions related to the editorial above. This blog is intended for this purpose, particularly for cardiovascular OCT questions. Dr. Brezinski’s work in musculoskeletal OCT and quantum biology can be found elsewhere.
Dr. Brezinski’s contributions to the field of cardiovascular OCT are summarized below and will provide some background for this blog. The contributions of others are not discussed here in detail, but this is by no means meant to diminish their effort and involvement in the original birth and development of the technology. Dr. Brezinski’s textbook provides more detail on many of these investigators and their specific contributions. Examples include David Huang MD,PhD, James Fujimoto PhD, Eric Swanson MS, Joe Izatt PhD, Michael Hee MD, Gary Tearney MD, PhD, Brett Bouma PhD, Neil Weissman MD, James Southern MD, PhD, Xing de Li PhD, Christine Jesser MS, and the team at King’s College (Pa).
The greatest advantage of OCT over existing technology is its resolution, which is up to 25X higher than anything available in clinical medicine (3-15 μm), and high speed data acquisition rate (currently over 120 frames/second). Additional advantages of OCT are the small catheter/endoscope size (0.017”) and the ability to be combined with spectroscopy (particularly polarization sensitive OCT for identifying organized collagen). It is essentially imaging at the level of a biopsy, without the need for tissue removal, at acquisition rates greater than 30 frames per second.
In 1994, in search of a method for identifying the plaques that lead to most myocardial infarctions, he examined over 50 approaches. A technology known as OCT was developed for imaging cracks in fiber optics and had been applied to imaging the transparent tissue of the eye. It was based on low coherence interferometry (LCI), but the term OCT was coined in a 1991 Science article by pioneering authors including James Fujimoto PhD, David Huang MD, and Eric Swanson MS. However, at the time, it was felt that the technology could not be used in nontransparent tissue (which comprises most of the tissue in the body), so research had virtually stopped in this area and patents were relinquished. In addition, it was slow (30 seconds per image), imaging was never performed through any peripheral device (catheter, endoscope, hand held probe, etc), and the detection performance was low (signal to noise ratio under 100).
Advances attributed to Dr. Brezinski (alone or in collaboration): the first demonstration of successful OCT imaging in nontransparent tissue, which was vulnerable coronary artery plaque (Circulation 93,1206-1213, 1996), first to show that OCT imaging could be performed through a catheter (Optics Letters 21,543-545, 1996), first subcellular (level of nucleus) in vivo imaging (Proc. Natl. Acad. Sci. 94, 4256-4261, 1997), and first in vivo endoscopic-based imaging (Science 276:2037-2039, 1997) that included video rate acquisition as well as a detection sensitivity of greater than 100 decibels, which is near the quantum noise limit. He developed the OCT imaging classification system which today remains in effect (IEEE J. Select Top Quantum Electron. 5,1185-92, 1999). This paper identified that OCT showed its greatest potential in situations where biopsy could not be performed (coronary artery, cartilage, etc), in guiding microsurgical procedures (nerve repair, brain tumor resection, etc), or when biopsies have a high false negative rate (ex: Barrett’s esophagus).
He and his colleagues were the first in vivo vascular imaging (Heart 82:128-133, 1999). This work has now been extended to the intra-coronary imaging of over 10,000 patients, with regulatory approval by the FDA, as well as over 30 other countries.
Since 2000, Dr. Brezinski’s laboratory has continued to make major contributions but most will not be discussed here. Some of the most significant paradigm shifts include index matching to make blood optically transparent(Circulation. 2001; 103(15):1999), use of a parallel ultrasound beam to increase penetration (PNAS 2002; 99: 9761-9764, J.Opt.Soc.Am.A, 25, 938,2008), the development of single detector polarization sensitive OCT (PS-OCT), OCT elastography for plaque tensile strength (British J. Radiology. 2006; 79:707-11), demonstration of OCT’s ability to quantify plaque collagen (Int J Cardiol. 2006 Jan 20; [Epub ahead of print]), increasing the dynamic range of SS-OCT (J. Opt. Soc. Am. A 27, 404: 2010), and second order correlation technique for detecting lipid (Physical Review A, 78, 063824, 2008)
This blog is intended to help the general public. It is not to be a resource for business market analysis or substitute appropriate clinical use of the technology from that approved by the FDA. FDA Approved OCT Technology.
Article by Richard Frink, MD referenced in comments: Parallel Cholesterol Crystals: A Sign of Impending Plaque Rupture