This Small Business Innovation Research (SBIR) Phase I project seeks to demonstrate that 840 nm spectral domain optical coherence tomography (OCT) can provide images equal to or better than those currently available from swept source OCT, with the added advantages of higher imaging speeds and lower cost. Intravascular OCT is poised for commercial growth, but is still limited by technical complexity, availability, and cost. This Phase I SBIR proposes a complete prototype system based on a very high resolution (0.02 nm/pixel) spectrometer, capable of imaging 5 mm deep with a resolution of < 10 microns. A novel fiber probe will be designed and prototyped. Proof of principle data will be collected from tissue phantoms and waste animal tissue. Pending successful completion of a Phase I, a Phase II project would complete system engineering, decrease system cost, and target first in-human imaging.
The broader impact/commercial potential of this project is an increase in performance and availability of intravascular OCT (IV-OCT). Intravascular OCT provides detailed imaging information for plaque assessment, stent implantation, and stent monitoring over time. Identification and treatment of unstable plaques and other intravascular conditions can reduce the morbidity and mortality rate from coronary artery disease (CAD). CAD is the primary cause of heart attacks and strokes, which killed over 631,000 and 137,000 people, respectively, in the U.S in 2006. The market size for intravascular OCT is estimated at more than $1B annually, but there is currently only one commercially available IV-OCT system. By increasing system speed and reducing cost, this project will accelerate clinical use of IV-OCT.
." PI: William J. Brown, PhD Date: September 7, 2012 This report covers the progress made through June 30, 2012 on our Phase I and Phase Ib SBIR’s, "High-speed Low-cost Spectral Domain Optical Coherence Tomography System for Intravascular Imaging Applications". Summary of Phase I Proposal We proposed to design and build a proof-of-principle 840 nm spectral domain optical coherence tomography (OCT) imaging system for high speed intravascular imaging. Compared to existing swept source imaging systems, the innovation in our system will increase imaging speed and resolution while reducing system cost and complexity. Intravascular OCT provides detailed imaging information for plaque assessment, stent implantation, and stent monitoring over time. Identification and treatment of unstable plaques and other intravascular conditions can reduce the morbidity and mortality rate from coronary artery disease (CAD). CAD is the primary cause of heart attacks and strokes which killed over 631,000 and 137,000 people, respectively, in the U.S in 2006. Current standard of care for imaging arterial vessels is intravascular ultrasound (IVUS). IVUS has an axial resolution that is limited to 100 microns with a radial imaging depth of 7 mm. This provides sufficient depth to image the outer wall of the blood vessel, but does not have sufficient resolution to measure the thickness of the fibrous caps over the plaques (referred to as thin-cap fibroantheroma or TCFA) and to image stents either at the time of placement or at a subsequent date. The TCFA has been shown to be an important predictor of the likelihood of rupture, and together with thickness measurements, provide valuable, diagnostic information. A better approach to intravascular imaging is provided by intravascular optical coherence tomography (IV-OCT). Current systems, based on swept source technology at 1310 nm, provide an axial resolution of 15 microns, with a radial imaging depth of 5 millimeters. With this level of resolution, fibrous caps can be seen and their thickness quantitated. Likewise stents can be assessed at time of placement and later at follow up. We propose building an 840 nm spectral domain IV-OCT system. In contrast to existing systems, our design uses 840 nm light instead of 1310 nm light and utilizes spectral domain OCT instead of the swept source OCT. Swept source OCT uses a laser where the wavelength is changed in time (swept) thereby interrogating the tissue with different wavelengths of light. Return signals are sequentially captured by a detector and then processed to generate OCT A-scans and radial images. Spectral domain OCT uses a broadband superluminescent diode (SLD) that generates light across the entire bandwidth of wavelengths covered by a swept source and captures the returned light on a spectrometer where individual wavelengths are simultaneously recorded across an array of detectors. Spectral domain OCT and swept source OCT have been shown to have the same optical signal-to-noise properties even though the implementations are different. During the Phase I/Ib we completed the following work: - We have designed and built an OCT engine operating at 840 nm with sufficient imaging depth for intravascular OCT and better axial resolution than existing systems. - Costs have been reduced by building our own camera for the OCT spectrometer based on a CMOS line scan array. Combined with readily available superluminescent diodes, the cost of the OCT engine are in line with expectations and below currently available swept source laser systems. - Initial imaging on porcine tissue supports the thesis that 840 nm OCT works as well as 1310 nm OCT for intravascular imaging. - Prototype fiber probe has been designed, built and tested. - Motorized pullback stage for fiber probe has been designed, built and tested. - We performed head to head comparison between 840 nm and 1310 nm OCT using a tissue phantom. Comparison images are provided.
