A live demonstration of a next-generation optical coherence tomography (OCT) system from LightLab Imaging (Westford, MA) drew rave reviews from a crowd of more than 1000 interventional cardiologists attending the Transcatheter Cardiovascular Therapeutics (TFT) conference in Washington D.C. last October. Performed in Germany by Prof. Dr. Eberhard Grube of the Helios Heart Center (Siegburg, Germany) and beamed live to the main hall of the Washington Convention Center, the procedure provided real-time OCT images of a recently implanted stent and the tissues covering the stent struts with a resolution of 15 to 20 µm—more than 10 times the resolution of intravascular ultrasound (IVUS), the dominant intracoronary imaging technology these days (see figure). The images were provided by LightLab’s next-generation spectral-domain scanning-laser OCT system (SL-OCT).
According to Gregg Stone, M.D., professor of medicine at Columbia University and chairman of the Cardiovascular Research Foundation (CRF), which sponsors the TFT meeting, many in the crowd were “amazed” at the OCT images. Gary Mintz, chief medical officer of the CRF, said it was the most excitement he’d seen at the meeting in recent years.
“The difference in resolution between OCT and IVUS is extraordinary,” Dr. Stone says. “This should significantly improve our ability to make accurate decisions for patients.”
The 1300 nm LightLab SL-OCT device is based on the fundamental Fourier-domain modelocking technology developed at the Massachusetts Institute of Technology (Cambridge, MA) by James Fujimoto (see related story, p. 20). LightLab’s first-generation system, the M2 OCT, is a time-domain OCT system. Compared to the M2 system, the SL-OCT system is much faster and provides higher-resolution, higher-quality images, according to Joe Schmitt, chief technology officer at LightLab. The SL-OCT system collects about 45,000 lines/s at 100 frames/s, compared to the M2, which collects about 4800 lines/s at 15 frames/s. In addition, the SL-OCT system takes a different approach to resolving a fundamental issue in cardiovascular applications: OCT cannot image in blood because the components of red blood cells cause diffuse reflection of near-infrared light.
“Our earlier generation of this product (the M2) uses an occlusion balloon to briefly stop the blood flow while doing OCT imaging in the arteries,” Schmitt says. “With the new system we are using a rapid-flush method that is auto-triggered. When you press the syringe (to deliver the saline), image acquisition begins. The catheter begins to spin, the sheath moves back, and you end up with a full spiral scan. Because you can pull back about 20 mm/s, you only need two to three seconds to cover the entire image area.”
The SL-OCT system possesses a higher sensitivity than the M2 system and its resolution is approximately three times higher, he adds, allowing for even more detailed intravascular observation and paving the way to 3-D intravascular imaging. Potential applications in clinical diagnostics include improved diagnosis of vulnerable plaques, identification of the presence of thrombus following coronary stent treatment and image diagnosis that helps to decide endpoints for the treatment of incomplete stent apposition, and auxiliary diagnosis for determining the period to discontinue antiplatelet therapy in drug-eluting stent patients.
The market potential for OCT imaging in cardiology is significant; currently, IVUS is a $400 million market with only 14% market penetration, according to Volcano (San Diego, CA), a leading provider of IVUS technologies. Given that OCT offers 10 times the resolution of IVUS, the future looks quite bright indeed for companies like LightLab Imaging and even Volcano. In mid-December Volcano announced that it will pay $25 million to acquire CardioSpectra (San Antonio, TX), a small company founded to commercialize OCT technology developed at the University of Texas (see related story, p. 14).
The LightLab SL-OCT system is in preclinical trials. The company is preparing to begin U.S. clinical trials and hopes to launch the system commercially by the end of 2008.
“Five years ago, intravascular imaging was a $150 million to $200 million market,” Schmitt says. “Now it is double that because of stents. But ultrasound doesn’t have enough resolution to image the thrombosis that can occur with stents. So our OCT product is quite timely.” —KK