A new approach to obtaining a high-resolution picture of the interior of a coronary artery could dramatically reduce the time required for imaging, making it safer and easier for doctors to check stents for stability and keep track of new scar tissue.
According to an article published April 7 in Technology Review, two U.S. companies, LightLab of Westford, Mass., and Austin-based CardioSpectra, are working individually on a scanning method that would take a fraction of the time, greatly reducing the risk of damage to the heart. The new method builds on an old technique called optical coherence tomography (OCT).
OCT works by projecting a beam of light onto a surface, which then reflects a small amount of light back to the device. Due to the high speed at which light travels, reflection time is too brief to be measured directly. Instead, OCT relies on an interferometer, which measures the interference of noncoherent light. Because the light waves have a short wavelength, high-resolution images can be generated.
Technology Review reported that the imaging technique is occasionally used to scan coronary arteries, however it cannot see through blood, which requires any area being scanned to be flushed with saline. During the procedure, a special balloon is used to block incoming blood, which can cause damage to the tissue.
CardioSpectra, recently acquired by intravascular ultrasound (IVUS) manufacturer Volcano, is working on improving OCT using the Fourier domain, a mathematical formula used to process a complex signal so that it can be differentiated into its component parts and analyzed. Such an improvement means that multiple wavelengths of data can be gathered simultaneously rather than sequentially, substantially reducing the scanning time, according to Technology Review.
Traditional OCT scanning requires multiple exposures of light aimed at specific points to make a full image. Fourier domain OCT exposes the entire area at once, reducing the time required to obtain a section from 30 seconds to two seconds. This reduction dramatically reduces the associated risks of the procedure. In two seconds, an area of artery 40 mm to 50 mm in size can be scanned, with an accompanying improvement in scanning resolution down to 10 microns, Technology Review reported.
Even though the basis of the Fourier domain OCT was conceived more than four years ago, the technological advances that make it practical are comparatively recent. Fourier domain OCT requires three important pieces of equipment: the scanning laser, the processing electronics, and the light detectors, according to Chris Peterson, vice president of research and development at LightLab.
An initial application for this technology will be to image stents after insertion to ensure they haven't shifted. According to Technology Review, research from Harvard University Medical School has shown that stent prolapsing can occur with shifts of less than 100 microns, a level that would go undetected by IVUS.
The increased accuracy of OCT technology allows doctors to observe how well the stent is adhering to the arterial walls and to track small amounts of endothelial regrowth that would go unnoticed by IVUS. It could also be used postoperatively to check healing. The resolution of this scan is fine enough to allow doctors to identify small but significant plaque deposits that existing technology might overlook. The technology could also be used to carefully target biopsies, as cancerous cells could be identified in much smaller quantities than currently possible, reported Technology Review.