Researchers at Massachusetts General Hospital have developed a new method, called optical frequency-domain imaging (OFDI), to visualize plaque deposits within coronary arteries.
OFDI is an advance over optical coherence tomography (OCT), another imaging technology developed by the MGH investigators. While OCT examines tissues one point at a time, OFDI can look at over 1,000 points simultaneously using a device developed at MGH-Wellman. Inside a fiberoptic probe, a constantly rotating laser tip emits a light beam with an ever-changing wavelength. As the probe moves through the structure to be imaged, measuring how each wavelength is reflected back allows rapid acquisition of the data required to create the detailed microscopic images. Besides providing three-dimensional images of an artery’s microstructure in seconds, the increased speed also reduces signal interference from blood, which had plagued the first-generation technology. In 2006 members of the MGH-Wellman team reported the successful use of OFDI to image the esophagus and coronary arteries of pigs.
The current study enrolled three patients scheduled to have stents placed in their coronary arteries at the Lahey Clinic in Burlington, Mass. After the completion of stent placement, OFDI was used to image 3- to 7-centimeter-long segments of the patients’ coronary arteries including the stented areas. OFDI provided detailed images along the length of the arteries – visualizing lipid or calcium deposits, immune cells that could indicate inflammation, and the stents – and dramatic “fly-through” views looking down the artery’s interior. More detailed, cross-sectional images of narrowed vascular segments revealed features associated with the type of atherosclerotic plaques that are likely to rupture and cause a heart attack.
Tearney and his colleagues note that these findings need to be duplicated in a larger group of patients, and the time required to process the “fly-through” images – currently several hours – needs to be reduced to provide the real-time information most useful for clinical applications. Combining OFDI with intravascular ultrasound might help with another of the technique’s limitations, the inability to penetrate deep into tissues.
Press release: Technology gives three-dimensional view of human coronary arteries …
Images: Top: OFDI fly-through view of patient’s right coronary artery, white arrowheads indicate area of lipid deposits at white dotted line in image above. Side: Cutaway OFDI image of a portion of same patient’s right coronary artery, showing newly placed drug-eleuting stent (dark blue), macrophages (green) and lipid deposits (yellow).