Optical coherence tomography characterizes arterial plaque

Optical coherence tomography, a light-based imaging strategy, was found to compare favorably with intravascular ultrasound and to nearly match histopathology in determining the structure of atherosclerotic plaques in a study presented Saturday.

The study was based on 50 segments obtained from five amputated limbs. It found that OCT delivered sensitivity and specificity scores of 81% and 89% for fibrous plaques, 100% and 93% for lipid-rich plaques, and 80% and 89% for calcified plaques, respectively. Quantitative measurements showed a high correlation with intravascular ultrasound, the reference standard for intravascular imaging, said presenter Dr. Oliver Meissner of the University of Munich.

The OCT technique is similar to IVUS. But instead of acoustical waves, it uses infrared laser light to image the vessel wall. OCT is capable of a 10-fold higher resolution over IVUS, to about 50 microns, according to Meissner.

A catheter with the imaging device inside a silicone sheath is inserted into the vessel, accompanied by a saline flush under pressure. At the tip of the catheter is a rotating prism that directs light on the walls of the vessels to create cross-sectional images, Meissner said. The process acquires about 35 images per second.

Meissner showed comparisons of histologically proven diseased and disease-free vessels that revealed different parts of the vessel walls. One diseased segment showed vessel wall distortion and dark zones representing calcifications. Other pathologies have higher signal strengths, with lipid-rich plaques showing medium intensity without sharp borders, and fibrous plaque showing a bright signal.

When compared with IVUS in quantitative measures, OCT underestimated the lumen by 2% and plaque area measurements by 4%, Meisnner said.

One drawback, he acknowledged, is that the procedure can block circulation, but this can be largely overcome with the saline flush technique. New developments in the works will speed up the image acquisitions so that an OCT scan will cover 10 cm in less than five seconds.

The technique has had CE approval in Europe since April. FDA approval in the U.S. is expected in the middle of this year, Meissner said.