TRANSADVENTITIAL LOCALIZATION OF ATHEROMATOUS PLAQUES BY FLUORESCENCE EMISSION-SPECTRUM ANALYSIS OF MONO-L-ASPARTYL-CHLORIN E6

Objective: The aim was to demonstrate specific detection of the fluorescence spectra of mono-L-aspartyl chlorin e6 (NPe6) emitted from atherosclerotic arterial lesions using an extravascular approach. Methods: Cholesterol fed atherosclerotic rabbits were injected intravenously with 0.5 mg.kg-1 of NPe6. A fluorescence spectrum analysis system with a dual real time imaging system and a flexible endoscopic catheter was used. The pulsed excimer dye laser excited the photosensitiser. The fluorescence spectra were measured by a fluorescence spectrophotometer. Results: Analysis of fluorescence spectra detected from outside the adventitia showed that a fluorescence spectrum peak at 675 nm was obtained only in parts of the artery with an atheromatous plaque; however, no fluorescence could be shown in aortic segments free of atheroma. It was also noted that the intensity of the specific peak of the spectrum detected from outside a vessel was closely related to the depth of atheromatous lesions, as determined by histological analysis. An in vivo study revealed good correlation between the peak intensity (which could vary with the amount of NPe6 accumulated in the tissue) measured laparoscopically from outside the abdominal aorta and the peak intensity measured angioscopically from inside the abdominal aorta. Conclusions: It is possible to detect atheroma from outside a vessel by fluorescence spectrum analysis employing MPe6 as the robe.