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Trends in Photochemistry & Photobiology   Volumes    Volume 10 
Abstract
Observation of fluorescent image and spectra for the processing of pathological changes in arteries using photosensitizer
Junichi Hayashi, Katsuo Aizawa, Takashi Saito
Pages: 57 - 65
Number of pages: 9
Trends in Photochemistry & Photobiology
Volume 10 

Copyright © 2003 Research Trends. All rights reserved

ABSTRACT
 
The photosensitizer, mono-L-aspartyl chlorin e6 (Talaporfin), specifically accumulates in atheromatous plaque.  We detected the fluorescence spectra emitted from atheromatous plaques in the descending thoracic aorta by angioscope using the Epifluorescence image analyzer system with an atheroscleraotic rabbit.

The structure of mono-L-aspartyl chlorin e6 tetra sodium salt tetra hydrate (Talaporfin) is a compound with a molecular weight of 799.69.

Absorbance spectrum of Talaporfin has a characteristic Soret band at a wavelength of 400nm and Q bands at four wavelengths at 502, 530, 602 and 654nm in PBS solution pH7.2.  Fluorescence spectrum curves are obtained by excitation at 400nm, with a peak, appearing at a wavelength of 660 nm.  There was spectra red shift of about 10 nm on binding with pathological areas.

We developed an epifluorescence image analyzer system consist of a stereoscope, an epifluorescence microscope, a video monitoring system and a diode laser system.  For diode laser system we selected a 405 nm wavelength using a band passed filter for exciting the Talaporfin.

Fluorescence micrographs of the coronary artery excised from an atherosclerotic rabbit heart 6 hours after Talaporfin (5 mg/kg body weight) administration to a cholesterol-fed rabbit using an excitation wavelength at 405 nm.  Branching parts of the coronary artery and small coronary artery were highly illuminated, indicating the presence of thick atheroma at 672 nm.

The vascular endoscope epifluorescence spectra analysis system included an excimer pulse dye laser, a fluorescence spectrum analysis system, a dual real time imaging system and an endoscopic catheter 2.1 mm in diameter.

The endoscopic image pattern and the fluorescence spectral pattern within the 600-750 nm by excitation at 405 nm could be displayed simultaneously on the same monitor.

Clearest angioscopic focusing was obtained at a distance of 6 mm from the tip of the angioscope to the target tissue.

Fluorescence intensity of Talaporfin was measured on both the adventitia sides and intima sides of the celiac artery branch point of the aorta in an atherosclerotic rabbits.

There was a high correlation coefficient (r=0.976, p<0.01) between the relative units of accumulated Talaporfin obtained from adventitia and intima simultaneously.

The maximum depth of the lesion highly correlated with the fluorescence peak intensity of the atheroma specific spectrum at 672 nm obtained from the adventitia of the excised aorta.

There was a high correlation coefficient (r=0.976, p<0.01) between the peak fluorescence intensity expressed in relative units and maximum thickness of atheroma.  The number of measurements was 6 in each of 5 rabbits in the vascular endoscope group. Our findings suggest that photodynamic diagnosis with Talaporfin on the atheromatous plaque could be an effective clinical approach to regress atherosclerosis lesion.

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