NEAR-IR IMAGING OF ATHEROMAS IN LIVING ARTERIAL TISSUE

A near-IR imaging system and parallel vector supercomputer are used wi th a fiber-optic probe to produce chemical maps of the intimal surface of living arteries. Spectrometric information collected at hundreds o f near-IR wavelengths is assembled into color pictures of the lipoprot ein and apolipoprotein composition of atheromas using a vectorized 3-D cellular automaton-based algorithm that operates in parallel. The non parametric mathematics developed to identify and quantify the constitu ents of each voxel in the artery wall avoid the matrix factorizations that generate excess error in other pattern recognition methods and pe rmit analysis in a wavelength space of over 1000 dimensions using fewe r than 100 calibration samples. A surface feature resolution of 5.5 mu m and depth resolution of 6.5 mum are achieved with the system. Data f rom the fiber optics confirm the injury hypothesis of lesion formation and the differing roles of HDL and LDL in cholesterol transport. In c linical studies, approximately 1/2 of human arterial lesions appear fi brous and contain little or no lipid. As such, these lesions would not be expected to regress in response to cholesterol-lowering agents suc h as lovastatin. Identification of lesion types in vivo will enhance t he efficacy of treatment programs.