On Application of IR and NIR Fiber Optic Imaging in Thermographic and Spectroscopic Diagnosis of Atherosclerotic Vulnerable Plaques: Preliminary Experience

摘要

Despite major advances in cardiovascular science and technology during the past three decades, approximately half of all myocardial infarctions and sudden deaths occur unexpectedly. It is widely accepted that coronary atherosclerotic plaques and thrombotic complications resulting from their rupture or erosion are the underlying causes of this major health problem. The majority of these vulnerable plaques exhibit active inflammation, a large necrotic lipid core, a thin fibrous cap, and confer a stenosis of less than 70%. These lesions are not detectable by stress testing or coronary angiography~(1,2,3). Our group is exploring the possibility of a "functional classification" based on physiological variables such as plaque temperature, pH, oxygen consumption, lactate production etc. We have shown that heat accurately locates the inflamed plaques. We also demonstrated human atherosclerotic plaques are heterogeneous with regard to pH and hot plaques and are more likely to be acidic. To develop a non-surgical method for locating the inflamed plaques, we are developing both IR fiber optic imaging and NIR spectroscopic systems in our laboratory to detect hot and acidic plaque in atherosclerotic arterial walls. The system comprises: 1) the IR 180 degree 1 mm window side-viewing fiber optic imaging bundle made of 19 (coaxial) individual As_2S_3 chalcogenide 100 micron glass fibers which transmit infrared radiation from 0.7 μm with attenuation rate of <0.5 db/m and coupled with a cooled infrared focal plane array (FPA) detector. We are able to obtain the real time thermal map of the vessel wall in situ; 2) the NIR 360 degrees 0.5 mm window side-viewing silica fiber optic bundle (600-2500 microns) made of 39 (coaxial) fibers, 13 illuminating and 26 receiving fibers coupled through two SMA connectors to a spectrometer. Preliminary NIR spectra collected with this and another custom probe distinguished different gross pathology and underlying histopathologic features of plaque. Our findings introduce the possibility of an isolated/combined IR and NIR fiber optic catheter that can bring new insight into functional assessment of atherosclerotic plaque and thereby detection of active and inflamed lesions responsible for heart attacks and strokes.