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. 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 nonsurgical 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. 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.
For some twenty plus years, infrared glasses have been one of the coming new materials. They have always had a lot of promise but, except for some military applications of bulk components, infrared glasses have not been commercialized. There is now a new wave of attempted commercialization with groups in France, and the USA building embryonic businesses in heavy metal fluoride fibers, and groups in Japan, USA, and Russia beginning to develop marketable chalcogenide fiber. Some work is also being done with modeled chalcogenide glass lenses. The major applications for the fiber are chemical sensing (spectroscopy), temperature sensing (pyrometry), and low-level laser power delivery. Telecommunications and long lengths of ultra-low loss fiber are not a significant factor in today's market, indeed the loss requirements for most applications are in the 100s of dB/km. Even at those levels, however, heroic efforts of raw material purification are often required to obtain the necessary properties. All infrared glasses have characteristics that make them more difficult to work with than conventional glasses. Against this is the advantage that these materials, to a greater or lesser extent, transmit in the infrared region of the spectrum and may be used to make fibers or optical components with characteristics that are otherwise not available.
Instrument accessories for remote infrared spectroscopy have been developed employing chalcogenide fiber. The fiber probes, designed for immersion in standard laboratory hardware, provide scientists with new possibilities for acquiring spectral signatures between 3400 cm-1 and 850 cm-1 for quantitative analysis of a wide variety of solutions, mixtures, sludge, mud, creams, and gels, including biological samples.
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