Atherosclerosis is a primary cause of critical ischemic diseases like heart infarction or stroke. A method that can provide detailed information about the stability of atherosclerotic plaques is required. We focused on spectroscopic techniques that could evaluate the chemical composition of lipid in plaques. A novel angioscope using multispectral imaging at wavelengths around 1200 nm for quantitative evaluation of atherosclerotic plaques was developed. The angioscope consists of a halogen lamp, an indium gallium arsenide (InGaAs) camera, 3 optical band pass filters transmitting wavelengths of 1150, 1200, and 1300 nm, an image fiber having 0.7 mm outer diameter, and an irradiation fiber which consists of 7 multimode fibers. Atherosclerotic plaque phantoms with 100, 60, 20 vol.% of lipid were prepared and measured by the multispectral angioscope. The acquired datasets were processed by spectral angle mapper (SAM) method. As a result, simulated plaque areas in atherosclerotic plaque phantoms that could not be detected by an angioscopic visible image could be clearly enhanced. In addition, quantitative evaluation of atherosclerotic plaque phantoms based on the lipid volume fractions was performed up to 20 vol.%. These results show the potential of a multispectral angioscope at wavelengths around 1200 nm for quantitative evaluation of the stability of atherosclerotic plaques.
Spectroscopic techniques have been researched for intravascular diagnostic imaging of atherosclerotic plaque. Nearinfrared
(NIR) light efficiently penetrates of biological tissues, and the NIR region contains the characteristic absorption
range of lipid-rich plaques. The objective of this study is to observe atherosclerotic plaque using a NIR multispectral
angioscopic imaging. Atherosclerotic plaque phantoms were prepared using a biological tissue model and bovine fat. For
the study, we developed an NIR multispectral angioscopic imaging system with a halogen light, mercury-cadmiumtelluride
camera, band-pass filters and an image fiber. Apparent spectral absorbance was obtained at three wavelengths,
1150, 1200 and 1300 nm. Multispectral images of the phantom were constructed using the spectral angle mapper
algorithm. As a result, the lipid area, which was difficult to observe in a visible image, could be clearly observed in a
multispectral image. Our results show that image-enhanced observation and quantification of atherosclerotic plaque by
NIR multispectral imaging at wavelengths around 1200 nm is a promising angioscopic technique with the potential to
identify lipid-rich plaques.
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