Ex Vivo Assessment of Various Histological Differentiation in Human Carotid Plaque with Near-infrared Spectroscopy Using Multiple Wavelengths

Figures

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  Fig. 1.. Principle for ex vivo chemogram creation. (A) A schematic diagram of our device is shown. The sample is irradiated with specific wavelength light from the supercontinuum light source, and the near-infrared light transmitted through the sample is photographed with an infrared camera. Information, including the actual images and transmitted light, are sent to the near-infrared image analysis workstation (NIRexe). (B) Example of a chemogram using saline and oleic acid. The probability of oleic acid (orange) and saline (green) were displayed in chemogram. Target components were illustrated with the distribution mapping (right) projecting the chemogram on to the actual image (left). (C) The interest wavelengths were set to 1620, 1720, and 1910 nm. In the near-infrared spectrum of oleic acid (orange), there was a decrease in transmittance at 1720 nm. At 1910 nm, transmittance was greatly decreased in the saline spectrum (green). Chemogram was created by illustrating the relative difference compared with transmittance at 1620 nm to the color scale.

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  Fig. 2.. Near-infrared spectrums of each plaque component in carotid plaques. The near-infrared spectrums of five plaque components obtained by continuously plotting the mean transmittance were illustrated. Spectrometric measurements were performed by using VIR-9650 Fourier-transformed infrared spectrometer (Nihon Kohden Corp., Tokyo). Thin sliced sections of carotid plaques were measured in an isothermic environment at 36°C. The measured wavelengths ranged from 1200 to 2300 nm. Each measurement was made at 256 times of integration to minimize error. Based on the pathological findings, the region for measurement in each component was determined. The measurement range was set at 300 × 300 μm2.

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  Fig. 3.. Chemogram and pathological images. (A)–(C) are images distinguishing between fibrous tissue and smooth muscle. (A) Actual image acquired at 1620 nm. (B) Chemogram (green: smooth muscle, white: fibrous tissue). (C) Immunostaining of α-smooth muscle actin. (D) and (E) are images distinguishing between lipid tissue and fibrous tissue. (D) Chemogram (red: lipid tissue, yellow: fibrous tissue). (E) Oil Red O stain.

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  Fig. 4.. Chemogram and pathological images. (A) and (B) are images distinguishing between lipid tissue and intraplaque hemorrhage. (A) Chemogram (red: intraplaque hemorrhage, yellow: lipid tissue). (B) Masson trichrome stain. (C) and (D) are images focused on calcification. (A) Chemogram (black: calcification). (B) Kossa stain.