A near infrared angioscope visualizing lipid within arterial vessel wall based on multi-spectral image in 1.7 μm wavelength band

摘要

We have developed a near infrared (NIR) angioscope that takes multi-wavelength images in 1.7μm band for visualizing lipid-rich coronary plaques. The angioscope comprises light source, camera, and angioscopic catheter. The light source, containing a supercontinuum source and a switching optical filter, emits 1.60, 1.65, 1.73 and 1.76μm wavelengths sequentially in synchronization to the camera frame. The supercontinuum is seeded by 1.55μm wavelength pulses, whose spectrum is spread by an optical fiber with ring loops for reducing peak power so that light in 1.7μm band is generated efficiently. The switching filter contains 1×4 fiber-optic path switches and interferometric band-pass filters. The camera detects NIR images by an InGaAs/GaAsSb type-II quantum well sensor at 100 frames/s. The source wavelength and the camera frame are synchronized with each other by an FPGA. The angioscopic catheter, based on a silica-based image-guide designed for 1.7 μm wavelength, transmits 1300-pixel NIR images and has 0.73 mm outer diameter, which is compatible with the conventional angioscope and suited for continuous flushing to displace blood. We have also developed image processing software that calculates spectral contribution of lipid as lipid score at each pixel and create lipid-enhanced color images at 12 frames/s. The system also includes conventional visible light source and camera, and takes visible light images synchronously with the lipid-enhanced images. The performance of the angioscope for detecting lipid-rich plaque has been verified in bench tests using a plaque model made by injecting lard into excised swine carotid arterial vessel. The plaque models are imaged in water at working distances of 0 to 2 mm, and significantly distinguished from normal vessels.