Du Le V N, Wang Quanzeng, Gould Taylor, Ramella-Roman Jessica C, Pfefer T Joshua
Appl Opt. 2014 Jun 20;53(18):4061-71. doi: 10.1364/AO.53.004061.
Narrow-band imaging (NBI) is a spectrally selective reflectance imaging technique that is used clinically for enhancing visualization of superficial vasculature and has shown promise for applications such as early endoscopic detection of gastrointestinal neoplasia. We have studied the effect of vessel geometry and illumination wavelength on vascular contrast using idealized geometries in order to more quantitatively understand NBI and broadband or white light imaging of mucosal tissue. Simulations were performed using a three-dimensional, voxel-based Monte Carlo model incorporating discrete vessels. In all cases, either 415 or 540 nm illumination produced higher contrast than white light, yet white light did not always produce the lowest contrast. White light produced the lowest contrast for small vessels and intermediate contrast for large vessels (diameter≥100 μm) at deep regions (vessel depth≥200 μm). The results show that 415 nm illuminations provided superior contrast for smaller vessels at shallow depths while 540 nm provided superior contrast for larger vessels in deep regions. Besides 540 nm, our studies also indicate the potential of other wavelengths to achieve high contrast of large vessels at deep regions. Simulation results indicate the importance of three key mechanisms in determining spectral variations in contrast: intravascular hemoglobin (Hb) absorption in the vessel of interest, diffuse Hb absorption from collateral vasculature, and bulk tissue scattering. Measurements of NBI contrast in turbid phantoms incorporating 0.1-mm-diameter hemoglobin-filled capillary tubes indicated good agreement with modeling results. These results provide quantitative insights into light-tissue interactions and the effect of device and tissue properties on NBI performance.
窄带成像（NBI）是一种光谱选择性反射成像技术，临床上用于增强浅表血管系统的可视化，并且在诸如胃肠道肿瘤的早期内镜检测等应用中显示出前景。我们使用理想化的几何形状研究了血管几何形状和照明波长对血管对比度的影响，以便更定量地理解NBI以及黏膜组织的宽带或白光成像。使用包含离散血管的基于体素的三维蒙特卡罗模型进行了模拟。在所有情况下，415或540nm照明产生的对比度均高于白光，但白光并不总是产生最低的对比度。对于小血管，白光产生的对比度最低；对于深部区域（血管深度≥200μm）直径≥100μm的大血管，白光产生中等对比度。结果表明，415nm照明在浅深度为较小血管提供了更好的对比度，而540nm照明在深部区域为较大血管提供了更好的对比度。除了540nm，我们的研究还表明其他波长在深部区域实现大血管高对比度的潜力。模拟结果表明了三个关键机制在决定对比度光谱变化中的重要性：感兴趣血管内的血管内血红蛋白（Hb）吸收、来自侧支血管系统的漫射Hb吸收以及大块组织散射。在包含直径0.1mm的充满血红蛋白的毛细管的浑浊模型中对NBI对比度的测量表明与建模结果吻合良好。这些结果为光与组织的相互作用以及设备和组织特性对NBI性能的影响提供了定量见解。
