Annu Int Conf IEEE Eng Med Biol Soc. 2022 Jul;2022:850-853. doi: 10.1109/EMBC48229.2022.9871922.
This paper presents a multilayer Monte Carlo model of a healthy human neck to investigate the light-tissue interaction during different perfusion states within its dermal layer. Whilst there is great interest in advancing wearable technologies for medical applications, and non-invasive techniques like photoplethysmography (PPG) have been studied in detail, research has focused on more conventional body regions like the finger, wrist, and ear. Alternatively, the neck could offer access to additional physiological parameters which other body regions are unsuitable for. The aim of this work was to investigate the effects of several factors that would influence the optimum design of a reflectance PPG sensor for the neck. These included the source-detector separation on the optical path, penetration depth, and light detection efficiency. The results were generated from a static multilayer model in a reflectance mode geometry at two wavelengths, 660 nm and 880 nm, containing different blood volume fractions with a fixed oxygen saturation. Simulations indicated that both wavelengths penetrated similar depths, where optimal source-detector separation should not exceed 3 mm or 2.4 mm, for red and infrared respectively. Within this range, light interrogates the dermal-fat boundary corresponding to the last neck tissue layer positively contributing to a neck PPG acquisition.
本文提出了一个健康人体颈部的多层蒙特卡罗模型，以研究其真皮层在不同灌注状态下的光组织相互作用。虽然人们对开发用于医疗应用的可穿戴技术非常感兴趣，并且已经详细研究了光电容积描记法（PPG）等非侵入性技术，但研究重点主要集中在手指、手腕和耳朵等更传统的身体部位。相比之下，颈部可以提供其他身体部位不适合的额外生理参数。这项工作的目的是研究几个因素对颈部反射式 PPG 传感器的最佳设计的影响。这些因素包括光路中的源探测器分离、穿透深度和光检测效率。结果是在反射模式几何形状下的静态多层模型中生成的，波长分别为 660nm 和 880nm，包含固定氧饱和度的不同血液体积分数。模拟表明，两种波长穿透的深度相似，红光的最佳源探测器分离不应超过 3mm，红外光的最佳源探测器分离不应超过 2.4mm。在这个范围内，光会探测到对应于最后一个颈部组织层的真皮脂肪边界，这对颈部 PPG 采集有积极贡献。
