Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea.
Department of Digital Media Communication Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea.
Biosensors (Basel). 2023 Jul 5;13(7):711. doi: 10.3390/bios13070711.
In this study, we demonstrated a Monte Carlo simulation to model a finger structure and to calculate the intensity of photons passing through tissues, in order to determine optimal angular separation between a photodetector (PD) and a light-emitting diode (LED), to detect SpO. Furthermore, our model was used to suggest a mirror-coated ring-type pulse oximeter to improve the sensitivity by up to 80% and improve power consumption by up to 65% compared to the mirror-uncoated structure. A ring-type pulse oximeter (RPO) is widely used to detect photoplethysmography (PPG) signals for SpO measurement during sleep and health-status monitoring. Device sensitivity and the power consumption of an RPO, which are key performance indicators, vary greatly with the geometrical arrangement of PD and LED within the inner surface of an RPO. We propose a reflection-boosted design of an RPO to achieve both high sensitivity and low power consumption, and determine an optimal configuration of a PD and LED by performing a 3D Monte Carlo simulation and confirming its agreement with experimental measurement. In order to confirm the reflection-boosted performance in terms of signal-to-noise ratio, R ratio, and perfusion index (PI), RPOs were fabricated with and without a highly reflective coating, and then used for SpO measurement from eight participants. Our simulation allows the numerical calculation of the intensity of photon passing and scattering through finger tissues. The reflection-boosted RPO enables reliable measurement with high sensitivity, resulting in less power consumption for the LED and longer device usage than conventional RPOs without any reflective coating, in order to maintain the same level of SNR and PI. Compared to the non-reflective reference RPO, the reflection-boosted RPO design greatly enhanced both detected light intensity (67% in dc and 322% in ac signals at a wavelength = 660 nm, and also 81% and 375% at = 940 nm, respectively) and PI (23.3% at and 25.5% at ). Thus, the reflection-boosted design not only enhanced measurement reliability but also significantly improved power consumption, i.e., by requiring only 36% and 30% power to drive the LED sources with and , respectively, to produce the device performance of a non-reflective RPO reference. It is expected that our proposed RPO provides long-term monitoring capability with low power consumption and an enhanced PI for SpO measurement.
在这项研究中，我们进行了蒙特卡罗模拟，以模拟手指结构并计算光子穿过组织的强度，从而确定光电探测器 (PD) 和发光二极管 (LED) 之间的最佳角度分离，以检测 SpO。此外，我们的模型被用于建议一种涂有反射镜的环形脉搏血氧仪，以提高 80%的灵敏度并将功耗降低 65%，与未涂反射镜的结构相比。环形脉搏血氧仪 (RPO) 广泛用于在睡眠和健康状态监测期间检测用于 SpO 测量的光容积描记图 (PPG) 信号。设备灵敏度和 RPO 的功耗是关键性能指标，这两个指标都随 RPO 内表面上 PD 和 LED 的几何排列而有很大差异。我们提出了一种反射增强型 RPO 设计，以实现高灵敏度和低功耗，并通过执行 3D 蒙特卡罗模拟来确定 PD 和 LED 的最佳配置，并通过实验测量来确认其一致性。为了确认信噪比、R 比和灌注指数 (PI) 方面的反射增强性能，我们制造了带有和不带有高反射涂层的 RPO，并随后使用它们从八名参与者那里进行 SpO 测量。我们的模拟允许对光子穿过手指组织并散射的强度进行数值计算。反射增强型 RPO 能够实现可靠的高灵敏度测量，从而与没有任何反射涂层的传统 RPO 相比，LED 的功耗更低，设备的使用寿命更长，以保持相同的 SNR 和 PI 水平。与非反射参考 RPO 相比，反射增强型 RPO 设计大大提高了检测光强度（在波长 = 660nm 时，直流为 67%，交流为 322%，在波长 = 940nm 时，直流为 81%，交流为 375%）和 PI（在 时为 23.3%，在 时为 25.5%）。因此，反射增强设计不仅提高了测量的可靠性，而且还显著改善了功耗，即，分别仅需要 36%和 30%的功率来驱动 和 的 LED 源，以产生非反射 RPO 参考的器件性能。预计我们提出的 RPO 将提供具有低功耗和增强的 PI 的长期监测能力，用于 SpO 测量。
