Tisdale Katrina, Bringer Alexandra, Kiourti Asimina
Ohio State University ElectroScience Laboratory, Columbus, OH 43212 USA.
IEEE J Electromagn RF Microw Med Biol. 2022 Sep;6(3):355-363. doi: 10.1109/jerm.2021.3137962. Epub 2022 Mar 14.
This paper examines the utility of a wideband, physics-based model to determine human core body or brain temperature via microwave radiometry. Pennes's bioheat equation is applied to a six-layer human head model to generate the expected layered temperature profile during the development of a fever. The resulting temperature profile is fed into the forward electromagnetic (EM) model to determine the emitted brightness temperature at various points in time. To accurately retrieve physical temperature via radiometry, the utilized model must incorporate population variation statistics and cover a wide frequency band. The effect of human population variation on emitted brightness temperature is studied by varying the relevant thermal and EM parameters, and brightness temperature emissions are simulated from 0.1 MHz to 10 GHz. A Monte Carlo simulation combined with literature-derived statistical distributions for the thermal and EM parameters is performed to analyze population-level variation in resulting brightness temperature. Variation in thermal parameters affects the offset of the resulting brightness temperature signature, while EM parameter variation shifts the key maxima and minima of the signature. The layering of high and low permittivity layers creates these key maxima and minima via wave interference. This study is one of the first to apply a coherent model to and the first to examine the effect of population-representative variable distributions on radiometry for core temperature measurement. These results better inform the development of an on-body radiometer useful for core body temperature measurement across the human population.
本文研究了一种基于物理的宽带模型通过微波辐射测量来确定人体核心体温或脑温的效用。将彭尼斯生物热方程应用于六层人体头部模型，以生成发烧过程中预期的分层温度分布。将所得的温度分布输入到正向电磁（EM）模型中，以确定不同时间点的发射亮温度。为了通过辐射测量准确检索物理温度，所使用的模型必须纳入人群变异统计数据并覆盖较宽的频段。通过改变相关的热参数和电磁参数来研究人群变异对发射亮温度的影响，并模拟了从0.1 MHz到10 GHz的亮温度发射。进行了蒙特卡罗模拟，并结合从文献中获得的热参数和电磁参数的统计分布，以分析所得亮温度的人群水平变异。热参数的变化会影响所得亮温度特征的偏移，而电磁参数的变化会使特征的关键最大值和最小值发生偏移。高低介电常数层的分层通过波干涉产生这些关键的最大值和最小值。本研究是最早将相干模型应用于核心体温测量辐射测量的研究之一，也是最早研究具有人群代表性的变量分布对辐射测量影响的研究之一。这些结果为开发一种适用于测量全人类核心体温的人体辐射计提供了更好的参考。
