Mechanisms Underlying Millimeter Wave Therapy

描述（由申请人提供）：毫米波（MW）已被证明可以产生生物效应，并被用于医学治疗。由于渗透较浅，毫米波主要与皮肤结构相互作用。人们普遍认为，由于温度升高和升温速率高，10毫瓦/平方厘米或更高强度的照射能够对生物物质产生热效应。后一个因素可能在刺激皮肤神经末梢方面发挥重要作用。最近的理论分析表明，由于热噪声，在低于10 MW /cm2的暴露强度下，MW在分子和细胞水平上的直接相互作用不会影响生物系统。因此，为了确定毫瓦生物效应的机制，定量表征皮肤内不同点的功率密度和吸收，以及皮肤热敏结构位置的温度升高和加热速率是非常重要的。由于毫瓦的波长与皮肤层的厚度相当，因此毫瓦的频率依赖吸收在不同的层之间是不同的。皮肤的非均匀结构，如血管和汗管，会干扰附近区域的能量密度。因此，本研究旨在确定皮肤不同层和非均质附属物内毫瓦能量沉积的频率依赖性。利用多层组织模型，从理论上和实验上研究不同暴露条件下皮肤的微波加热以及血液流动和水分蒸发对温度升高的影响。我们还将检查MW引起皮肤局部血管扩张的能力。一些剂量学方法，如比吸收率测量，广泛用于量化整个射频频谱的吸收能量，但不适用于浅穿透毫瓦频率，在应用于毫瓦频率时应加以修正。在我们的研究中开发的测定毫瓦能量沉积和皮肤加热的新方法将用于建立适当的剂量学。拟议项目的结果将用于评估MW与皮肤结构相互作用的生物物理机制，并用于改进中心其他项目动物研究中的剂量学。

DESCRIPTION (provided by applicant): Millimeter waves (MW) have been shown to produce biological effects and are being used for medical treatment. Due to shallow penetration, MW interact primarily with the skin structures. It was accepted that exposures at intensities of 10 mW/cm2 and higher were able to produce thermal effects on biological substances due to temperature elevation and a high heating rate. The latter factor could play an important role in stimulating nerve endings in the skin. Recent theoretical analyses showed that due to thermal noise, the direct interaction of MW on molecular and cellular levels at exposure intensities less than 10 mW/cm2 could not affect biological systems. Hence, to identify the mechanisms of biological effects of MW, it is very important to characterize quantitatively the power density and absorption at different points within the skin, and the temperature elevations and heating rates in the locations of thermosensitive structures of the skin. As the wavelength of MW is comparable with the thicknesses of skin layers, the frequency-dependent absorption of MW differs for layers. Non-homogeneous structures of the skin such as blood vessels and sweat ducts can disturb the power density in nearby areas. Thus, the present studies are designed to determine the frequency dependence of the MW energy deposition within different layers and non-homogenous appendages of the skin. Using multilayer tissue models, we will investigate theoretically and experimentally the MW heating of the skin under different exposure conditions and effect of blood flow and water evaporation on the temperature elevation. We will also examine the capability of MW to elicit local vasodilatation in the skin. Some dosimetry methods such as specific absorption rate measurements, which were widely used for quantifying the absorption energy through entire radiofrequency spectrum, are not appropriate for shallow penetrating MW, and they should be modified when applied to MW frequencies. The new methods developed in our study for determination of MW energy deposition and heating of the skin will be used for establishing adequate dosimetry. The results of the proposed project will be utilized in evaluation of the biophysical mechanisms of the MW interaction with skin structures, and for improving dosimetry in the animal studies of the other projects of the Center.