The near-field thermal microwave radiation response of a biological object to the local change of the lateral temperature distribution

Abstract

A layer-by-layer method is theoretically developed for reconstructing the temperature distribution inside a biological object from the measured outgoing thermal microwave radiation energy flux. The measurement is carried out along the plane parallel to the heated object surface in the surface’s near-field area. The equation of the inverse problem is obtained. The equation couples the 2D spatial Fourier-component of Poynting’s outgoing radiation vector with the similar Fourier-component of the lateral temperature distribution along elementary inner layers parallel to the object surface. The obtained equation is solved for the case of a 1D periodic or local depth-uniform lateral temperature distribution inside an object. The effective half-width of the spatial-harmonic spectrum for the outgoing thermal radiation energy flux is shown to be estimated by the double wave number inside the object. At the same time, the spatial half-width of a biological object’s thermal-radiation response to a local change in the lateral temperature distribution is estimated as a half of the wavelength inside the object. This result justifies the antenna size conventionally applied in biomedical research.