טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSokolik Dmitry
SubjectPower Absorption in Highly Lossy Biological Tissues:
Electrical Dipole Excitation
DepartmentDepartment of Electrical Engineering
Supervisor Professor Pinchas Einziger


Abstract

The phenomenon of electromagnetic power absorption in biological tissues has recently become of increased scientific and public interest, particularly in the areas of cellular communications and hyperthermia systems. Electromagnetic power absorption in biological tissues is a well-known phenomenon. Its evaluation requires, in general, a solution of the three-dimensional frequency-dependent wave equation in complex configurations, which may necessitate quite massive analytical and numerical efforts. We focus on a simplified dipole source model, which establishes a tight estimate on the optimal (maximal) power absorption in realistic microwave configurations, in particular, cellular communications safety assessment applications. Furthermore, the absorption efficiency as well as the source impedance is obtained via explicit closed-form expressions, leading to an explicit maximal power absorption criterion for highly lossy tissues. The results depend continuously and explicitly on the physical parameters of biological tissues and source location. They are shown to be closely related to electromagnetic Specific Absorption Rate (SAR) estimations in biological tissues. The problem is treated via the extension of a 1-D transmission line model to 3-D cases using the so-called Leontovich surface impedance concept. The extension to the 3-D model is done by incorporating finite-extent sources, i.e. electric or magnetic, vertical or horizontal dipole, exciting a highly-lossy semi-infinite half-space. This modification results in deeper insight and understanding of the crucially important parameters, commonly involved in realistic configurations, namely, bounds and estimates on the power absorption and radiation efficiencies, local and total SAR coupling coefficients, and effective absorption dimensions.