M. J. Piket*, A. Taflove, W. C. Lin, D. S. Katz
EECS Department, McCormick School of Engineering
Northwestern University, Evanston, IL 60208

V. Sathiaseelan
Northwestern Memorial Hospital
Radiation Oncology Center, Rm 44
250 East Superior, Chicago, IL 60611

We have developed a semi-automated method for obtaining patient-specific electromagnetic (EM) hyperthermia models. Using computer vision technology, a patient's computed tomography (CT) scans are analyzed to reconstruct his 3-D tissue geometry. This tissue structure data base is then automatically translated via a software interface to the dielectric media data base of a finite-difference time-domain (FD-TD) numerical EM absorption model, resident on a Cray.

This paper will describe initial results of this procedure. We first provide validation of the FD-TD numerical model for free-space radiated fields from open-ended waveguides and horn antennas (via comparison with the method of moments.) Then, we discuss 2-D and 3-D FD-TD models of EM hyperthermia of a human thigh due to a waveguide applicator, where the thigh data base is derived by analyzing a multiplicity of CT images of a patient.

The 3-D model of the human thigh (using 0.5 cm resolution) is reconstructed from 29 serial CT image slices using the elastic interpolation technique. The boundaries between the fat, muscle, tissue, bone, and bone marrow regions are obtained by thresholding the CT numbers and then applying automatic contour tracing methods. A dielectrically-loaded waveguide (with and without a quarter-wavelength matching layer) is applied to the human thigh data base. The effects of the dielectric loading of the waveguide applicator are shown in plots of the penetrating electric field and specific absorption rate (SAR) for both two and three dimensions, and the two and three dimensional results are compared.