Radiofrequency-induced hyperthermia: computer simulation of specific absorption rate distributions using realistic anatomical models

Abstract

A description is given of a computer simulation technique which predicts the specific absorption rate (SAR) distribution within the human body resulting from the application of radiofrequency electromagnetic energy. The method uses an extension to the principle of over-relaxation of electric potentials and the basis of the simulation is a realistic three-dimensional model derived from both dielectric and anatomical data. Two of the principal means of applying radiofrequency hyperthermia, namely the use of capacitive electrodes and inductive coils, have been provided for. The accuracy of the simulation has been favourably tested using an agar split-phantom and an infrared thermograph camera. The simulations can be used to assist the design and clinical use of radiofrequency applicators, and examples are given of the application of both an inductive coil and switched capacitive electrodes to heat the thorax.

Electromagnetic induction tomography

“…Thus, the forward problem is reduced to an electrical network equivalent that is solved accordingly. More details on the impedance method are given in Armitage, Le Veen, and Pethig (1983) and Gandhi, DeFord, and Kanai (1984). Figure 3.12 shows an example of the impedance method applied to a study of head imaging (Dekdouk et al, 2010).…”

Optimal Constrained Field Focusing for Hyperthermia Cancer Therapy: A Feasibility Assessment on Realistic Phantoms

“…The results of the proposed constrained focusing procedure at the two considered frequencies are given in Figures 3(a), (b), where we have reported the SAR distribution resulting from the synthesized field. The SAR has been computed according to the formula [23]:…”

“…Nevertheless, the approach is able to deal with the overall power deposition inasmuch constraints are concerned, and it can be somehow generalized to the case wherein all the three field components have to be maximized by means, for instance, of a multiobjective optimization strategy (see conclusions for more details). Notably, the fact that the approach is able to reach the global optimum under given power deposition constraints allows to state that the achieved Specific Absorption Rate (SAR) [23] distribution can assess the ultimate performances one can achieve (but for the subsequent thermal analysis, which is outside of the scope of the present paper).…”

Spectral analysis of magnetic fields from domestic appliances and corresponding induced current densities in an anatomically based model of the human head

“…For low-frequency dosimetry problems, the impedance method has been found to be highly efficient as a numerical procedure for calculations of internal current densities and induced electric fields [Armitage et al, 1983;Gandhi et al, 1984;DeFord and Gandhi, 1985;Orcutt and Gandhi, 1988;Tofani et al, 19951. In this method, the biological body or the exposed part thereof is represented by a three-dimensional (3-D) network of impedances whose individual values are obtained from the complex conductivities (3 + j o e for the various locations of the body.…”