Power density and temperature distributions produced by interstitial arrays of sleeved-slot antennas for hyperthermic cancer therapy

A graded-mesh finite-difference time-domain (FDTD) code, together with an alternate-direction-implicit finitedifference (ADI-FD) solution of the bioheat equation, are used for studying arrays of sleeved-slot antennas imbedded in a brain-equivalent phantom. The FDTD code allows efficient and accurate modeling of the fine structure of each antenna and of a sufficiently wide surrounding region. The ADI-FD solution of the bioheat equation allows evaluation of transient and steady-state temperature distributions in the brain-equivalent phantom with acceptable computational costs. The solution of the dosimetric-thermal problem in the volume irradiated by the antenna array permits the assessment of dimensions of the region where the temperature increase is above 43(degree)C (the threshold for an effective hyperthermia treatment) as a function of the array input power. Arrays made of three identical antennas placed at the vertices of equilateral triangles of 10-, 15-, and 20-mm sides have been studied. The temperature of 43(degree)C is reached in approximately 3 min in a deep-seated tumor region, from 10 to 40 mm in diameter, by applying input power levels between 2-32 W.