TEMPERATURE-DEPENDENT VERSUS CONSTANT-RATE BLOOD PERFUSION MODELING IN FERROMAGNETIC THERMOSEED HYPERTHERMIA - RESULTS WITH A MODEL OF THE HUMAN PROSTATE

Finite-element solutions to the Pennes bioheat equation are obtained w ith a model of a tumour-containing, human prostate and surrounding nor mal tissues. Simulations of ferromagnetic hyperthermia treatments are conducted on the tissue model in which the prostate is implanted with an irregularly spaced array of thermoseeds. Several combinations of th ermoseed temperatures with different Curie points are investigated. No n-uniform, constant-rate blood perfusion models are studied and compar ed with temperature-dependent descriptions of blood perfusion. Blood p erfusions in the temperature-dependent models initially increase with tissue temperature and then decrease at higher temperatures. Simulatio ns with temperature-dependent versus constant-rate blood perfusion mod els reveal significant differences in temperature distributions in and surrounding the tumour-containing prostate. Results from the simulati ons include differences (between temperature-dependent and constant-ra te models) in (1) the percentage of normal tissue volume and tumour vo lume at temperatures > 42-degrees-C, and (2) temperature descriptors i n the tumour (subscript t) and normal (subscript n) tissues including T(max,t), T(min,t) and T(max,n). Isotherms and grey-scale contours in the tumour and surrounding normal tissues are presented for four simul ations that model a combination of high-temperature thermoseeds. Sever al simulations show that T(min,t) is between 1.7 and 2.6-degrees-C hig her and T(max,n) is between 2.1 and 3.3-degrees-C higher with a temper ature-dependent versus a comparable constant-rate blood perfusion mode l. The same simulations reveal that the percentages of tumour volume a t temperatures > 42-degrees-C are between 0 and 68% higher with the te mperature-dependent versus the constant-rate perfusion model over all seed combinations studied. In summary, a numerical method is presented which makes it possible to investigate temperature-dependent, continu ous functions of blood perfusion in simulations of hyperthermia treatm ents. Simulations with this numerical method reveal that the use of co nstant-rate instead of temperature-dependent blood perfusion models ca n be a conservative approach in treatment planning of ferromagnetic hy perthermia.