How to apply a discrete vessel model in thermal simulationswhen only incomplete vessel data are available

Abstract

For accurate predictions of the temperature distribution during hyperthermiatreatment a thermal model should incorporate the individual impact of discretevessels. In clinical practice not all vessels can be reconstructedindividually. This paper investigates five possible strategies to model thethermal impact of these missing vessels.A tissue volume with a detailed, realistic, counter-current discretevasculature is heated and the steady-state temperature distribution iscalculated using our DIscrete VAsculature (DIVA) thermal model. To mimicincomplete discrete vasculatures the full tree is gradually stripped, that is,the number of discretely described vessels is reduced in four steps until nodiscrete vessels are left.At each strip level the steady state temperature distribution is calculatedfor five different strategies to model the missing vessels. The strategies alluse a local or global heat sink model in addition to the discrete vasculature.The resulting temperature distributions are compared with the full treesimulation.With increasing strip level the correspondence with the full tree simulationdeteriorated for all strategies. An optimal strategy was found to model themissing vessels depending on the available angiographic data. It was alsofound that simulations with a decreased number of discrete vessels, or novessels at all, yield temperatures which are too high. Theoretically this can becompensated by increasing the thermal conductivity; finding the optimal valueis done empirically.