Use of vascular and non-vascular models for the assessment of temperature distribution during induced hyperthermia

Abstract

We developed a three-dimensional thermal model in which convective heat transfer in a human extremity is explicitly quantified by taking into account the physical details of the vascular system. The spatial pattern in the arterial, venous and tissue temperature is computed during hyperthermia treatment. As such a complex vascular model is not generally applicable, a comparative study of the results of simpler, substitutional, non-vascular concepts applied to hyperthermia was carried out. It turned out that classical bioheat approaches may lead to wrong conclusions. Satisfactory results are to be expected from an approach suggested by Wissler/Baish and Charny/Levin, and by a far simpler efficiency function (EF) concept, developed by us, that can be used as easily as the simple classical Pennes approach while avoiding its deficiencies. The EF model is used to predict whether the temperature of the entire volume of vascularized muscle tissue will be raised to a therapeutic level. With the help of the vascular model, local thermal non-uniformities near individual blood vessels are analysed. Underheating in small volumes of tissue near the vessel walls is detected. This might explain tumour regrowth following local hyperthermia treatment in the tissue adjacent to blood vessels.

Radiofrequency Heating Models and Measurements

“…Statistically, significant errors may result in predicting tissue temperatures. 32,43, 44 Nevertheless, in applications where blood temperature does not vary significantly along the blood flow direction, Pennes' BHTE predicts accurate volume-averaged tissue temperature distributions. In applications where blood temperature varies appreciably along the blood flow direction, use of an "average" blood temperature may provide useful indications about the general nature of volume-averaged tissue temperature distributions.…”

Thermal responses for men with different fat compositions during immersion in cold water at two depths: prediction versus observation

“…Although thermal responses to cold have been well studied, there is limited quantitative information and knowledge about how cold impacts regional blood Xows. Modeling techniques have been long used to investigate the eVects of blood Xow on local tissue temperature distribution during induced regional hyperthermia therapies (Brinck and Werner 1995;Kolios et al 1998;Alekssev et al 2005). CTM simulation demonstrated the potential contribution of muscle blood Xow to T c cooling by means of a whole body thermoregulatory model.…”

Planning, optimisation and evaluation of hyperthermia treatments

“…There has been significant progress in thermal modelling with discrete vasculature and several models exist that account for straight or semi-curved vessels [74][75][76][77], but the possibility to include 3D discrete vasculature networks is a unique feature of the Plan2Heat software package. First steps towards the use of advanced discrete vessel models are taken by companies distributing commercial software, but currently boundary conditions are applied to account for the effect of large blood vessels rather than modelling real 3D curved vasculature.…”