Droop: a rapidly computable descriptor of local minimum tissue temperature during conductive interstitial hyperthermia.
Although the goal of local hyperthermia therapy for cancer is to elevate the temperature of a tumour to cytotoxic levels, without the presence of 'cold spots', varying blood flow has made the achievement of consistent, therapeutic temperature distributions extraordinarily difficult. The paper presents a novel approach to estimating local minimum tumour temperatures during conductive interstitial hyperthermia which facilitates identification and elimination of cold spots. Conductive interstitial hyperthermia is modelled mathematically for a parallel array of implanted, electrically heated catheters which warms the treated tissue by thermal conduction and blood perfusion. Computer simulations employing the bioheat transfer equation reveal a predictive relationship between implanted catheter temperature, catheter power, implantation geometry and local minimum tumour temperature. Formulation of this relationship in terms of a parameter named 'droop' allows estimation of local minimum intratumoural temperatures from individual catheter temperature and power. Computer simulations are also performed to determine the sensitivity of the droop-based estimator to variations in properties of the tissue and catheters. Generally, variations in geometry or thermal properties of about 10 per cent cause estimation errors of less than 1 degree C in magnitude. These results suggest that online estimates of thermal 'droop' may provide a practical route to more consistent control of intratumoural minimum temperature during conductive interstitial heat therapy.
DeFord
J A
JA
W.A. Hillenbrand Biomedical Engineering Center, Purdue University, West Lafayette, IN 47907.
Babbs
C F
CF
Patel
U H
UH
D000465:Algorithms; D001831:Body Temperature / Q000502:physiology*; D006801:Humans; D006979:Hyperthermia, Induced; D008954:Models, Biological; D009369:Neoplasms / Q000503:physiopathology