Comparative study of heat transfer and thermal damage assessment models for hyperthermia treatment.

Appropriate heating of the tumor can ablate tumor cells with minimal damage to healthy tissue and low side effects to the patient. Therefore, it is important to estimate power dissipation requirement and predict thermal damage in tumor before hyperthermia treatment. This work applied a mathematical model on heat transfer in two-layered spherical tissue to predict the temperature profile within hyperthermia domain. The present bioheat transfer problem was analyzed based on the Pennes equation, the thermal wave and dual-phase lag modes in order to explore the effect of analysis mode on the power dissipation requirement. The Arrenius equation, the modified thermal damage model with regeneration term, and the equivalent thermal dose equation were used to evaluate the thermal damage and discuss their effects on thermal damage prediction. The computation results show that the model of bioheat transfer and the non-Fourier effect significantly affects the power dissipation requirement. The damage parameter value predicted by the modified thermal damage model with regeneration term seems to have a limit value of Ω = 1. The results imply that the regeneration of biological tissue can prevent the tissue from thermal damage, the equivalent thermal dose equation is more related to heating time, and the Arrenius equation is more related to heating temperature.

Scintigraphic assessment of salivary function after intensity-modulated radiotherapy for head and neck cancer: correlations with parotid dose and quality of life.

OBJECTIVE: We investigated salivary function using quantitative scintigraphy and sought to identify functional correlations between parotid dose and quality of life (QoL) for head and neck cancer (HNC) patients receiving intensity-modulated radiotherapy (IMRT). MATERIALS AND METHODS: Between August, 2007 and June, 2008, 31 patients treated IMRT for HNC were enrolled in this prospective study. Salivary excretion function (SEF) was previously measured by salivary scintigraphy at annual intervals for 2 years after IMRT. A dose-volume histogram of each parotid gland was calculated, and the normal tissue complication probability (NTCP) was used to determine the tolerance dose. QoL was longitudinally assessed by the EORTC QLQ-C30 and H&N35 questionnaires prior to RT, and at one, three, 12 and 24 months after RT. RESULTS: A significant correlation was found between the reduction of SEF and the mean parotid dose measured at 1 year (correlation coefficient, R(2)=0.651) and 2 years (R(2)=0.310) after IMRT (p<0.001). The TD(50) of the parotid gland at 1 year after IMRT is 43.6 Gy, comparable to results from western countries. We further found that contralateral parotid and submandibular gland function preservation was correlated with reduced sticky saliva and a better QoL compared to the functional preservation of both parotid glands, as determined by the EORTC QLQ-H&N35 questionnaire. CONCLUSION: A significant correlation was found between the reduction of SEF and the mean parotid dose. Preservation of contralateral parotid and submandibular gland function predicts a better QoL compared to preservation of the function of both parotid glands.