Hyperthermia

Hyperthermia therapy is a kind of cancer treatment to kill or damage cancer cells by elevating the tumor tissues to 40-44°C. Conventionally hyperthermia is an adjunctive therapy used together with radiation or chemotherapy. During hyperthermia treatment, the tumor temperature is increased to a range of 40-44°C for 30-60 min to damage the cancerous cells while leaving the normal tissues undamaged. The applicability of hyperthermia in clinics has been steadily growing because promising results have been achieved. Whole-body, regional, and local hyperthermia treatment thechniques have been a subject of extensive research in past decades.

For hyperthermia treatment device development, electro-thermal simulations on a patient-specific human anatomy model for liver cancer treatment was performed to foresee the selective energy abosorption and heating of tumor and normal tissues based on the difference in dielectric properties and perfunsion. Radiofrequency hyperthermia system with an operating frequency of 13.56 MHz was considered as the heat source. The effect of the different size electrodes and power modulation for selective heating was also determined by predicting avvurate temeprature and thermal dose distribution. Experiments with a tissue-tumor agar phantom were done for validating the simulation findings.

To study the detailed mechanism on hyperthermia therapy and to overcome the limitations with simulation and phantom studies, in-vivo mouse studies are conducted for squamous cell carcinoma of the lung. This study determined the effect of tumor properties on energy absorption, temeprature mapping, and thermal dose distribution in mild radiofrequency hyperthermia using a mouse xenograft model. Simulations were performed on a computed tomography mouse model. Dielectric properties of tumors were measured, and temeprature dependence were considered for thermal properties, metabolic heat generation, and perfusion. Our results showed that dielectric property variations were ore dominant than thermal properties and other parameters, and the measured dielectirc properties provided relatively more improved temeprature-mapping than the property values taken from previous study. Furthermore, consideration of temperature dependent thermal properties allowed elucidation of accurate temperature mapping to enable precise thermal-dose calculations.

The therapeutic outcomes of combined hyperthermia and radiation therapy can be calculated based on equivalent radiation dose. Thermal enhancement of radiosensitization depends on the targeted temeprature and type of cell line, and the effects in different cell lines are unknown. The combined therapeutic effects are calcultaed numerically as the equivalent radiation dose for lung cancer cell line A549. We found that the radiation dose increased when hyperthermia was applied. Overall, our study would contribute to effective thermoradiotherapy planning in clinics.

Biomedical Device Laboratory

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Research