A study on the variation of dielectric properties of grey matter with temperature

Microwave hyperthermia is used in conjunction with radiotherapy and chemotherapy to provide a more effective way of treating cancer in the brain. The dielectric properties of brain tissue are important in predicting specific absorption rate (SAR) patterns in the brain. This study investigates the variation of brain dielectric properties as a function of frequency and temperature as these are crucial for SAR calculations, and hence treatment planning. We measured dielectric properties of freshly excised porcine brain tissues over the frequency range 0.4 to 20 GHz from room temperature to 60 °C. The results show that the permittivity decreases with temperature at all frequencies while the conductivity does not vary significantly below 1 GHz and decreases above this frequency.