Jeantide Said Camilleri

Electromagnetic thermal therapies for cancer treatment, such as microwave hyperthermia, aim to heat up a targeted tumour site to temperatures within 40 and 44 °C. Computational simulations used to investigate such heating systems employ the Pennes’ bioheat equation to model the heat exchange within the tissue, which accounts for several tissue properties: density, specific heat capacity, thermal conductivity, metabolic heat generation rate, and blood perfusion rate. We present a review of these thermal and physiological properties relevant for hyperthermia treatments of breast including fibroglandular breast, fatty breast, and breast tumours. The data included in this review were obtained from both experimental measurement studies and estimated properties of human breast tissues. The latter were used in computational studies of breast thermal treatments. The measurement methods, where available, are discussed together with the estimations and approximations considered for values where measurements were unavailable. The review concludes that measurement data for the thermal and physiological properties of breast and tumour tissue are limited. Fibroglandular and fatty breast tissue properties are often approximated from those of generic muscle or fat tissue. Tumour tissue properties are mostly obtained from approximating equations or assumed to be the same as those of glandular tissue. We also present a set of reliable data, which can be used for more accurate modelling and simulation studies to better treat breast cancer using thermal therapies.

This paper presents an investigation of two dipole antennas working at 434 MHz and 2.45 GHz as a tool to understand the mechanisms to optimise microwave hyperthermia (MWH) for breast cancer. The investigations were performed on a numerical breast phantom with a water bolus kept at 25 °C developed in CST Studio Suite. The bolus thickness and dipole placements with respect to the breast were varied and an optimal scenario was selected. A layer of fat was then added to these models where the effect of fat on the temperature distribution was investigated. The results show that the 434 MHz dipole requires further improvements, but a hotspot located well below the surface of the breast suggests its usefulness for deep-seated tumours. In contrast, the 2.45 GHz dipole is a good candidate for superficial MWH where the matching, power required and hotspot focusing were superior.