Effect of the Water Bolus and Tissue Thickness Over the Heat Distribution Generated by a RF Applicator Used as an Auxiliar to Treat Bone Tumors

It is estimated that 3610 new cases of bone cancer would be diagnosed by 2021. Oncological hyperthermia is a procedure used to elevate the temperatures in the tumors around 40°C-45°C for times between 60 min.-90min. One of the disadvantages of external applicators to treat bone tumors is the risk of overheat skin and superficial tissues, without reach the bone tissue. To evaluate this problem, it was proposed a modeling based on the finite element method, of a hyperthermia treatment for tumors at the muscle-bone interface. A previously designed rectangular waveguide that works at 250 MHz was proposed for this study. The effect, over the temperature distribution, of water bolus thicknesses and temperature, as well as treatment times and input powers were analyzed. The maximum reached temperature and the Standing Wave Ratio (SWR) at different penetration depths, by considering skin, fat, muscle, and bone, were obtained. A maximum temperature of 44.63°C was obtained at a depth of 32.35 mm, for a 5 mm water bolus when 100 W were applied for 90 minutes. This penetration deep and the reached temperature could be adequate to use this applicator in the treatment of tumors in the muscle-bone interface.