Fast Optimization of Temperature Focusing in Hyperthermia Treatment of Sub-Superficial Tumors

Microwave hyperthermia aims at selectively heating cancer cells to a supra-physiological temperature. For non-superficial tumors, this can be achieved by means of an antenna array equipped with a proper cooling system (the water bolus) to avoid overheating of the skin. In patient-specific treatment planning, antenna feedings are optimized to maximize the specific absorption rate (SAR) inside the tumor, or to directly maximize the temperature there, involving a higher numerical cost. We present here a method to effect a low-complexity temperature-based planning. It arises from recognizing that SAR and temperature have shifted peaks due to thermal boundary conditions at the water bolus and for physiological effects like air flow in respiratory ducts. In our method, temperature focusing on the tumor is achieved via a SAR-based optimization of the antenna excitations, but optimizing its target to account for the cooling effects. The temperature optimization process is turned into finding a SAR peak position that maximizes the chosen temperature objective function. Application of this method to the 3D head and neck region provides a temperature coverage that is consistently better than that obtained with SAR-optimization alone, also considering uncertainties in thermal parameters. This improvement is obtained by solving the bioheat equation a reduced number of times, avoiding its inclusion in a global optimization process

Vortex Waves and Channel Capacity: Hopes and Reality

International audienceSeveral recent contributions have envisioned the possibility of increasing currently exploitable maximum channel capacity of a free-space link, both at optical and radio frequencies, by using vortex waves, i.e., carrying orbital angular momentum (OAM). Our objective is to disprove these claims by showing that they are in contradiction with very fundamental properties of Maxwellian fields. We demonstrate that the degrees of freedom (DoFs) of the field cannot be increased by the helical phase structure of electromagnetic vortex waves beyond what can be done without invoking this property. We also show that the often-advocated over-quadratic power decay of OAM beams with distance does not play any fundamental role in the determination of the channel DoF

Impact of Different Modeling Approaches in Field Focusing Predictions of Hyperthermia Cancer Therapy

The fundamental aim of an oncological hyperthermia treatment consists in heating the tumour region to a temperature of about 42/43 °C, while keeping the heat in the surrounding healthy tissues in a tolerable range. With the aid of the COMSOL Multiphysics® simulation software and the LiveLink™ for MATLAB® module, we reproduced a typical microwave applicator specifically designed for targeted heating of deep-seated head and neck (H&N) tumours, and we analyze how a SAR-based field optimization on the target volume could be implemented for different models of the neck region