A Minimally Invasive Microwave Hyperthermic Applicator With an Integrated Temperature Sensor

Abstract

In the field of microwave hyperthermia and thermo-ablation, the use of minimally invasive applicators is recognized as a very promising means for the treatment of small, early stage, cancer lesions because a very thin applicator can be easily introduced inside the body and precisely directed towards a deep seated tumour using the most advanced 3D imaging techniques and surgical stereo-navigation. Minimally invasive applicators have been successfully employed for the treatment of bladder carcinoma and brain tumours but the accurate temperature monitoring of the heated tissue volume still remains an open problem. In this paper we propose a new minimally invasive applicator, integrating a low-cost metallic wired temperature sensor. The miniaturised endocavitary applicator consists of a asymmetric isolated dipole operating at 2.45 GHz. The very slim shape of the applicator allows to easily insert it into the lesion through a soft plastic tube (catheter) while a temperature sensor, properly embedded in the applicator body, measures the tissue temperature at the interface with the catheter surface. An electromagnetic analysis based on the Finite Integration Technique (FIT) and experimental verifications over a tissue sample proved that a coaxial choke, enclosing the temperature sensor wires, allows localize the heating pattern in a restrict volume while drastically reducing measuring artefacts due to the perturbing effects induced by the probe leads.