Articles techniques et présentations

Microwave hyperthermia (HT) offers a promising approach to cancer treatment by selectively heating tumors to temperatures between 42-44°C, enhancing the efficacy of radiotherapy and chemotherapy [1]. To effectively treat deep-seated and sub-superficial tumors, state-of-the-art clinical HT involves phased-array antenna applicators and patient-specific numerical simulations for Hyperthermia Treatment Planning (HTP) [2]. This work explores the development of an experimental mock-up reproducing a hyperthermia treatment in the head and neck (H&N) region and its in-silico counterpart simulated in COMSOL Multiphysics®. The prototype consists of a Poly(methyl methacrylate) (PMMA) container (circumradius 20 cm, height 12 cm) hosting a circular array of eight patch antennas with water substrate [3]. A central PMMA cylinder, filled with a phantom mimicking the dielectric properties of the human muscle [4], represents the patient's neck tissue, while one solid and one hollow cylinder simulate the spine and trachea, respectively. The water between the neck and the array forms the so-called waterbolus, used in clinical practice to prevent skin overheating and enhance energy coupling. A digital twin of the prototype was developed in COMSOL Multiphysics® by integrating the experimentally measured dielectric and thermal properties of the fabricated phantom [5] into the simulation domain. Later, LiveLink for MATLAB was used to find the optimal antenna array coefficients that focus the power deposition (specific absorption rate, SAR) on a target sphere representing the tumor, minimizing the risk of hotspots in the surrounding healthy tissue. The BioHeat Transfer (BT) Module was then used to generate the temperature distribution. The optimized array’s feeding coefficients from COMSOL were experimentally assigned to the antennas using a properly developed electronic setup. To experimentally verify the localized heating of the tumor target region, temperature measurements in different locations and in real-time were performed in the prototype using a system of Fiber Optic Sensors (FOS), which consisted of arrays of Fiber Bragg Gratings (FBGs). The temperature measurements were compared to the values obtained in the COMSOL model, where the transient bioheat equation was solved after assigning the initial and boundary conditions that best reproduce the characteristics of the prototype and the surrounding environment during the heating session. The results demonstrated that the applicator effectively focuses the microwave energy on the tumor target, and a very good agreement between experimental and simulated temperatures was observed during the entire heating session, proving the ability of COMSOL Multiphysics® to create a reliable digital twin of a H&N microwave hyperthermia applicator.