Paolo Togni

Clinical integration of software tool VEDO for adaptive and quantitative application of phased array hyperthermia in the head and neck.

Abstract Background and purpose: In Rotterdam, patient-specific hyperthermia (HT) treatment planning (HTP) is applied for all deep head and neck (H&N) HT treatments. In this paper we introduce VEDO (the Visualisation Tool for Electromagnetic Dosimetry and Optimisation), the software tool required, and demonstrate its value for HTP-guided online complaint-adaptive (CA) steering based on specific absorption rate (SAR) optimisation during a H&N HT treatment. Materials and methods: VEDO integrates CA steering, visualisation of the SAR patterns and mean tumour SAR (SARtarget) optimisation in a single screen. The pre-calculated electromagnetic fields are loaded into VEDO. During treatment, VEDO shows the SAR pattern, overlaid on the patients’ CT-scan, corresponding to the actually applied power settings and it can (re-)optimise the SAR pattern to minimise SAR at regions where the patient senses discomfort while maintaining a high SARtarget. Results: The potential of the quantitative SAR steering approach using VEDO is demonstrated by analysis of the first treatment in which VEDO was used for two patients using the HYPERcollar. These cases show that VEDO allows response to power-related complaints of the patient and to quantify the change in absolute SAR: increasing either SARtarget from 96 to 178 W/kg (case 1); or show that the first SAR distribution was already optimum (case 2). Conclusion: This analysis shows that VEDO facilitates a quantitative treatment strategy allowing standardised application of HT by technicians of different HT centres, which will potentially lead to improved treatment quality and the possibility of tracking the effectiveness of different treatment strategies.

Design of a wideband multi-channel system for time reversal hyperthermia.

Purpose: To design and test a wideband multi-channel amplifier system for time reversal (TR) microwave hyperthermia, operating in the frequency range 300 MHz–1 GHz, enabling operation in both pulsed and continuous wave regimes. This is to experimentally verify that adaptation of the heating pattern with respect to tumour size can be realised by varying the operating frequency of the antennas and potentially by using Ultra-wideband (UWB) pulse sequences instead of pure harmonic signals. Materials and methods: The proposed system consists of 12 identical channels driven by a common reference signal. The power and phase settings are applied with resolutions of 0.1 W and 0.1°, respectively. Using a calibration procedure, the measured output characteristics of each channel are interpolated using polynomial functions, which are then implemented into a system software algorithm driving the system feedback loop. Results: The maximum output power capability of the system varies with frequency, between 90 and 135 W with a relative power error of ±6%. A phase error in the order of ±4° has been achieved within the entire frequency band. Conclusions: The developed amplifier system prototype is capable of accurate power and phase delivery, over the entire frequency band of the system. The output power of the present system allows for an experimental verification of a recently developed TR-method on phantoms or animals. The system is suitable for further development for head and neck tumours, breast or extremity applications.

Microwave applicator for hyperthermia treatment on in vivo melanoma model

In this article, we evaluated a planar microwave applicator for in vivo superficial hyperthermia treatments on small tumors in the mouse mimicking treatments for human neoplasms. The design of the applicator, was challenged by the small dimensions of the tumors and unwanted diffusion of heating in the tumor-bearing animals. The required solution was to limit the penetration of microwaves in the depth of the tissue maintaining the full efficacy of hyperthermia. The study was firstly performed by computer simulations of SAR distribution inside a flat homogeneous phantom, considering various thicknesses of the integrated water bolus. Simulations, validated by the measurements, were also used to evaluate the impedance matching. Further tests were performed on homogeneous agar phantom to simulate the temperature distribution in the biological tissue and to preliminary assess the possible modality and schedule of microwave hyperthermia delivery. The in vivo experiments showed the evidence of direct microwave-induced heating and damage of the melanoma tissue in a range of penetration coherent both with computer simulations and phantom studies. The described approach appears perspective for designing limited-microwave-delivery applicators tailored for treatments of human superficial tumors and pre-tumoral lesions.

Feasibility Study of Superficial Hyperthermia Treatment Planning Using COMSOL Multiphysics

Microwave hyperthermia is a promising method of cancer treatment used to increase the temperature within the interval of 40 - 44degC. The goal of this paper is to introduce the possibility of treatment planning for superficial hyperthermia using COMSOL Multiphysics. The real model of the patient with recurrent breast cancer was developed. The waveguide horn applicator with aperture of 10 x 10 cm was used for the planning. Results of impedance matching and 3D SAR distribution are presented.

System to Study the Effects of Microwave Hyperthermia on In-vivo Melanoma Model

The use of hyperthermia as anti-cancer treatment in combination with other therapies assumes every day a growing interest. In this paper the main characteristics of a microwave system and an applicator for hyperthermia treatment of small in-vivo melanoma tumours are described. The results of temperature measurements on mice, show the possibility to design a protocol for hyperthermia treatment of small animal with superficial tumours for the evaluation of hyperthermia effects.

Slot-line applicator for microwave hyperthermia.

Electromagnetic field interaction with biological tissues and their applications in cancer treatment research has become of growing interest. This paper describes the possibility of using a slot-line type applicator for microwave hyperthermia treatment in oncology. What we aim to show in this paper is that this type of applicator is particularly suitable for the treatment of superficial cancers with depths 2–3 cm below the body surface. To support this thesis, a 3D electromagnetic field simulator has been used to predict the specific absorbed ratio (SAR), and the consequent temperature distribution in the area under treatment. The results of the simulations are supported by experimental temperature measurements made with the help of an infrared thermo-camera on a homogeneous agar phantom. The possibility to use an array configuration of this applicator in order to treat bigger areas is also analyzed using computer simulation of SAR distribution.

COMSOL Multiphysics in Undergraduate Education of Electromagnetic Field Biological Interactions

In this paper we present a basic model created in COMSOL Multiphysics for undergraduate education purposes in courses dealing with biological effects of electromagnetic fields, electromagnetic fields in biological systems. COMSOL Multiphysics provides possibility to combine various physical processes described by differential equations to one simulation. Easy-to-do and attractive graphical post-processing of the calculated results in COMSOL Multiphysics are very useful for presentation in classroom and lecture what increases students’ interest in the subject as well as their attention.

Modified Microstrip Ring Applicator for Superficial Hyperthermia

Nowadays hyperthermia is one of the possible cancer treatment method used in combination with classical therapies in several countries in the world. In this article we described the designed and optimization of a microstrip type applicator for the treatment of superficial diseases. The optimization was made in order to obtain a more uniform SAR distribution, which is one of the requirements to achieve a good thermotherapy treatment.

Design and Comparison of Exposure Chambers for Verification of Microwave Influence on Biological Systems

The main aim of our work is to design and simulate an exposure chamber in order to analyze the influence of electromagnetic field on mice which can simulate mobile phone emission patterns. We use two types of structures and compare their properties to find the best design for our future work.

Applicator for In-vivo Experiments on Mice with Melanoma Tumour

The use of electromagnetic fields in biomedicine for cancer treatment and diagnostics, nowadays begin to be quite widespread. This paper describes the design and the evaluation of a microwave applicator for treatment of small subcutaneous tumours implanted on animal model. The support of computer simulations was used to evaluate and optimise the fundamental parameters of the applicator and the SAR distribution in the biological tissue. The Results give the prospective to use this applicator for the study of the effects of hyperthermia treatment in relation with the characteristics of the treated tumour.