Measurement of specific loss power (SLP) of magnetic nanoparticles is crucial to assert the heating potential in magnetic hyperthermia. There has been a significant improvement in characterizing magnetic nanoparticles’ heat-triggered functions by many research groups. However, optimal experimental conditions along with notable determination methods of the SLP in magnetic hyperthermia have not been widely proposed until now. Despite the remarkable progress in this field, the evaluation process of SLP suffers from uncertainties and errors imposed not only by experimental parameters (depending on the particles, the conditions and the measurement) but by the estimation methodology, as well. In this work, we propose a step by step standardization protocol, starting from definition and recording of potential uncertainty and error sources, present during a typical magnetic hyperthermia experimental protocol. The error of each specific parameter is estimated and translated to ultimate heating efficiency evaluation. According to our analysis, magnetic hyperthermia experiment and its corresponding estimation, under non-adiabatic conditions, may lead to a propagated uncertainty up to 14% on the SLP value. Meanwhile, different heating evaluation methods were assessed under a wide range of experimental conditions, with the ‘modified law of cooling’ proving to be the most accurate one—limiting the SLP uncertainty to values under 5%—compared to the ‘initial slope’ and ‘Box–Lucas’ methods, which show a remarkable uncertainty of over 15%. All parameters involved in the heating efficiency evaluation and their associated uncertainties analysis presented in this work, are included in a standardisation protocol, a handy guideline for determining accurate, reliable and reproducible SLP values, thus adequately evaluating its impact in potential bioapplications.

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Single- and dual-antenna arrays systems operating at 2.45 GHz yield larger ablation zone due to greater power deposition in proximity to the antenna, as well as greater role of thermal conduction.

Clinical outcome of hyperthermia depends on the achieved target temperature, therefore target conformal heating is essential. Currently, invasive temperature probe measurements are the gold standard for temperature monitoring, however, they only provide limited sparse data. In contrast, magnetic resonance thermometry (MRT) provides unique capabilities to non-invasively measure the 3D-temperature. This study investigates MRT accuracy for MR-hyperthermia hybrid systems located at five European institutions while heating a centric or eccentric target in anthropomorphic phantoms with pelvic and spine structures. Scatter plots, root mean square error (RMSE) and Bland–Altman analysis were used to quantify accuracy of MRT compared to high resistance thermistor probe measurements. For all institutions, a linear relation between MRT and thermistor probes measurements was found with R2 (mean ± standard deviation) of 0.97 ± 0.03 and 0.97 ± 0.02, respectively for centric and eccentric heating targets. The RMSE was found to be 0.52 ± 0.31 °C and 0.30 ± 0.20 °C, respectively. The Bland-Altman evaluation showed a mean difference of 0.46 ± 0.20 °C and 0.13 ± 0.08 °C, respectively. This first multi-institutional evaluation of MR-hyperthermia hybrid systems indicates comparable device performance and good agreement between MRT and thermistor probes measurements. This forms the basis to standardize treatments in multi-institution studies of MR-guided hyperthermia and to elucidate thermal dose-effect relations.

Microwave ablation (MWA) is a minimally invasive thermal therapy modality increasingly employed for the treatment of tumors and benign disease. For successful treatment, complete thermal coverage of the tumor and margin of surrounding healthy tissue must be achieved. Currently available interstitial antennas for MWA have cylindrically symmetric radiation patterns. Thus, when treating targets in proximity to critical structures, caution must be taken to prevent unintended thermal damage. A novel coaxial antenna design for MWA with an asymmetrical cylindrical heating pattern is presented in this paper. This radiation pattern is achieved by employing a hemicylindrical reflector positioned at a critical distance from a conventional coaxial monopole antenna. Finite-element method simulations were employed to optimize the geometric dimensions of the antenna with the objective of minimizing the antenna reflection coefficient at the 2.45-GHz operating frequency, and maximizing volume of the ablation zone. Prototype antennas were fabricated and experimentally evaluated. Simulations indicated an optimal S11 of -32 dB at 2.45 GHz in close agreement with experimental measurements of -29 dB. Ex vivo experiments were performed to validate simulations and observe effects to the antennas' heating pattern with the varying input power and geometry of the reflector. Ablation zones up to 20 mm radially were observed in the forward direction, with minimal heating (less than 4 mm) behind the reflector.