Numerical Model for Magnetic Fluid Hyperthermia in a Realistic Breast Phantom: Calorimetric Calibration and Treatment Planning.

Arkadiusz Miaskowski,Mahendran Subramanian

doi:10.3390/ijms20184644

Abstract

This paper aims to apply a proposed, based on calorimetric measurements, a reliable numerical model for magnetic fluid hyperthermia (MFH) treatment planning of breast cancer. Furthermore, we perform a comparative analysis of magnetic nanoparticles (MNPs) and tumour tissue interactions by means of the magnetic-field-dependent Néel and Brownian relaxation times. The analysis was based on an anatomically correct breast model (developed in-house) and a modified linear response theory, which was applied to investigate the heat dissipation from the magnetic nanoparticles dispersed in the breast tumour. The calculations of the single-domain magnetic power losses were conducted for a case where the magnetic field value and the applied frequency were known, but also for the different concentrations of the MNPs in the tumour. Two scenarios were considered: The MNPs mobilised and immobilised in the tumour. In parallel, the eddy currents effect, together with the related temperature distributions, were considered in order to analyse safety issues. By changing the MNP concentration in the tumour, the corresponding temperature distributions were calculated. The eddy current effect, together with the related temperature distribution, were considered in order to analyse safety issues. Varying the MNP concentration in the tumour, the corresponding temperature distribution was calculated. Moreover, the cumulative equivalent minutes at were analysed. In the anatomically correct breast phantoms, the tissue location can lead to “hot spots” due to the eddy current effect and subsequently to the high gradients of the temperature. That is why the analysis of safety issues related to the overheating side effect should be taken into consideration during the treatment planning of magnetic fluid hyperthermia. The phenomenon of heat dissipation from MNPs is very sophisticated and depends on their concentration, the distribution and the relaxation mechanism in the tumour, together with magnetic field strength and frequency. Furthermore, we inferred that the phenomenon of heat dissipation from MNPs equally depends on MNP-tissue interactions, and it can lead to 30% differences in the power assessment. Nevertheless, the aforementioned factors should be considered in parallel using anatomical, volume-dependent models to enhance the efficiency of in vivo treatment.

Highlights

Novel therapy methods without negative impacts are needed to reduce mortality rates in patients with breast cancer
In addition to the power losses due to the eddy current effect, a power dissipation from magnetic nanoparticles should be considered in parallel when dealing with magnetic fluid hyperthermia (MFH) treatment planning
Particular interest was paid to the comparative analysis of magnetic nanoparticles (MNPs)–tissue interactions, as in MFH, and the heating rates of MNPs which were determined using Néel and Brownian losses, which can be inappropriate for MFH treatment

Summary

Introduction

Novel therapy methods without negative impacts are needed to reduce mortality rates in patients with breast cancer. Ethical factors, cost-effective clinical trials and infrastructure requirements restrict the number of teams performing in vivo studies, hampering significant progress in understanding MFH for the therapy of breast cancer. Constraints such as those for the pain threshold of 4.85 × 108 A/m/s for induced eddy currents in patients during MFH treatment [9] and the field limit being sufficient to saturate all the particles within the distribution at a particular frequency, limit MFH treatment. It is possible to use virtual breast phantom models to evaluate the efficacy of MFH and the risk assessment of the radiofrequency

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Conclusion