Numerical Model Study of In Vivo Magnetic Nanoparticle Tumor Heating

Sol-gel dip-coated TiO2 nanofilms reduce heat production in titanium alloy implants produced by microwave diathermy

Objective: To verify that the TiO₂ nanofilm dip-coated by sol-gel can reduce titanium alloy implants (TAI)'s heat production after microwave diathermy (MD).Methods: The effect of 40 W and 60 W MD on the titanium alloy substrate coated with TiO₂ nanofilm (Experimental Group) and the titanium alloy substrate without film (Control Group) were analyzed in vitro and in vivo. Changes in the skeletal muscle around the implant were evaluated in ex vivo by histology.Results: After 20 min of MD, in vitro the temperature rise of the titanium substrate was less in the Experimental Group than in the Control Group (40 W: 1.4 °C vs. 2.6 °C, p < .01, 60 W: 2.5 °C vs. 3.7 °C, p < .01) and in vivo, the temperature rise of the muscle tissue adjacent to TAI was lower in the Experimental Group than in the Control Group (40 W: 3.29 °C vs. 4.8 °C, p < .01, 60 W: 4.16 °C vs. 6.52 °C, p < .01). Skeletal muscle thermal injury can be found in the Control Group but not in the Experimental Group.Conclusion: Sol-gel dip-coated TiO₂ nanofilm can reduce the heat production of TAIs under single 40～60 W and continuous 40 W MD and protect the muscle tissue adjacent to the implants against thermal injury caused by irradiation.

Biological thermometer based on the temperature sensitivity of magnetic nanoparticle paraSHIFT

In the paper, the temperature dependence of magnetic nanoparticle (MNP) paramagnetic chemical shift (paraSHIFT) was studied by magnetic resonance (MR) spectroscopy. Based on it, iron oxide MNPs are considered as MR shifting probes for determining the temperature in liquids. With the increase in measurement temperature of the MNP reagent with MNPs, the decrease of MNP magnetization would make the peak of spectroscopy shift to the higher chemical shift area. The peak shift is related to the magnetic susceptibility of MNPs, which can be determined by MR frequency as a function of temperature and particle size. Experiments on temperature-dependent chemical shifts are performed for MNP samples with different core sizes and the estimated temperature accuracy can achieve 0.1 K. Combined with the contrast effect of magnetic nanoparticles in magnetic resonance imaging at 3 T, this technology can realize temperature imaging.

A Computational Study on Magnetic Nanoparticles Hyperthermia of Ellipsoidal Tumors

The modelling of magnetic hyperthermia using nanoparticles of ellipsoid tumor shapes has not been studied adequately. To fill this gap, a computational study has been carried out to determine two key treatment parameters: the therapeutic temperature distribution and the extent of thermal damage. Prolate and oblate spheroidal tumors, of various aspect ratios, surrounded by a large healthy tissue region are assumed. Tissue temperatures are determined from the solution of Pennes’ bio-heat transfer equation. The mortality of the tissues is determined by the Arrhenius kinetic model. The computational model is successfully verified against a closed-form solution for a perfectly spherical tumor. The therapeutic temperature and the thermal damage in the tumor center decrease as the aspect ratio increases and it is insensitive to whether tumors of the same aspect ratio are oblate or prolate spheroids. The necrotic tumor area is affected by the tumor prolateness and oblateness. Good comparison is obtained of the present model with three sets of experimental measurements taken from the literature, for animal tumors exhibiting ellipsoid-like geometry. The computational model enables the determination of the therapeutic temperature and tissue thermal damage for magnetic hyperthermia of ellipsoidal tumors. It can be easily reproduced for various treatment scenarios and may be useful for an effective treatment planning of ellipsoidal tumor geometries.

Improving magnetic nanothermometry accuracy through mixing-frequency excitation

This study proposes a temperature model for the relaxation of magnetic nanoparticles and a phase measurement method under a mixing-frequency excitation field, which can improve the accuracy of temperature measurements in magnetic nanothermometry. According to the Debye-based magnetization model for magnetic nanoparticles, phases at mixing frequencies are used to solve the problem of a delay in the relaxation phase of the magnetic field at a high frequency. This method can improve the signal-to-noise ratio of the response of the magnetic nanoparticles and weaken the phase shift of the detection coils caused by the changes in temperature. The results of experiments show that the proposed method can achieve static temperature measurement error less than 0.1 K and dynamic temperature measurement error less than 0.2 K.

In vivo magnetic nanoparticle hyperthermia: a review on preclinical studies, low-field nano-heaters, noninvasive thermometry and computer simulations for treatment planning

Magnetic nanoparticle hyperthermia (MNH) is a promising nanotechnology-based cancer thermal therapy that has been approved for clinical use, together with radiation therapy, for treating brain tumors. Almost ten years after approval, few new clinical applications had appeared, perhaps because it cannot benefit from the gold standard noninvasive MRI thermometry technique, since static magnetic fields inhibit heat generation. This might limit its clinical use, in particular as a single therapeutic modality. In this article, we review the in vivo MNH preclinical studies, discussing results of the last two decades with emphasis on safety as a clinical criteria, the need for low-field nano-heaters and noninvasive thermal dosimetry, and the state of the art of computational modeling for treatment planning using MNH. Limitations to more effective clinical use are discussed, together with suggestions for future directions, such as the development of ultrasound-based, computed tomography-based or magnetic nanoparticle-based thermometry to achieve greater impact on clinical translation of MNH.

A review on numerical modeling for magnetic nanoparticle hyperthermia: Progress and challenges

Recent progress in nanotechnology has advanced the development of magnetic nanoparticle (MNP) hyperthermia as a potential therapeutic platform for treating diseases. Due to the challenges in reliably predicting the spatiotemporal distribution of temperature in the living tissue during the therapy of MNP hyperthermia, critical for ensuring the safety as well as efficacy of the therapy, the development of effective and reliable numerical models is warranted. This article provides a comprehensive review on the various mathematical methods for determining specific loss power (SLP), a parameter used to quantify the heat generation capability of MNPs, as well as bio-heat models for predicting heat transfer phenomena and temperature distribution in living tissue upon the application of MNP hyperthermia. This article also discusses potential applications of the bio-heat models of MNP hyperthermia for therapeutic purposes, particularly for cancer treatment, along with their limitations that could be overcome.