Magnetic nanoparticle (MNP) hyperthermia ablates malignant cells by heating the region of interest when MNPs are subjected to an external alternating magnetic field. The energy density to be dissipated into heat, and consequently the temperature profile during treatment, depends on the distribution of MNPs within the tumoral region. This paper uses numerical models to evaluate the temporal and spatial temperature distributions inside a tumor when intratumoral injection of MNPs is considered. To this end, the theories of mass transfer and diffusion in interstitial tissue are combined with Rosensweig’s theory and Pennes bio-heat transfer equation, and the finite element method is used for analyzing the temperature field under different scenarios. Simulation results demonstrate that the treatment temperature field strongly depends on factors, such as the injection method, particle size, injection concentration and injection dose. However, the maximal temperature reached during hyperthermia and the effective treatment area are difficult to control. In order to obtain better treatment effects, this paper investigates a solution that uses a kind of material with low Curie temperature and the results show that the effective treatment area of hyperthermia can be significantly improved using this type of MNP.
Magnetic nanoparticle (MNP) hyperthermia is a promising emerging therapy for cancer treatment that is minimally invasive and has been successfully used to treat different types of tumors. The power dissipation of MNPs, which is one of the most important factors during a hyperthermia treatment, is determined by the properties of MNPs and characteristics of the magnetic field. This paper proposes a method based on the finite element analysis for determining the value of the power dissipation of particles (PDP) that can maximize the average temperature of the tumor during treatment and at the same time guarantee that the maximum temperature is within the therapeutic range. The application of the critical PDP value can improve the effectiveness of the treatment since it increases the average temperature in the tumor region while limiting the damage to the healthy tissue that surrounds it. After the critical PDP is determined for a specific model, it is shown how the properties of the MNPs can be chosen to achieve the desired PDP value. The transient behavior of the temperature distribution for two different models considering blood vessels is analyzed as a case study, showing that the presence of a blood vessel inside the tumor region can significantly decrease the uniformity of the temperature field and also increase the treatment duration given its cooling effects. To present a solution that does not depend upon a good model of the tumor region, an alternative method that uses MNPs with low Curie temperature is proposed, given the temperature self-regulating properties of such MNPs. The results demonstrate that the uniformity of the temperature field can be significantly increased by combining the optimization procedure proposed in this paper with the use of low-Curie-temperature MNPs.
Treatment temperature distribution is a crucial factor for magnetic hyperthermia, since it directly determines the treatment effect related to the apoptosis situation of malignant cells. The shape of magnetic nanoparticles (MNPs) is one of many factors that can affect the treatment temperature during therapy. This paper conducts a comparative study on three different shapes of MNPs by considering the effective area percentage of treatment temperature distribution. The treatment temperature for a proposed model is predicted by solving bio-heat transfer equations, which take the power dissipation of MNPs as the input and consider a temperature-dependent blood perfusion rate in these equations at the same time. The simulation results demonstrate that the treatment temperature distribution can be effectively improved when the temperature-dependent blood perfusion rate is used for the simulation with respect to a constant case. In addition, the MNPs with higher regular shape can lead to a better result than a lower case in the treatment temperature distribution when the same condition is considered for therapy.
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