Abstract
Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values estimated by this method under various diameters (D) of magnetic nanoparticles (MNPs) and amplitudes (H0) and frequencies (f) of an alternating magnetic field (AMF). In our method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically, in which the magnetic field strength at time t (H(t)) was assumed to be given by , with Hs being the strength of the SMF. We also investigated the SLP values in the case when the SMF with a field-free point (FFP) generated by two solenoid coils was used. The SLP value in the quasi steady state (SLPqss) decreased with increasing Hs. The plot of the SLPqss values against the position from the FFP became narrow as the gradient strength of the SMF (Gs) increased. Conversely, it became broad as Gs decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the Hs and Gs values, respectively. In conclusion, our method will be useful for estimating the SLP in the presence of both the AMF and SMF and for designing an effective local heating system for magnetic hyperthermia in order to reduce the risk of overheating surrounding healthy tissues.
Highlights
Hyperthermia is one of the promising approaches to cancer therapy [1] [2]
Our method will be useful for estimating the specific loss power (SLP) in the presence of both the alternating magnetic field (AMF) and static magnetic field (SMF) and for designing an effective local heating system for magnetic hyperthermia in order to reduce the risk of overheating surrounding healthy tissues
We presented a method for estimating the SLP in magnetic hyperthermia in the presence of both the AMF and SMF, which was derived by solving the magnetization relaxation equation of Shliomis [14] numerically
Summary
Hyperthermia is one of the promising approaches to cancer therapy [1] [2]. Hyperthermia with use of magnetic nanoparticles (MNPs) (magnetic hyperthermia) was developed in the 1950s [3] and is still under development in the effort to overcome the drawbacks in other hyperthermia modalities such as radiofrequency (RF)-capacitive hyperthermia and ultrasound hyperthermia [4] [5].MNPs generate heat in an alternating magnetic field (AMF) as a result of hysteresis and relaxational losses, which results in heating of the tissue in which MNPs accumulate [6]. With the development of precise methods for synthesizing functionalized MNPs [7], MNPs with functionalized surfaces, which have high specificity for tumor tissue, have been developed as heating elements for magnetic hyperthermia [8]. There is renewed interest in magnetic hyperthermia as a treatment modality for cancer, especially when it is combined with other, more traditional therapeutic approaches such as the co-delivery of anticancer drugs [10] or radiation therapy [11]. From these aspects, magnetic hyperthermia has received much recent attention
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