摘要
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 (H<sub>0</sub>) 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 H<sub>s</sub> 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 (SLP<sub>qss</sub>) decreased with increasing H<sub>s</sub>. The plot of the SLP<sub>qss</sub> values against the position from the FFP became narrow as the gradient strength of the SMF (G<sub>s</sub>) increased. Conversely, it became broad as G<sub>s</sub> decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the H<sub>s</sub> and G<sub>s</sub> 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.
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 (H<sub>0</sub>) 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 H<sub>s</sub> 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 (SLP<sub>qss</sub>) decreased with increasing H<sub>s</sub>. The plot of the SLP<sub>qss</sub> values against the position from the FFP became narrow as the gradient strength of the SMF (G<sub>s</sub>) increased. Conversely, it became broad as G<sub>s</sub> decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the H<sub>s</sub> and G<sub>s</sub> 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.
作者
Kenya Murase
Kenya Murase(Department of Medical Physics and Engineering, Division of Medical Technology and Science, Faculty of Health Science, Graduate School of Medicine, Osaka University, Osaka, Japan)
