Our purpose of this study was to present simulation and experimental studies on magnetic hyperthermia (MH) with use of an alternating magnetic field (AMF) and superparamagnetic iron oxide nanoparticles (Resovist®). In the simulation studies, the energy dissipation (P) and temperature rise rate (∆T/∆t) were computed under various conditions by use of the probability density function of the particle size distribution based on a log-normal distribution. P and ∆T/∆t and their dependence on the frequency of the AMF (f) largely depended on the particle size of Resovist®. P and ∆T/∆t reached maximum at a diameter of ~24 nm, and were proportional to the amplitude of the AMF (H (0)) raised to a power of ~2.0. In the experimental studies, we made a device for generating an AMF, and measured the temperature rise under various concentrations of Resovist®, H (0), and f. The temperature rise at 10 min after the start of heating was linearly proportional to the concentration of Resovist®, and proportional to H (0) raised to a power of ~2.4, which was slightly greater than that expected from the simulation studies. There was a tendency for the temperature rise to saturate with increasing f. In conclusion, this study will be useful for investigating the feasibility of MH with Resovist® and optimizing the parameters for it.
ABSTRACT. Our aim was to assess the protective effect of hydrogen-rich water against cisplatin-induced nephrotoxicity in rats using dynamic contrast-enhanced CT (DCE-CT). DCE-CT studies were performed in 30 rats (8 weeks old) on days 0, 2, 4 and 7 using multidetector row CT. The rats were divided into three groups: a control group (n 56) with free access to standard water and without cisplatin injection, a non-treatment group (n 512) with free access to standard water and injected with cisplatin (3.6 mg kg -1 body weight) intraperitoneally on day 0 and a treatment group (n 512) with free access to hydrogen-rich water starting from 7 days before cisplatin injection. The contrast clearance per unit renal volume (K 1 ) was estimated from the DCE-CT data using the Patlak model. The contrast clearance of the entire kidney (K) was obtained by multiplying K 1 by the renal volume. The serum creatinine level was also measured on day 7. The K 1 and K values normalised by those on day 0 in the treatment group were significantly greater than those in the non-treatment group on days 2, 4 and 7. There were no significant differences in the normalised K value between the treatment and control groups on days 2 and 7. The serum creatinine level in the treatment group was significantly lower than that in the non-treatment group and was not significantly different from that in the control group. This study demonstrated that hydrogen-rich water ameliorates renal dysfunction due to cisplatin-induced nephrotoxicity in rats.
BOLD MRI may be useful for demonstrating the change in R2 in CP-induced nephrotoxicity in rats. The changes in the CP+HW group were suspected to be due to a reduction of cytotoxic oxygen radicals.
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