Takashi Naohara

Heating of ferrite powder by an AC magnetic field for local hyperthermia

To develop materials for achieving local hyperthermia, we investigate the heating of various ferrite and metal powders by applying an external AC magnetic field. In comparison with magnetite powder, which has often been used in previous experiments, Mg-ferrite powder is more applicable for achieving local hyperthermia.

Feasibility of chemohyperthermia with docetaxel-embedded magnetoliposomes as minimally invasive local treatment for cancer

Hyperthermia is a minimally invasive approach to cancer treatment, but it is difficult to heat only the tumor without damaging surrounding tissue. To solve this problem, we studied the effectiveness of chemohyperthermia with docetaxel‐embedded magnetoliposomes (DMLs) and an applied alternating current (AC) magnetic field. Human MKN45 gastric cancer cells were implanted in the hind limb of Balb‐c/nu/nu mice. Various concentrations of docetaxel‐embedded DMLs were injected into the tumors and exposed to an AC magnetic field (n = 6, each). For comparison with hyperthermia alone, magnetite‐loaded liposome (ML)‐injected tumors were exposed to an AC magnetic field. Furthermore, the results of DML without AC treatment and docetaxel diluted into PBS with AC treatment were also compared (n = 10, each). Tumor surface temperature was maintained between 42 and 43°C. Tumor volume was reduced in the DML group with a docetaxel concentration > 56.8 μg/ml, while a docetaxel concentration > 568.5 μg/ml was required for tumor reduction without hyperthermia. Statistically significant differences in tumor volume and survival rate were observed between the DML group exposed to the magnetic field and the other groups. The tumor disappeared in 3 mice in the DML group exposed to the magnetic field; 2 mice survived over 6 months after treatment, whereas all mice of the other groups died by 15 weeks. Histologically, hyperthermia with DML damaged tumor cells and DML diffused homogeneously. To the best of our knowledge, this is the first report to show that hyperthermia using chemotherapeutic agent‐embedded magnetoliposomes has an anticancer effect.

Development of a second-generation radiofrequency ablation using sintered MgFe2O4 needles and alternating magnetic field for human cancer therapy

Magnetic metal particles are known to induce heat energy under an alternating magnetic field (AMF). We developed a local tumor-heating device incorporating an MgFe(2)O(4) needle for the purpose of mild ablation for cancer treatment. A needle made from sintered MgFe(2)O(4) particles was embedded in the hepatic or breast tumors. Tumors were then heated by the energy dissipated from the needle exposed to an AMF. We sequentially evaluated histological changes, cellular activity of tumors, and the extent of thermal effect using nicotinamide adenine dinucleotide (NADH) diaphorase and terminal deoxynucleotidyl tranferase-mediated digoxigenin-DUTP nick-end labeling (TUNEL) staining. The mean temperature of the tumor tissue during heating was about 60 degrees C. Nuclei of the tumor cells became hyper-chromatin immediately after heating. The injured area spread progressively until 3 days after heating; when the area was surrounded by fibroblasts (meaning is not clear). Tumors disappeared after treatment without complications. This is the first time that the complete death of tumor cells has been realized by raising the tumor temperature above 60 degrees C using the heat generated by magnetic metal particles exposed to AMF. This device may be useful in the future for local hyperthemic treatment of human cancers.

Tumor local chemohyperthermia using docetaxel-embedded magnetoliposomes: Interaction of chemotherapy and hyperthermia.

Background and Aim:  We have studied and reported the usefulness of tumor local chemohyperthermia at a low‐grade temperature below 43°C with docetaxel‐embedded magnetoliposome (DML) and an applied alternating current magnetic field. However, the mechanisms of this treatment and the dynamics of the injected docetaxel were not investigated in our previous study. Thus, we investigated the interaction of chemotherapy and hyperthermia in the treated tumor.

The effect of metallic elements on the crystallization behavior of amorphous Fe-Si-B alloys

The crystallization behavior of amorphous Fe84-XSi6B10MX (M=Nb, Zr, V, or Cu) alloys was examined using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) with the aim of clarifying the effect of additional M elements. The compositional dependence of the first crystallization temperatureTx1 increased in the order of Zr > Nb > V; however, the addition of 1 at. pct Cu caused a decrease inTx1. Such an effect of the M elements on the thermal stability of an amorphous phase was interpreted in terms of the difference in the atomic size. These alloys were composed of a mixed structure ofα-Fe and amorphous phases after aging for 3.6 ks in the first exothermic temperature range. The addition of more than 3 at. pct Nb or Zr significantly affected the morphology and grain size of theα-Fe phase. However, their particles possessed dendritic morphology with a grain size of 0.1 to 0.3 µm, when the Nb or Zr content was less than 2 at. pct. Further addition of these elements brought about the formation of sphericalα-Fe particles. The average grain size, for instance, was as small as 20 nm in the aged alloy containing 6 at. pct Nb, which shows that a remarkable grain refinement occurs with increasing Nb content.

Repeated inductive heating using a sintered MgFe2O4 needle for minimally invasive local control in breast cancer therapy.

Purpose: This study investigated the efficacy of repeated thermotherapy for breast cancer utilising a novel sintered MgFe2O4 needle and alternating current (AC) magnetic field in xenograft animal models mimicking human breast cancer. Materials and methods: A sintered MgFe2O4 needle and an apparatus to apply an AC magnetic field were prepared for this study. Animals bearing BT-474 tumours (mean (±standard deviation) volume, 471 ± 153 mm3) were divided into four groups. A sintered MgFe2O4 needle (length, 5 mm) was placed in the centre of each tumour. An AC magnetic field (amplitude, 4 kA/m; 2 kW; 540 kHz) was applied for 10 min once, twice or three times for the first, second and third groups, respectively, and was not applied for the control group. Temperature during treatment and tumour volume 8 weeks after first treatment were assessed. Results: Maximum tumour temperature tended to increase in repeated-application groups: group 1, 59.2 ± 4°C; group 2, 58.9 ± 3.3°C and 61.2 ± 8.9°C for the first and second applications; and group 3, 60.4 ± 4.6°C, 62.1 ± 7.8°C and 71.1 ± 6.1°C for the first, second and third applications. Tumour volumes in control, groups 1, 2 and 3 at 8 weeks after treatment were 3633 ± 2478 mm3, 3240 ± 1031 mm3, 1252 ± 1289 mm3 and 0 mm3, respectively. Tumours were significantly smaller in group 3 than in the control and group 1 at 8 weeks. Conclusions: The efficacy of repeated inductive heating utilising a sintered MgFe2O4 needle was demonstrated. Thermotherapy using the present method may offer an effective non-surgical treatment for human breast cancer.

Novel tumor‐ablation device for liver tumors utilizing heat energy generated under an alternating magnetic field

Background and Aims:  We have developed a novel tumor‐ablation device for liver tumors utilizing heat energy induced by magnesium ferrite (MgFe2O4) particles under an alternating magnetic field (AMF) produced by electric currents. This novel device can repeatedly heat liver tumors at lower temperature than usual heating devices, such as radiofrequency ablation therapy, with slight infliction of pain. This study assesses its heating effect on rat liver tumors as local therapy.

Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr2Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe50Cr30Al20 alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility.

Heat generation ability in AC magnetic field of needle‐type Ti‐coated mild steel for ablation cancer therapy

Purpose – The purpose of this paper is to develop a ferromagnetic needle adaptable for a novel ablation cancer therapy; the heat generation ability of the mild steel rod embedded into the Ti‐tube having a different thickness was investigated in a high‐frequency output at 300 kHz.Design/methodology/approach – The outer diameter and length of the Ti‐tubes were 1.8 and 20 mm, respectively, while the inner diameter was varied from 1.6 to 0 mm. The mild steel rod was embedded in a Ti‐tube for preparing the needle‐type specimen. Their heat generation ability was examined by changing the inclination angle to the magnetic flux direction in a high‐frequency coil.Findings – When the thickness of the Ti surrounding the mild steel rod was as low as 0.1 mm, the heat generation ability was drastically different among the three inclination angles (θ=0°, 45°, and 90°) to the magnetic flux direction due to the effect of the shape‐induced magnetic anisotropy. However, the effect of the inclination angle was almost eliminat...

High-Heat Generation Ability in AC Magnetic Field for Ti Tube Filled with Ferrite Powder

Needle-type materials were studied for the application of thermal coagulation therapy in an AC magnetic field. We found that the Ti tube filled with ferrite powder as the core had a high heat generation ability in an AC magnetic field. Although the Ti tube without the ferrite powder or Ti rod showed poor heat generation abilities, the temperature was significantly increased by the existence of ferrite powder in the tube. In this case, the ferrite powder seems to improve the eddy loss for the Ti tube. The maximum heat generation ability was obtained for the Ti tube that contained MgFe2O4 powder in the examined Ti tube with some ferrites.