Hideyuki Hirazawa

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.

Development of Ti-Coated Ferromagnetic Needle, Adaptable for Ablation Cancer Therapy by High-Frequency Induction Heating

To develop a novel ablation therapy for human solid cancer, the heating properties of a ferromagnetic carbon steel rod and a prototype Ti-coated needle using this carbon steel rod, were investigated in several high-frequency outputs at 300 kHz. In the former, the heating property was drastically different among the three inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction as a result of the shape magnetic anisotropy. However, the effect of the inclination angles was completely eliminated in the latter. It is considered that the complete non-oriented heating property relative to the magnetic flux direction allows the precise control of the ablation temperature during minimally invasive thermotherapy without a lead-wire connected to a fiber-optic thermometer. This newly designed Ti-coated device will be suitable for clinical use combined with its superior biocompatibility for ablation treatments using high-frequency induction heating.

Heat generation properties in AC magnetic field for composite powder material of the Y3Fe5O12–nSiC system prepared by reverse coprecipitation method

Composite powder material of the Y3Fe5O12–nSiC system was synthesized by a reverse coprecipitation method to study its heat generation property in an AC magnetic field. For Y3Fe5O12 (n = 0), the maximum heat generation ability of 0.45 W·g−1 in an AC magnetic field (370 kHz, 1.77 kA·m−1) was obtained for the sample calcined at 1100 °C. The SiC addition helped to suppress the particle growth for Y3Fe5O12 at the calcination temperature. The heat generation ability was improved by the addition of the SiC powder, and the maximum value of 0.93 W·g−1 was obtained for the n = 0.3 sample calcined at 1250 °C. The heat generation ability and the hysteresis loss value were proportional to the cube of the magnetic field (H3). The heat generation ability (W·g−1) of the Y3Fe5O12–0.3SiC sample calcined at 1250 °C could be expressed by the equation 4.5×10−4 · f · H3 using the frequency f (kHz) and the magnetic field H (kA·m−1).

Heat generation ability in AC magnetic field of MgAlxFe2-xO4 ferrite powder prepared by sol-gel method

Al substituted MgAlXFe2-XO4 that have high heat generation ability in the AC magnetic field was obtained by Sol-Gel method. The heat generation ability was improved by Al3+ substitution, the highest heat generation property (ΔT = 127.2°C) was confirmed for X = 0.25 sample. This high heat generation ability was depended on hysteresis loss value, the hysteresis loss for X = 0.25 samples were significantly increased in the AC magnetic field.

Heat Generation and Transfer Behaviors of Ti-Coated Carbon Steel Rod Adaptable for Ablation Therapy of Oral Cancer

For the purpose of developing a novel ablation therapy for oral cancer, the heat generation and transfer properties of a Ti-coated carbon steel rod with 20-mm length and 1.8-mm outer diameter were investigated by means of a high-frequency induction technique at 300 kHz. The heat generation measurement performed using water (15 mL) revealed that the difference of the inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction only slightly affects the heating behavior, exhibiting the overlapped temperature curves during an induction time of 1200 s. These results suggest that the effect of the shape magnetic anisotropy is almost eliminated, being convenient for the precise control of the ablation temperature in clinical use. In the experiments utilizing a tissue-mimicking phantom, the heat transfer concentrically occurred in the lateral direction for both the planar surface and a 10-mm deep cross-section. However, the former exhibited a considerably lower increase in temperature (ΔT), probably due to the effect of heat dissipation to the ambient air. No significant heat transfer was found to occur to the lower side of the inserted Ti-coated carbon steel rod, which is situated in the longitudinal direction.

An Overview of Investigation for Ferrite Magnetic Nanomaterial

In recent time, interest to ferrite magnetic nanomaterials has considerably grown mainly due to their much promising medical and biological applications. The spinel ferrite powder samples having high heat generation ability in AC magnetic field was studied for application to hyperthermia treatment of cancer tumor. These properties of ferrites are strongly depending on their chemical composition, ion distribution, spin orientation and method of preparation in general and crystal structure in particular nature of the material. In this study, several samples of ferrite magnetic structures were investigated by neutron diffraction. The explanation of the mechanism to occurs the heat generation ability in the magnetic materials and the electronic and magnetic states of ferrite-spinel – type structures were theoretically defined by the first-principles calculations within the framework of DFT.

Heat Generation Ability in AC Magnetic Field for Y3Fe5O12-based Garnet Ferrite

The Y3Fe5O12-based ferrite, i.e., Y3-XGdXFe5O12 system was synthesized using a reverse coprecipitation method for application of new thermal coagulation therapy using an AC magnetic field for the treatment of cancerous tissues. The mixed phase of the Y3Fe5O12-type orthorhombic and cubic materials without any impurities were obtained for this systems calcined at low temperature in XRD results. However the orthorhombic phase almost disappeared by the calcination at 1150 °C or higher temperature for all the X samples. The calcination temperature strongly influenced the heat generation ability. The maximum heat generation ability (ΔT = 40-63°C, 370kHz, 1.77kA/m) was obtained for the powder materials sintered at 1100 °C for the Y3-XGdXFe5O12 system. The particle growth with the formation of the cubic single phase strongly influenced to the heat generation.