Hidetoshi Matsuki

Improvement of the Transcutaneous Energy Transmission System Utilizing Ferrite Cored Coils for Artificial Hearts

Heart transplantation is currently the best treatment for end-stage heart failure. There is a large disparity between the number of available donor hearts and the number of people who need them. Total artificial hearts and ventricular assist devices have been developed as alternatives to the transplantation. Percutaneous leads should be avoided in long-term implantations due to the risk of infection and the restraint on patients activities. Transcutaneous energy transmission systems transmit electric power across intact skin by electromagnetic induction with a pair of coils. Our system has thin ferrite cores, which increase the magnetic coupling factor and self-inductance. In addition MOSFET synchronous rectifier using a digital PLL technique can reduce forward voltage drops. These features result in high energy transmission efficiency. Also the core has a roll of magnetic shield. This effect made it possible to mount the synchronous rectifier circuit board on the back of the coil. In animal experiments, the output voltage of the TETS decreased when the primary coil shifted from the normal position. Local elevations of temperature at the ICs that consume relatively high power caused heat injuries. Also pressure necroses were seen in the circumference of the secondary coil.

Synchronous rectification for contactless power supply utilizing Mn–Zn ferrite core coils

Contactless power supply systems transmit electric power by electromagnetic induction with a pair of coils. The efficiency and the output voltage depend on parameters of coils. We studied the best parameter values that realize stable high efficiency contactless power supply. In the application with low output voltage, the voltage drop of the diodes becomes dominant power loss. A synchronous rectification was proposed as a solution of this problem. Our contactless power supply system for an artificial heart operates at 190kHz. We use planar coils with Mn–Zn ferrite cores. Highly stable output voltage and 88% maximum efficiency were realized.

Basic evaluation of signal transmission coil in transcutaneous magnetic telemetry system for artificial hearts

In implantable medical devices such as artificial hearts, it is important to communicate device control and monitoring signals across the skin for its stable operation. Using the signal transmission coil pairs we have proposed, we studied through measurements and experiments the best carrier frequency, based on the frequency characteristics of the L/C resonance circuit that inherits in the coil geometry.

Thermotherapy with metallic stent heated by external magnetic excitation

Stents are one method of treatment for stenosis of lumens organ from various causes. The cylindrical metallic stents are composed of alloy wire. After stents are implanted, however, the stenosis may recur due to a tumor or abscess again. It is particularly difficult to remove tumors or abscesses of the bile duct by surgical repair, because the duct is in a deep portion of the abdomen. We propose a noninvasive remedying method for tumors and abscesses by using thermotherapy with magnetically excited metallic stents. Currently, commercialized stents are not manufactured to allow for heating. In this paper, we studied the feasibility to heat the stents by external magnetic excitation for thermotherapeutic applications.

Examination to Improve Detection Accuracy of the Algorithm for Detecting Cracks on a Distribution Line

In this paper, the theory of nondestructive crack detection on distribution line is proposed. The algorithm to detect the cracks is devised, and the experimental machine using the algorithm was produced. As a result of the simulation and the laboratory experiment, the feasibility of the algorithm for crack detection was confirmed

Improvement of communication area for implantable signal transmission system with ferrite chip core

Transcutaneous power and signal transmission system are useful for artificial hearts. The signal transmission system is important to control the implanted device and to monitor the inside condition. They do not have lines penetrating through the skin. The signal transmission coils are set on the power transmission coils. We have proposed integrated power and signal transmission system utilizing eight-figure coils. Using the signal transmission coil pairs we have proposed, we studied through measurements and experiments the communication area for implantable signal transmission system with a ferrite chip core.

Thermotherapy With Metallic Stent Excited by the Magnetic Field

Stents are one method of treatment for stenosis of lumens organ from various causes. The cylindrical metallic stents are composed of alloy wire. After stents are implanted, however, the stenosis may recur due to a tumor or abscess again. It is particularly difficult to remove tumors or abscesses of the bile duct by surgical repair, because the duct is in a deep portion of the abdomen. We propose a noninvasive remedying method for tumors and abscesses by using thermotherapy with magnetically excited metallic stents. Currently, clinical stents are not manufactured to allow for heating. In this paper, we made experimental stents by magnetic shunt steel to heat the stents and control the heat of stents by external magnetic excitation for thermotherapeutic applications

Miniaturization of Micro Implantable Devices With Thermosensitive Ferrite for Soft-Heating Hyperthermia

The soft heating method is one technique utilized in hyperthermia treatment. The heater that consists of thermosensitive ferrite is implanted into the body, and heated by high-frequency magnetic field. This study applies the soft heating method. A complex type of heater composed of thermosensitive ferrite wound on a metallic ring is created. This complex type of heater produces heat due to losses of hysteresis and inductive current than thermosensitive ferrite alone. Further, this heater can control the temperature of the heater by using the Curie-point. For this technique, it is necessary to miniaturize the heater and provide safety high performance. We applied the method of miniaturization to plating. The effect of plating is examined. As a result, we have approximated to the optimal thickness of the metallic ring.

Heat Element of Magnetic Hyperthermia in Mouse Melanoma Model

The soft-heating method is one kind of heating technique of hyperthermia. The feature of this method is to use thermosensitive magnetic material as the heat element. This means the heat element can control the temperature automatically, referring the Curie-point of the thermosensitive ferrite. The heat element consists of a thermosensitive ferrite and metal ring. The purpose of the metal ring wrapped to ferrite is to increase heat quantity compared with that of ferrite alone. In this study, the effect of the heat element in mouse tumor model (B-16 melanoma) is examined. As a result, the tumors of mice were locally heated to the point at which tumor is necrotized in the condition of 200 kHz-6 mT

Evaluation of damage in DNA molecules caused by very-low-frequency magnetic fields using bacterial cells

The effect of intermediate frequency magnetic fields or, very-low-frequency magnetic fields (VLFMF) on living biological cells was investigated using a highly sensitive mutagenesis assay method. A bacterial gene expression system for mutation repair (umu system) was used for the sensitive evaluation of damage in DNA molecules. Salmonella typhimurium TA1535 (pSK1002) were exposed to VLFMF (20 kHz and 600 μT) in a specially designed magnetic field loading chamber. The experiment results showed the possibility of applying the umu assay for sensitive and effective evaluation of damage in DNA molecules. No effects from exposure to 20kHz and 600 μT magnetic fields in terms of damage in DNA molecules were observed.