Transcutaneous Energy Transmission Research Articles

補助人工心臓用体外結合型経皮エネルギー伝送システム

補助人工心臓用体外結合型経皮エネルギー伝送システム

フレキシブルコイルを用いた人工心臓用磁界共振結合経皮電力伝送システムのファントムによる評価

A conventional power supply method using a drive line for a ventricular assist device causes infection diseases, which decreases patient’s quality of life and survival rate. A possible solution is to use a transcutaneous energy transmission system utilizing electromagnetic induction. However, it is necessary for the coil to be located on the body surface accurately because of short transmission distance. In order to avoid infection diseases as well as increase the transmission distance, we proposed the new system utilizing magnetic resonant coupling that embedded flexible coils into clothes to transfer energy. In this paper, we evaluated the influence of the electric characteristics of the human body on the transmission efficiency by using both phantom and pork. The measured transmission efficiency with a gap of 30 mm was 67 % in phantom and 70 % in pork while that in air was 80 %.

Analysis of specific absorption rate and internal electric field in human biological tissues surrounding an air-core coil-type transcutaneous energy transmission transformer.

In this study, we analyzed the internal electric field E and specific absorption rate (SAR) of human biological tissues surrounding an air-core coil transcutaneous energy transmission transformer. Using an electromagnetic simulator, we created a model of human biological tissues consisting of a dry skin, wet skin, fat, muscle, and cortical bone. A primary coil was placed on the surface of the skin, and a secondary coil was located subcutaneously inside the body. The E and SAR values for the model representing a 34-year-old male subject were analyzed using electrical frequencies of 0.3-1.5MHz. The transmitting power was 15W, and the load resistance was 38.4Ω. The results showed that the E values were below the International Commission on Non-ionizing Radiation Protection (ICNIRP) limit for the general public exposure between the frequencies of 0.9 and 1.5MHz, and SAR values were well below the limit prescribed by the ICNIRP for the general public exposure between the frequencies of 0.3 and 1.2MHz.

Detecting Malposition of Coil Couple for Transcutaneous Energy Transmission.

Transcutaneous energy transmission technology based on coil coupling is widely required for various wireless powering implanted devices in human body. However, the coupling performance is commonly affected by malposition between coils in practice. It is difficult for users to know the actual position of the implanted receiver coil (RC) and how to realign the transmitter coil (TC) outside the body. This article proposes a detecting method of coil-coupling malposition based on a sensing board with coil array fitted on the TC. In this article, the sensing system and the data processing algorithm separating the sensing coil (SC) signals induced by TC and RC currents, respectively, are introduced. Then, an analytical model formulating the induction effect between the RC and SCs is given. Inverse computation algorithms of the malposition based on the processed sensing data and the induction effect model are presented at last. The proposed method is validated by experiments simulating malposition both in distance and concentricity on an actual coil couple. The results show that the sensing system can provide accurate parameterized guide for users to adjust the installation of the TC for good energy transmission performance.

Influence of the Coil Inductance on the Transcutaneous Energy Transmission using the Flexible Coil

Influence of the Coil Inductance on the Transcutaneous Energy Transmission using the Flexible Coil

Externally Coupled Transcutaneous Energy Transmission System for VAD: Measurement of Conducted Emission at the Transmitting Power of 15 Watt

Externally Coupled Transcutaneous Energy Transmission System for VAD: Measurement of Conducted Emission at the Transmitting Power of 15 Watt

A study of the asymmetry effect of the coils for the transcutaneous energy transmission system

A study of the asymmetry effect of the coils for the transcutaneous energy transmission system

Primary side control of load voltage for transcutaneous energy transmission.

Transcutaneous energy transmission (TET) is considered as a good way to wirelessly power the implanted devices in human bodies. The load voltage provided from the TET to the implanted device should be kept stable to ensure the device working well, which however, is easily affected by the required power variation for different body movements and coil-couple malposition accompanying skin peristalsis. Commonly, the load voltage applied onto the device should be measured and feedback for power is regulated by implanting sensing and communication units into the body, which causes additional energy cost, increased size and weight of the implanted device. This paper takes the TET for artificial heart as an example to propose a novel primary side control method of the load voltage for TET, which does not require any additional implanted components. In the method, sensing coils are used to measure the malposition between the transmitter coil (TC) and receiver coil, and the magnitude of the TC current outside the human body. The measurement results are used to estimate the load voltage inside the body through calculation, whose value provide a base to develop a PI control system to regulate the input power of TET for the load voltage stability. The proposed method is experimentally validated on an actual TET for artificial heart by varying its load in a wide range under serious coil-couple malposition. With applying the primary side control, the variation of the load voltage is reduced to only 25 % of that without the control.

Influence of Angular Coil Displacements on Effectiveness of Wireless Transcutaneous Inductive Energy Transmission

The effect of angular displacements on wireless transcutaneous inductive energy transmission was studied using computational modeling. It is shown that for a geometry characteristic of transcutaneous energy transmission (distance between centers of flat coils less than the radius of the coils, angular displacement in the range of 0-30°), the angular displacement can lead to an increase in transmitted power. Therefore, it is essential to develop methods of preventing transmission of excessive power to the receiver portion of a wireless energy transmission system to avoid overheating of implanted components.

経皮エネルギー伝送の三相交流化による放射磁界低減

経皮エネルギー伝送の三相交流化による放射磁界低減

体内埋込型人工心臓用経皮エネルギー伝送システム

Transcutaneous energy transmission is a noninvasive method for supplying power to an implantable artificial heart. However, it is necessary to continue energy transmission using a transcutaneous transformer during bathing because an implantable battery is not yet commercially available. In this study, we evaluated the electromagnetic safety, transmission efficiency, and temperature rise of two types of transformers (air-core-flat type and externally coupled type) immersed in various conductive liquids, with the assumption of bathing and sweating. It was found that, as the liquid conductivity increased, the transmission efficiency decreased; and as the transmission frequency increased, the efficiency decreased significantly. When the transformers were immersed in 0.9% NaCl solution with the assumption of bathing and sweating, the transmission efficiency of each transformer was higher than 94.4% for a transmission frequency of 400 kHz, and the temperature rise was less than 0.3°C. These findings indicate that our transcutaneous transformers can transmit energy to artificial hearts even when immersed in 0.9% NaCl solution.

Design and Evaluation of a Fully Implantable Control Unit for Blood Pumps.

As the number of donor hearts is limited while more and more patients suffer from end stage biventricular heart failure, Total Artificial Hearts become a promising alternative to conventional treatment. While pneumatic devices sufficiently supply the patients with blood flow, the patient's quality of life is limited by the percutaneous pressure lines and the size of the external control unit. This paper describes the development of the control unit of the ReinHeart, a fully implantable Total Artificial Heart. General requirements for any implantable control unit are defined from a technical and medical point of view: necessity of a Transcutaneous Energy Transmission, autonomous operation, safety, geometry, and efficiency. Based on the requirements, a prototype is designed; it incorporates a LiFePo4 battery pack with charger, a rectifier for transcutaneous energy transmission, the motor's driver electronics, and a microcontroller which monitors and controls all functions. In validation tests, the control unit demonstrated a stable operation on TET and battery supply and a safe switching from one supply to the other. The overall mean efficiency is 14% on TET and 22% on battery supply. The control unit is suitable for chronic animal trials of the ReinHeart.

Novel direct charging method of internal battery for Transcutaneous Energy Transmission System

Novel direct charging method of internal battery for Transcutaneous Energy Transmission System

電磁誘導による無線給電方式の現在と未来

電磁誘導による無線給電方式の現在と未来

Basic study of transcutaneous energy transmission system using direct or capacitive coupling electrode

Basic study of transcutaneous energy transmission system using direct or capacitive coupling electrode

System overview of the fully implantable destination therapy--ReinHeart-total artificial heart.

Owing to the lack of suitable allografts, the demand for long-term mechanical circulatory support in patients with biventricular end-stage heart failure is rising. Currently available Total Artificial Heart (TAH) systems consist of pump units with only limited durability, percutaneous tubes and bulky external equipment that limit the quality of life. Therefore we are focusing on the development of a fully implantable, highly durable destination therapy total artificial heart. The ReinHeart-TAH system consists of a passively filling pump unit driven by a low-wear linear drive between two artificial ventricles, an implantable control unit and a compliance chamber. The TAH is powered by a transcutaneous energy transmission system. The flow distribution inside the ventricles was analysed by fluid structure interaction simulation and particle image velocimetry measurements. Along with durability tests, the hydrodynamic performance and flow balance capability were evaluated in a mock circulation loop. Animal trials are ongoing. Based on fluid structure interaction simulation and particle image velocimetry, blood stagnation areas have been significantly reduced. In the mock circulation loop the ReinHeart-TAH generated a cardiac output of 5 l/min at an operating frequency of 120 bpm and an aortic pressure of 120/80 mmHg. The highly effective preload sensitivity of the passively filling ventricles allowed the sensorless integration of the Frank Starling mechanism. The ReinHeart-TAH effectively replaced the native heart's function in animals for up to 2 days. In vitro and in vivo testing showed a safe and effective function of the ReinHeart-TAH system. This has the potential to become an alternative to transplantation. However, before a first-in-man implant, chronic animal trials still have to be completed.

Safety considerations for wireless delivery of continuous power to implanted medical devices.

Wireless power systems for use with implants are referred to as transcutaneous energy transmission systems (TETS) and consist of an implanted secondary coil and an external primary coil along with supporting electronics. A TETS system could be used to power ventricular assist systems and eliminate driveline infections. There are both direct and indirect safety concerns that must be addressed when continuously transferring power through the skin. Direct safety concerns include thermal tissue damage caused by exposure to the electromagnetic fields, coil heating effects, and potential unwanted nerve stimulation. Indirect concerns are those caused by potential interference of the TETS system with other implanted devices. Wireless power systems are trending towards higher frequency operation. Understanding the limits for safe operation of a TETS system across a range of frequencies is important. A low frequency and a high frequency implementation are simulated to demonstrate the impact of this trend for a VAD application.

Novel Artificial Anal Sphincter System Based on Transcutaneous Energy Transmission System Tested in vivo

This paper proposes a novel artificial anal sphincter system (AASS) for severe fecal incontinence. The AASS is composed of an artificial anal sphincter (AAS), an external transcutaneous energy transmission system (TETS), and an external control device. The AAS is composed of a cuff, a micropump, a reservoir, and a remote control device. It is designed to be implanted into the body of the patient. The function of the AAS is to open and close the patient's natural anus. Patients suffering from loss of their natural sphincter lose rectal sensation and are thus unable to perceive imminent fecal incontinence. In order to restore rectal sensation, a pressure sensor in the AAS cuff is designed to detect pressure in the colon. The pressure reflects the present quantity of colon contents, allowing patients to control the AAS to open or close the anus according to the pressure. The TETS is designed to provide electrical energy to the implanted AAS without wire connections. The external control device is designed to receive the pressure information from the AAS and send the patient's command to the implanted device. This paper provides a thorough discussion of the design of the novel AASS and describes the performance of the AASS when tested in vivo on two Beagle dogs who were chosen to be the subjects for receiving the implant. The experimental results verified that the performance of the AASS met the functional requirements it was designed for; however, the trial also revealed some challenges to be further studied.

Optimization of Transcutaneous Energy Transmission Systems Suitable for Left Ventricular Assist Devices

Transcutaneous energy transmission systems (TETS) wirelessly transmit power through the skin. TETS is particularly desirable for ventricular assist devices (VAD), which currently require cables through the skin to power the implanted pump. Current implantable TETS systems are not optimized for high power VAD applications. Optimizing the inductive link of the TET system is a multi-parameter problem. Most current techniques to optimize the design simplify the problem by combining parameters leading to sub-optimal solutions. In this paper we present an optimization method using a genetic algorithm to handle a larger set of parameters, which leads to a more optimal design.

Energy Transmission System for an Artificial Heart

Transcutaneous energy transmission systems (TETSs) use electromagnetic induction to transfer power to an artificial heart. The aim of this study is to develop a TETS where the primary coil is located away from the body. In this case, a fluctuation in the relative position between the primary and secondary coils causes a large change in the output voltage. To stably drive an artificial heart, it is necessary to control the output voltage using feedback control. However, feedback control requires the use of an additional information transmission system in TET circuits. Therefore, we developed a novel method for reducing the fluctuation in the output voltage without using feedback control; this method involved uniformalizing the coupling magnetic coefficient k. As a result, the fluctuation in the output voltage was maintained to within 8.6V. These results suggest that fluctuation in the output voltage can be maintained at a sufficiently low value so as to stably drive an artificial heart without using feedback control.