Medical Implant Communication Service Research Articles

An implantable wireless optogenetic stimulation system for peripheral nerve control.

An implantable wireless optogenetic stimulation system with an LED-based optical stimulation cuff electrode was developed for peripheral nerve control. The proposed system consisted of a battery-powered optical cuff electrode, optical stimulation controller, and wireless communication system. The optical cuff electrode had a polydimethylsiloxane (PDMS) structure was designed to illuminate the entire sciatic nerve. The wireless communication system was designed to comply with medical implant communication service (MICS) regulations. To evaluate the proposed system, optogenetic stimulation was performed in optogenetic transgenic mice (Thy1::ChR2). The optical cuff electrode was implanted on the sciatic nerve, and movement was elicited during optical stimulation. The experimental results show that ankle movement can be generated wirelessly using optical stimulation pulse parameters.

Comparison of Implantable Antennas for Cardiovascular Patients

Implantable device cardiac observation (ICDO) such as pacemaker requires communication with medical devices outside the body in order to monitor or control the parameters of the organ it is supporting. Three types of implantable antennas have been investigated to determine their performances on two patient conditions: normal and hyperglycemia. Folded dipole, serpentine microstrip, and waffle-type Planar Inverted-F (PIFA) antennas are operated in the 402-405 MHz, which is medical implant communication services (MICS) band. Detailed analysis of the design issues of the antennas and comparative results of simulations and measurements are presented.

MO‐F‐CAMPUS‐J‐02: Human Implanted Micro Bio Chip for Real‐Time Atrial Fibrillation Monitoring with Wireless Power Transmission

Purpose:There are numerous medical problems whose treatment requires the constant monitoring of vital signs from several body organs. In this study, a micro‐sized implantable electrocardiogram (ECG) sensor for personal heart disease monitoring was developed, as such devices generally provide a high diagnostic yield.Methods:An op‐amp amplifies an input electrical potential to the level desired by the user and produces an output potential augmented to this intended level. For this study an instrumentation amplifier was fabricated using op‐amps and configured to amplify micro‐fine ECG signals by a factor of about 100 using a band‐pass filter (BPF). The proposed ECG sensor has a current consumption of about 11 mA and a noise generation inversely proportional to the length of the wireless communication antenna inside the sensor. The packaging materials selected must be biocompatible to avoid causing inflammation or necrosis of human tissues. In addition, a near‐field wireless power transmission system and the medical Implant Communication Service (MICS) was used as a communications and power protocol. MICS operates in the frequency range of 402–405 MHz and is normally used for communication between body‐worn monitoring systems and implants.Results:A pig was used as a sensor‐implanted animal model because the animal's physiological characteristics are similar to those of humans. An incision was made between the left 5th–7th ribs and separated using blunt dissection to a depth of 4 mm under the skin. From the experiments, we successfully monitor the ECG with wireless communication and wireless power transmission.Conclusion:This study demonstrated that the use of a quasi‐permanentECG employing a double loop coil‐shaped magnetic resonance‐type wireless power transmission system sensor eliminates the need for surgical replacement.

A 1.3 mW low-IF, current-reuse, and current-bleeding RF front-end for the MICS band with sensitivity of -97 dbm

A low-power, low-intermediate frequency (IF) radio frequency (RF) front-end, including low-noise amplifier (LNA) and mixer for the medical implant communications service (MICS) RF band, is presented. The frequencies of LNA and mixer range from 402 MHz to 405 MHz, while the IF of the mixer is 450 KHz. Current-reuse, back-gate coupling, current-bleeding, and feedback circuit design techniques are utilized in the LNA design to achieve 10 dB of gain and the required noise figure (NF) under the low power consumption of 0.94 mW. By contrast, the Gilbert-type mixer generates 20 dB of conversion gain by using current-reuse, back-gate coupling, and current-bleeding techniques. The front-end is operated using a 1.8 V power supply and is capable of achieving a -97 dBm sensitivity using quadrature phase shift keying modulation while consuming 1.3 mW. The proposed front-end is implemented in TSMC 0.18 μm CMOS process with a total area of 1.4 mm × 1.2 mm. The gain enhancement technique has been substantially optimized compared with previous works and measurement results indicate that the front-end obtains the highest figure of merit compared with previous works.

Biotelemetry and Wireless Powering for Leadless Pacemaker Systems

In this letter, we address the telemetry and wireless powering problems associated with the recently invented leadless pacemaker. To overcome the telemetry problem, we propose a conformal spiral type Implantable antenna at Medical Implanted Communication Service (MICS) band. In addition, we also apply the recently proposed midfield wireless power transfer (WPT) technique at 1.5 GHz to avoid the bulky energy storage component. We simulate and experimentally measure the performance of the implantable antenna by using porcine heart tissue. Our research shows that, the implantable antenna and wireless power transfer scheme can be implemented in a leadless pacemaker without any significant coupling between them.

A 0.33 nJ/bit IEEE802.15.6/Proprietary MICS/ISM Wireless Transceiver With Scalable Data Rate for Medical Implantable Applications.

This paper presents an ultra-low power wireless transceiver specialized for but not limited to medical implantable applications. It operates at the 402-405-MHz medical implant communication service band, and also supports the 420-450-MHz industrial, scientific, and medical band. Being IEEE 802.15.6 standard compliant with additional proprietary modes, this highly configurable transceiver achieves date rates from 11kb/s to 4.5 Mb/s, which covers the requirements of conventional implantable applications. The phase-locked loop-based transmitter architecture is adopted to support various modulation schemes with limited power budget. The zero-IF receiver has programmable gain and bandwidth to accommodate different operation modes. Fabricated in 40-nm CMOS technology with 1-V supply, this transceiver only consumes 1.78 mW for transmission and 1.49 mW for reception. The ultra-low power consumption together with the 15.6-compliant performance in term of modulation accuracy, sensitivity, and interference robustness make this transceiver competent for various implantable applications.

Miniaturized Dual-Band Omnidirectional Antenna for Body Area Network Basestations

Challenges arising from body effect in design of implant and on-body antennas has dominated body area network (BAN) basestation antenna design research. However, design of an efficient basestation antenna in a compact size is also a challenge. This letter presents a miniaturized omnidirectional antenna in two bands of 403.5 MHz for medical implant communication services (MICS) and 2.45 GHz for industrial, scientific, and medical (ISM) applications. The antenna consists of two stacked center-fed circular patch over a circular ground plane. The upper and lower patches resonate in MICS and ISM bands, respectively. Each patch is loaded with two vias for miniaturization. The achieved miniaturization factors are 6.3 and 5.1 for MICS and ISM bands, respectively. Since the TM010-mode is excited, the pattern is omnidirectional with a null in broadside. The measurement results show a good agreement with the simulation in terms of reflection coefficient and radiation pattern.

A NOVEL RECONFIGURABLE SPIRAL-SHAPED MONOPOLE ANTENNA FOR BIOMEDICAL APPLICATIONS

In this paper, a new reconfigurable antenna is introduced. This antenna is a printed spiral- shaped monopole antenna with a compact structure. By embedding microwave switches in the structure of the antenna, different resonance frequencies can be achieved in different states of the switches. The introduced antenna is capable to cover two standard frequency bands for biomedical applications, i.e., Medical Implant Communication Service (MICS) and Industrial, Scientific and Medicine (ISM) bands. MICS band covers 402 MHz to 406 MHz and ISM covers 2.4 GHz to 2.5 GHz frequency range. The proposed antenna has a compact size of 32 mm × 50. 3m m× 1. 8 mm, and it is fabricated on an FR4 substrate. The measurement results are in a good agreement with the simulations.

A Subthreshold Low-Voltage Low-Phase-Noise CMOS LC-VCO with Resistive Biasing

This paper presents a low-phase-noise LC voltage-controlled oscillator (LC-VCO) with top resistive biasing in subthreshold region. The subthreshold LC-VCO has low-power and low-phase-noise due to its high transconductance efficiency and low gate bias condition. The top resistive biasing has more benefit with the feature of phase noise than MOS current source since it can support the low-noise characteristics and large output swing. The LC-VCO designed in 130-nm CMOS process with 0.7-V supply voltage achieves phase noise of -116 dBc/Hz at 200 kHz offset with tuning range of 398 MHz to 408 MHz covering medical implant communication service (MICS) band.

Experimental Path Loss Models for In-Body Communications Within 2.36-2.5 GHz.

Biomedical implantable sensors transmitting a variety of physiological signals have been proven very useful in the management of chronic diseases. Currently, the vast majority of these in-body wireless sensors communicate in frequencies below 1GHz. Although the radio propagation losses through biological tissues may be lower in such frequencies, e.g., the medical implant communication services band of 402 to 405MHz, the maximal channel bandwidths allowed therein constrain the implantable devices to low data rate transmissions. Novel and more sophisticated wireless in-body sensors and actuators may require higher data rate communication interfaces. Therefore, the radio spectrum above 1GHz for the use of wearable medical sensing applications should be considered for in-body applications too. Wider channel bandwidths and smaller antenna sizes may be obtained in frequency bands above 1GHz at the expense of larger propagation losses. Therefore, in this paper, we present a phantom-based radio propagation study for the frequency bands of 2360 to 2400MHz, which has been set aside for wearable body area network nodes, and the industrial, scientific, medical band of 2400 to 2483.5MHz. Three different channel scenarios were considered for the propagation measurements: in-body to in-body, in-body to on-body, and in-body to off-body. We provide for the first time path loss formulas for all these cases.

Standard of medical implant communication service

Medical implant communication service (MICS) is a standardized short-range wireless communication with ultra low power consumption applied for medical implant devices,which has been widely used all over the world.It is necessary to establish a unified international MICS standard.This paper details ITU-R SA.1346 standard from four aspects of technical parameters,compatibility,anti-interference methods and reliability of data transmission,and introduces the applications of MICS standard in Europe and America.Furthermore,comparison and analysis of the technical criteria in the above areas is conducted. Key words: Medical implant devices; Standard of communication service; Programmer; Wireless communication link

Design and implementation of a wireless medical system prototype for implantable applications

The design, implementation and testing of a wireless medical system (WMS) for continuous monitoring of biological parameters are presented in this paper. Special emphasis has been made on the implantable unit prototype. The proposed system consists of three main sections: implantable medical device (IMD), base station (BS) and graphical user interface. The IMD and BS communicate through an RF link that operates in both the industrial, scientific and medical (ISM, at 2.4---2.48 GHz) and the medical implantable communication service (MICS, at 402---405 MHz) bands. The IMD and BS are based on two commercially-available ultra-low power integrated circuits: a mixed-signal microcontroller and a medical implantable radio transceiver. A comprehensive explanation of the main design issues and implementation challenges is presented. The details regarding the analog front-end functionality, a low-power-oriented algorithm, an analysis of power consumption versus lifetime and a customized operating mode for power optimization are explained. The main considerations for link budget calculations in implantable applications are discussed. A test bench designed to emulate real conditions is used to verify the functionality of the WMS showing successful communication up to 2.1 m range with a data rate of 200 Kbps. The IMD works from a 3 V power supply with an average current consumption of 0.572 mA (including RF transmission) in continuous operation. This allows a 2 year IMD lifetime in periodic operation (for a 350 mAh battery), delivering 1 h of information per day.

Compact slotted semi‐circular antenna for implantable medical devices

A novel, compact, semi-circular, implantable, planar-inverted-F antenna (PIFA) is presented for the medical implant communications services (MICSs) band (402–405 MHz). By cutting three arc-shaped slots in a semi-circular patch, the proposed antenna can obtain effective size reduction. The total volume of the proposed antenna, including substrate and superstrate, is about 151 mm3. A bandwidth of 25 MHz is obtained at return loss of 10 dB. In addition, the radiation and specific absorption rate (SAR) performance of the antenna are examined and characterised.

Remote Powered Medical Implants for Telemonitoring

Chronic diseases like diabetes mellitus often require a permanent monitoring of vital signs. Especially the use of telemedicine will increase the quality of life for affected patients. Therefore, novel systems are necessary which are able to permanently detect and provide health status information. But these systems must not control patient's life and should work autonomously. For this purpose, intelligent medical implants are well qualified. This work describes a system for wireless power supply and communication with medical implant applications. Monitoring vital signs will create a big amount of data. Therefore, high data rates are necessary provided by high operating frequencies which in turn lead to electromagnetic far-field conditions. In this case, high attenuation losses due to the permittivity of the human body ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> have to be considered. Hence, high frequencies are not suitable for the transfer of energy into the human body. The presented concept is based on two different frequencies for power supply and data transmission. An independent development of both blocks is thereby possible. The power supply operates at a frequency of 13.56 MHz, using inductive coupling. Consequently, the human body does not affect the energy transfer. In contrast, the data transmission is operated at a frequency of the medical implant communication service (MICS) band. The elaborated system consists of a power supply unit, a data transmission unit, and a control unit. The implementation of the power supply and data transmission as well as associated theoretical basics are presented. Performed measurements demonstrate that the realized system is qualified for the use on human beings.

A Fast Settling Phase Modulator for Outphasing Transmitters in 65-nm CMOS

We present a phase modulator architecture with very fast settling time for use in high data-rate outphasing transmitters. The proposed design utilizes the phase-shifting capabilities of a resonant tank and the ability to separately control the circuit properties via its components. A prototype in 65-nm CMOS achieves 9 bits of effective resolution, with a fast settling time of less than five carrier cycles to within 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . The circuit is also tested as a standalone transmitter showing an error vector magnitude of less than 5% for 8-PSK modulation at maximum data rate of 240 Mb/s, meeting the Federal Communications Commission requirements for operation at the medical implant communication services band.

A fully integrated wireless system for intracranial direct cortical stimulation, real-time electrocorticography data transmission, and smart cage for wireless battery recharge.

Wireless transmission of cortical signals is an essential step to improve the safety of epilepsy procedures requiring seizure focus localization and to provide chronic recording of brain activity for Brain Computer Interface (BCI) applications. Our group developed a fully implantable and externally rechargeable device, able to provide wireless electrocorticographic (ECoG) recording and cortical stimulation (CS). The first prototype of a wireless multi-channel very low power ECoG system was custom-designed to be implanted on non-human primates. The device, named ECOGIW-16E, is housed in a compact hermetically sealed Polyether ether ketone (PEEK) enclosure, allowing seamless battery recharge. ECOGIW-16E is recharged in a wireless fashion using a special cage designed to facilitate the recharge process in monkeys and developed in accordance with guidelines for accommodation of animals by Council of Europe (ETS123). The inductively recharging cage is made up of nylon and provides a thoroughly novel experimental setting on freely moving animals. The combination of wireless cable-free ECoG and external seamless battery recharge solves the problems and shortcomings caused by the presence of cables leaving the skull, providing a safer and easier way to monitor patients and to perform ECoG recording on primates. Data transmission exploits the newly available Medical Implant Communication Service band (MICS): 402–405 MHz. ECOGIW-16E was implanted over the left sensorimotor cortex of a macaca fascicularis to assess the feasibility of wireless ECoG monitoring and brain mapping through CS. With this device, we were able to record the everyday life ECoG signal from a monkey and to deliver focal brain stimulation with movement elicitation.

Design of Implantable Rectangular Spiral Antenna for Wireless Biotelemetry in the MICS Band

For this study, we designed an implantable rectangular spiral antenna for medical biotelemetry in the Medical Implant Communications Service band (402 MHz to 405 MHz). The designed antenna has a U-shaped loop for impedance matching. The antenna impedance is easily adjusted by controlling the shape and length of the U-shaped loop. Significant design parameters were studied to understand their effects on the antenna performance. To verify the potential of the antenna for the desired applications, we fabricated a prototype and measured its performance in terms of the resonant characteristics and gain radiation patterns of the antenna. In the testing phase, the prototype antenna was embedded in human skin tissue-emulating gel, which was developed to simulate a real operation environment. The measured resonant characteristics show good agreement with the simulations, and the -10 dB frequency band is within the range of 398 MHz to 420 MHz. The antenna exhibits a maximum gain of -22.26 dBi and an antenna efficiency of 0.215%.

Genetic Algorithms for the Synthesis of Circular Microstrip Ring Antenna

Microstrip antennas synthesis is a demanding task; many of the equations involved in the process use various approximations due to the nonlinear properties and relations that govern the antenna synthesis. In This paper we tried to use genetic algorithm to design a circular microstrip ring that operates in a predefined frequency band (402 – 405 MHz) Medical Implant Communication Service Frequency Band. The methodology and procedures are presented, a presentation of the method is provided and an HFSS simulation of the antenna is made. Results are presented with guidelines for further future work

Design and in Vitro Test of a Differentially Fed Dual-Band Implantable Antenna Operating at MICS and ISM Bands

The design of a novel differentially fed dual-band implantable antenna operating at 402-405 MHz Medical Implant Communication Services (MICS) band and 2.4-2.5 GHz Industrial, Scientific, and Medical (ISM) band is introduced. The proposed implanted antennas are for both planar and flexible implantation scenarios. Biocompatible material parylene-C is adopted to cover the implanted antenna. The size of the proposed antennas including the encapsulation for planar and flexible case is 179.0 mm3 and 186.3 mm3 respectively. The Specific Absorption Rate (SAR) distribution and the radiation pattern at both frequencies induced by the implanted antenna are evaluated. The performance of the communication link between the implanted antenna and an external half-wavelength dipole at two resonant frequencies is also presented. In vitro test in minced pork is performed to test the reliability of the antenna in the real implantation cases.

Ultra‐low‐power wireless transmitter for neural prostheses with modified pulse position modulation

An ultra-low-power wireless transmitter for embedded bionic systems is proposed, which achieves 40 pJ/b energy efficiency and delivers 500 kb/s data using the medical implant communication service frequency band (402-405 MHz). It consumes a measured peak power of 200 µW from a 1.2 V supply while occupying an active area of 0.0016 mm(2) in a 130 nm technology. A modified pulse position modulation technique called saturated amplified signal is proposed and implemented, which can reduce the overall and per bit transferred power consumption of the transmitter while reducing the complexity of the transmitter architectures, and hence potentially shrinking the size of the implemented circuitry. The design is capable of being fully integrated on single-chip solutions for surgically implanted bionic systems, wearable devices and neural embedded systems.