Wireless Medical Devices Research Articles

An ultra‐low‐power low‐noise amplifier using a combination of current reuse and self‐forward body bias techniques for biomedical applications

SummaryLow‐power low noise amplifiers (LNAs) are critical block in the radio frequency (RF) front‐end of medical device radiocommunications service (MedRadio) receivers for amplifying weak received signals while introducing minimal noise. Despite the inherently low transconductance of MOS transistors, it is possible to achieve low noise, high gain, and good linearity in low power LNAs. This paper presents a combination of techniques to realize an ultra‐low‐power LNA with a compact size and high performance. The proposed LNA utilizes multiple gm‐boosting and self‐forward body bias techniques, with certain transistors operating in weak inversion. Additionally, the Multi‐Objective Inclined Planes System Optimization algorithm is employed to determine the optimal values of the circuit components, thereby achieving the best compromise among the various performance parameters. The proposed LNA with buffer is designed and simulated using an 180 nm CMOS process over the frequency band of 0.3–1 GHz. Simulated results show that the proposed LNA achieves a gain of 19.6 dB, a noise figure of 5.1 dB, good input matching (S11 < −10 dB), and a third‐order intermodulation intercept point (IIP3) of 3.8 dBm. Additionally, it consumes 320 μW (without buffer) from a 1 V power supply, and the chip area is 235 μm × 372 μm. The simulated results demonstrate that the proposed ultra‐low power LNA is a promising candidate for biomedical applications.

A Low-Power Fully Differential Level-Crossing ADC Based on Single-Reference Comparator for Wireless Medical Implantable Devices

This paper introduces a low-power fully differential fixed window level-crossing analog-to-digital converter (LC-ADC) for wireless medical implantable devices. The LC-ADC could be an excellent candidate for low-power systems due to the reduction of sampling points for bio-potential signals. Different from existing fixed window LC-ADCs, which use a 1-bit DAC or scaler and two reference levels to move the input signal to the comparison window, a simplified scheme is proposed in which the DAC or scaler is removed and a single-reference level is used to create the comparison window. The proposed LC-ADC utilizes a single-reference comparator, which leads to a simplified implementation and significant reduction in power consumption and circuit area. In addition, using a single reference level and removing DAC, leads to a decrease in the complexity of the controlling logic. The proposed LC-ADC is simulated in 0.18[Formula: see text][Formula: see text]m CMOS technology. The simulation results achieve an effective number of bits (ENOB) of up to 6.5 bits with about 59–141 nW power consumption under 0.8[Formula: see text]V supply and input signal bandwidth from 5[Formula: see text]Hz to 4[Formula: see text]kHz.

A Variable-Gain Low-Noise Amplifier for MedRadio Band Applications

A variable-gain 0.18 μm Complementary Metal- Oxide-Semiconductor (CMOS) Low-Noise Amplifier (LNA) for Medical Device Radiocommunications Service (MedRadio) applications has been designed and verified through simulations in Cadence IC5 with Silterra’s C18G CMOS technology Process Design Kit. Unlike other MedRadio LNAs from previous works, this proposed LNA can vary its gain from just above 10 dB to nearly 30 dB. It consists of three stages; the input-matching stage, the interstage buffer, and the gain-varying stage. The input-matching stage provides an input impedance match and drives the initial gain of the LNA. The inter-stage buffer isolates the input-matching stage from the gain-varying stage. The overall gain of the LNA can be varied and is determined by the variable biasing of the driving transistors of the gainvarying stage. On post-layout simulations with a sourcefollower output buffer, this LNA exhibits a wide-ranging gain from 11.2 dB at 0.49 mW DC power consumption to 29.1 dB at 1.34 mW DC power consumption.

Computer-Aided Secure Access and Management of Wireless Medical Devices using Internet of Things and Biometric Technology

Computer-Aided Secure Access and Management of Wireless Medical Devices using Internet of Things and Biometric Technology

Visualizing Wearable Medical Device Research Trends: A Co-occurrence Network-Based Bibliometric Analysis

Background. One of the most crucial aspects of someone’s life is health. Therefore, individuals should be conscious about keeping themselves healthy by regular monitoring their health, which can be done with the help of modern medical technologies. Wearable medical devices using wearable sensors are the popular names of emerging technologies in the modern healthcare domain.
 Aim. This work presents the results of a systematic investigation of extensive research that has occurred for the last two decades in these research streams to provide a comprehensive mapping and temporal distribution of wireless medical device research.
 Methods. This study presents a relationship between the bibliographic items, their quality, and the quantity representing the most effective research topics on wearable medical devices. The analysis is performed using two useful parameters, namely a bibliometric network and a co-occurrence matrix. Data collection, data standardization, data mapping, and result analysis are the steps involved in the bibliometric analysis technique. In this study, VOSviewer software for bibliometric analysis is applied to the Scopus database.
 Results. By analysing bibliometric indicators from the Scopus database and using VOSviewer, we represent their distribution in countries, institutions, top researchers, and top journals. Furthermore, we analyse the co-citation of cited authors and the co-occurrence of keywords. The outcomes of the clustering and keyword analysis indicate that the research domain primarily focuses on the Internet of Things, machine learning, wearable sensors, mobile health, electrocardiogram, etc.
 Conclusions. Statistical investigation in association with the visual exploration presented in this article provides more substantial information than either of them used separately. In the future, this article can illuminate researchers and practitioners to develop a different theory to look at the factors that influence predictability in the research domain of wearable medical devices.

Design of a Biaxially Stretchable Microstrip Antenna Enabled by Buckled Au Thin Film on an Elastomeric Substrate

Wearable wireless biomedical electronics enable monitoring and wireless transmission of patient physiological and pathological signals to provide remote guidance for appropriate diagnosis and treatment. As a core component, the antenna must be flexible and stretchable to adapt to the complex mechanical deformations (e.g., stretching, bending, and twisting) induced by human motions. This work proposes a biaxially stretchable microstrip antenna based on buckled gold thin films bonded on an elastomeric substrate. A simplified analytic model validated by simulations and experiments is established to investigate the biaxial buckling behaviors of the thin films within 10% tensile strains. The properties, including resonance frequency, bandwidth, and radiation pattern of the fabricated biaxially stretchable microstrip antenna under various stretched states, are studied by combining experiments and finite element analysis. The effects of biaxial tensile deformations on the resonance frequency, bandwidth, and radiation properties are discussed. Results show that the designed microstrip antenna has a relatively stable performance under both natural and deformed states within 10% of uniaxial and biaxial tensile strains, which enables the designed antenna to have broad application prospects in wearable wireless medical devices for stable transmission of signals between body-worn sensors and terminals, especially for situations accompanied with complex deformations.

Energy-Efficient Compressed Sensing in Cognitive Radio Network for Telemedicine Services

Wireless body area networks (WBAN) are becoming a promising solution for health care applications. WBAN allows monitoring of patients continuously in their own comfort zone. These devices use the industrial, scientific, and medical band (ISM) for communication. This band is overcrowded due to the increasing number of wireless medical devices and other wireless devices occupying this band. This causes interference, which can be damaging and could result in a change in received power. However, WBAN also needs minimum and reliable energy communication for a longer lifetime and improved quality of service. This work addresses both problems and proposes solutions for the same. A cognitive radio controller is employed as a centralized controller with dynamic spectrum allocation properties to mitigate the interference. The sensing of the spectrum is based on compressed sensing with a nonreconstruction model to save energy. To quantify interference measurement, the interference mitigation factor is introduced. Further, to increase energy efficiency, the K-means algorithm is used to cluster WBANs. However, critical emergency data and normal data are categorized as priority data and normal data, respectively, by the proposed priority scheduling algorithm. The performance of this cognitive radio-based system for telemedicine applications is analyzed through simulations. The simulations are performed using MATLAB 2019.

Improved Wireless Medical Cyber-Physical System (IWMCPS) Based on Machine Learning.

Medical cyber-physical systems (MCPS) represent a platform through which patient health data are acquired by emergent Internet of Things (IoT) sensors, preprocessed locally, and managed through improved machine intelligence algorithms. Wireless medical cyber-physical systems are extensively adopted in the daily practices of medicine, where vast amounts of data are sampled using wireless medical devices and sensors and passed to decision support systems (DSSs). With the development of physical systems incorporating cyber frameworks, cyber threats have far more acute effects, as they are reproduced in the physical environment. Patients' personal information must be shielded against intrusions to preserve their privacy and confidentiality. Therefore, every bit of information stored in the database needs to be kept safe from intrusion attempts. The IWMCPS proposed in this work takes into account all relevant security concerns. This paper summarizes three years of fieldwork by presenting an IWMCPS framework consisting of several components and subsystems. The IWMCPS architecture is developed, as evidenced by a scenario including applications in the medical sector. Cyber-physical systems are essential to the healthcare sector, and life-critical and context-aware health data are vulnerable to information theft and cyber-okayattacks. Reliability, confidence, security, and transparency are some of the issues that must be addressed in the growing field of MCPS research. To overcome the abovementioned problems, we present an improved wireless medical cyber-physical system (IWMCPS) based on machine learning techniques. The heterogeneity of devices included in these systems (such as mobile devices and body sensor nodes) makes them prone to many attacks. This necessitates effective security solutions for these environments based on deep neural networks for attack detection and classification. The three core elements in the proposed IWMCPS are the communication and monitoring core, the computational and safety core, and the real-time planning and administration of resources. In this study, we evaluated our design with actual patient data against various security attacks, including data modification, denial of service (DoS), and data injection. The IWMCPS method is based on a patient-centric architecture that preserves the end-user's smartphone device to control data exchange accessibility. The patient health data used in WMCPSs must be well protected and secure in order to overcome cyber-physical threats. Our experimental findings showed that our model attained a high detection accuracy of 92% and a lower computational time of 13 sec with fewer error analyses.

Efficient Certificateless Authenticated Key Agreement for Blockchain-Enabled Internet of Medical Things

Internet of Medical Things (IoMT) plays an essential role in collecting and managing personal medical data. In recent years, blockchain technology has put power in traditional IoMT systems for data sharing between different medical institutions and improved the utilization of medical data. However, some problems in the information transfer process between wireless medical devices and mobile medical apps, such as information leakage and privacy disclosure. This paper first designs a cross-device key agreement model for blockchain-enabled IoMT. This model can establish a key agreement mechanism for secure medical data sharing. Meanwhile, a certificateless authenticated key agreement (KA) protocol has been proposed to strengthen the information transfer security in the cross-device key agreement model. The proposed KA protocol only requires one exchange of messages between the two parties, which can improve the protocol execution efficiency. Then, any unauthorized tampering of the transmitted signed message sent by the sender can be detected by the receiver, so this can guarantee the success of the establishment of a session key between the strange entities. The blockchain ledger can ensure that the medical data cannot be tampered with, and the certificateless mechanism can weaken the key escrow problem. Moreover, the security proof and performance analysis are given, which show that the proposed model and KA protocol are more secure and efficient than other schemes in similar literature.

Electrically Small Antenna For RFID-Based Implantable Medical Sensor

We present a sub-GHz, low profile Electrically Small Antenna (ESA), designed for UHF RFID miniaturised battery free Implantable Wireless Medical Devices (IWMDs). The custom ESA is a linearly polarised dipole, and its topology leverages a meanderline structure to miniaturise its form factor. Furthermore, the ESA utilises a receded ground plane to improve its gain performance and achieve resonance, at the desired sub-GHz design frequency of 915 MHz. The ESA’s dipole characteristics provide an added benefit of 180∘ bi-directional RF signal propagation. The ESA’s design was optimised to integrate the footprint of a UHF RFID sensor chip (SL900A). By integrating the UHF RFID chip on the ESA, a complete wireless battery free sensory medical device, with an integrated antenna, can be realised. The antenna has a formfactor of 12.75×12.25×0.29 mm3. A prototype of the proposed ESA was fabricated and encapsulated in Polydimethylsiloxane (PDMS). Measurements of the prototyped ESA’s input reflection coefficient (S11) and farfield gain values, at 915 MHz, were -26.44 dB and -18.88 dBi, respectively and demonstrated significantly better gain and efficiency performance, when compared to peer reviewed work. The ESA can be used as an antenna for various battery-free subcutaneous implants with a connected sensor (e.g. temperature) or sactuator (e.g. neurostimulator).

Compact Wideband Implanted Antenna for Medical Device Radiocommunications Service, Long Term Evolution, Global System for Mobile Communications, and Wireless Medical Telemetry Service Band Biosensing Applications

Compact Wideband Implanted Antenna for Medical Device Radiocommunications Service, Long Term Evolution, Global System for Mobile Communications, and Wireless Medical Telemetry Service Band Biosensing Applications

Design of Broadband Implantable Antenna for Biomedical Application

<p>A broadband implantable antenna is presented for the biomedical implantable system applications. The proposed antenna adopts a spiral monopole structure to realize the purpose of miniaturization size. The total size of the antenna including the biocompatible superstrates is 15 × 15 × 1.42 mm3 operating frequency at 402 MHz. The effects of some design parameters on performance of proposed antenna are discussed. The simulated and measured in skin-mimicking gel show that the broad bandwidths of 150 MHz (310–460 MHz) and 260 MHz (280–540 MHz) at return loss of 10 dB can be achieved covering the entire Medical Device Radiocommunications Service (MedRadio) and Industrial Scientific Medical (ISM, 433–438 MHz) bands, respectively. The broadband implantable antenna performs an omnidirectional pattern, showing a good candidate for biomedical implantable systems application.</p> <p> </p>

Compact triple-band implantable antenna for multitasking medical devices

Abstract This paper presents a compact implantable antenna’s design, fabrication, and measurement for biotelemetry applications. The proposed design with the size of 255 mm3 provides a triple-band operation that covers all the Medical Implant Communication Service (MICS: 402 MHz), Medical Device Radiocommunications Service (MedRadio: 405 MHz), and Industrial, Scientific, and Medical (ISM: 433, 915 and 2450 MHz) bands simultaneously. The compact structure with triple- band performance is essentially achieved by using a spiral-like radiator loaded with meandered and internal gear-shaped elements excited by a vertical coaxial probe feed. Also, the slots-loaded partial ground plane is utilized to improve impedance matching at the desired frequency bands. The design and analysis of the antenna were carried out using the Ansoft HFSS software in a homogenous skin model and the CST Microwave Studio in a realistic human model. The proposed antenna was fabricated to validate the simulated results, and characteristics of its return loss and radiation patterns were measured in minced pork meat. Moreover, realized gains and specific absorption rate (SAR) values of the antenna were numerically computed using the simulators. Based on the simulated and measured results, the proposed antenna performance was found to be comparable to the limited number of multiband implantable antenna designs reported in the recent literature.

Commercial Off-the-Shelf Components (COTS) in Realizing Miniature Implantable Wireless Medical Devices: A Review.

Over the past decade, there has been exponential growth in the per capita rate of medical patients around the world, and this is significantly straining the resources of healthcare institutes. Therefore, the reliance on smart commercial off-the-shelf (COTS) implantable wireless medical devices (IWMDs) is increasing among healthcare institutions to provide routine medical services, such as monitoring patients’ physiological signals and the remote delivery of therapeutic drugs. These smart COTS IWMDs reduce the necessity of recurring visits of patients to healthcare institutions and also mitigate physical contact, which can minimize the possibility of any potential spread of contagious diseases. Furthermore, the devices provide patients with the benefit of recuperating in familiar surroundings. As such, low-cost, ubiquitous COTS IWMDs have engendered the proliferation of telemedicine in healthcare to provide routine medical services. In this paper, a review work on COTS IWMDs is presented at a macro level to discuss the history of IWMDs, different networked COTS IWMDs, health and safety regulations of COTS IWMDs and the importance of organized procurement. Furthermore, we discuss the basic building blocks of IWMDs and how COTS components can contribute to build these blocks over widely researched custom-built application-specific integrated circuits.

Compact multi-band implantable antenna designs for versatile in-body applications

In this paper, a quad-band implantable antenna (QBIA) and its triple-band miniaturized configuration are presented. The primary radiator of the proposed QBIA consists of four different types of concentric resonators excited by a microstrip feed line. The QBIA design has dimensions of 15 × 15 × 1.27 mm3, and it covers the Medical Device Radiocommunications Service (MedRadio), Medical Implant Communication Service (MICS), Medical Telemetry Service (WMTS), and Industrial, Scientific, and Medical (ISM) bands. The proposed antenna was fabricated to validate the numerical design, and the characteristics of its return loss and radiation patterns were measured in minced meat from pork. The miniaturized version of the QBIA has an ultra-compact size of 4.16 mm3 (4 × 4 × 0.26 mm3), and it offers a triple-band operation covering the ISM and WMTS bands. The proposed triple-band implantable antenna (TBIA) was achieved by using a thinner substrate and optimizing all design parameters of the QBIA. To the best of our knowledge, the suggested QBIA with the novel configuration is the first implantable antenna that simultaneously covers almost all frequency bands allocated for biotelemetry applications. Also, the proposed TBIA is the most miniature triple-band implantable antenna presented in the recent literature, considering the application frequencies.

Data Transmission Enhancement Using Optimal Coding Technique Over In Vivo Channel for Interbody Communication.

Wireless in vivo actuators and sensors are examples of sophisticated technologies. Another breakthrough is the use of in vivo wireless medical devices, which provide scalable and cost-effective solutions for wearable device integration. In vivo wireless body area networks devices reduce surgery invasiveness and provide continuous health monitoring. Also, patient data may be collected over a long period of time. Given the large fading in in vivo channels due to the signal path going through flesh, bones, skins, and blood, channel coding is considered a solution for increasing the efficiency and overcoming inter-symbol interference in wireless communications. Simulations are performed by using 50 MHz bandwidth at Ultra-Wideband frequencies (3.10-10.60 GHz). Optimal channel coding (Turbo codes, Convolutional codes, with the help of polar codes) improves data transmission performance over the in vivo channel in this research. Moreover, the results reveal that turbo codes outperform polar and convolutional codes in terms of bit error rate. Other approaches perform similarly when the information block length is increased. The simulation in this work indicates that the in vivo channel shows less performance than the Rayleigh channel due to the dense structure of the human body (flesh, skins, blood, bones, muscles, and fat).

A Novel Wideband and Multi-band Implantable Antenna Design for Biomedical Telemetry

In this work, a novel multi-tracks wideband and multi-band miniaturized antenna design for implanted medical devices biomedical telemetry is proposed. This antenna entirely covers seven frequency bands which are the bands (401−406) MHz of the Medical Device Radiocommunications Service (MedRadio), the three bands (433.1−434.8), (868.0−868.6), and (902.8−928.0) MHz of the Industrial, Scientific, and Medical (ISM), and the three bands (608−614) MHz, and (1.395−1.400) and (1.427−1.432) GHz of the Wireless Medical Telemetry Service (WMTS). The antenna possesses a compact full size of (19.5 × 12.9 × 0.456) mm3. The antenna miniaturization and impedance bandwidth enhancement are achieved using two techniques: the patch slotting and insertion of open-end slots in the ground plane, respectively. Prototype of proposed antenna with multi-tracks has been fabricated and tested in free space. The comparison between the simulated and measured reflection coefficient has been done and found in good agreement with each other. Furthermore, simulations of the proposed antenna implanted in the underneath the scalp in a realistic human model shows a wideband operation from 0.19 to 0.94 GHz, and from 1.38 to 1.54 GHz corresponding to return loss (S11 ≤ −10 dB). Link budget calculation is performed to specify the range of telemetry considering both Specific Absorption Rate (SAR) restrictions and effective isotropic radiated power (EIRP) limitations. The designed implantable antenna with full ground plane presents an appropriate reflection coefficient for muscle implantation. Furthermore, the designed implanted muscle antenna may be also suitable for skin implantation.

A Novel Dual-Band Implantable Antenna for Pancreas Telemetry Sensor Applications

In this study, a novel implantable dual-band planar inverted F-antenna (PIFA) is proposed and designed for wireless biotelemetry. The developed antenna is intended to operate on the surface of the pancreas within the Medical Device Radiocommunications Service (MedRadio 401–406 MHz) and the industrial scientific and medical band (ISM, 2.4–2.5 GHz). The design analysis was carried out in two steps, initially inside a canonical model representing the pancreas, based on a finite element method (FEM) numerical solver. The proposed antenna was further simulated inside the human body taking into account the corresponding dimensions of the tissues and the electrical properties at the frequencies of interest using a finite-difference time-domain (FDTD) numerical solver. Resonance, radiation performance, electrical field attenuation, total radiated power, and specific absorption rate (SAR), which determines the safety of the patient and the maximum permissible input power and other electromagnetic parameters, are presented and evaluated.

Securing Fuzzy Vault Enabled Authentication in Body Area Networks-Based Smart Healthcare

The emergence of body area networks (BANs) has paved the way for real-time sensing of human biometrics in addition to remote control of smart wireless medical devices, which in turn are beginning to revolutionize the smart healthcare industry. However, due to their limited power and computational capabilities, they are vulnerable to a myriad of security attacks. To secure BAN sensors against these threats processor-intensive cryptographic techniques need to be avoided as they are not suitable in this context. This article focuses on authentication service for BAN sensors and proposes an original scheme named “RAFV: Rotational Assisted Fuzzy Vaults” to harden the security of any authentication solution using the fuzzy vault construction approach. The evaluation results have shown that RAFV can successfully conceal the secret of the vault even if the locking elements are known to the adversary. Also, RAFV may improve upon communication overhead by enabling a reduction in the size of the vault without compromising its security. It has achieved all of this while remaining competitive with regards to additional computational overhead.

Wide Band Meandered-Loop Ground Radiation Antenna for Biomedical Applications

The concept of wireless implantable medical devices (IMDs) is becoming more popular as the world’s population ages and concerns about public health grow. Implantable antennas have figured prominently in wireless communication among IMDs and external infrastructures, yet they have subsequently become a major study area. Among the most difficult aspects of building implantable antennas is to varied physical tissues and fluids act as dielectric stress on antenna, affecting its efficiency dramatically. Ground radiation antenna was particularly designed for the antenna size reduction. The features of the ground have an impact on it. There is variance in the radiation field with similar frequency and antenna length yet varied ground conductance. It has been discovered that when the ground conductance is low, the radiation field is minimal and the orientation of the radiation field modifies. A meandered-loop ground radiation antenna (MGRA) was designed by coupling the meandered-loop structure to the ground radiating plane using only one electrical element. The proposed antenna was studied for biomedical applications at ISM band in the range between 2.4 to 2.8 GHz. The overall size of antenna is 30×24 mm2 making it suitable for the implantable applications. The bandwidth of the MGRA was further improved by using stub structures. The single layer skin model simulation showed that |S11| parameter as −21.21 dB at the resounding frequency of 2.40 GHz. Major factors like impedance match gain, radiation effectiveness and Specific Absorption Rate (SAR) had also been evaluated in this study.