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The magnetic relaxation of magnetic nanoparticles (MNPs) has been used as a potential heating agent for magnetic hyperthermia treatment (MHT). This requires an understanding of the heating mechanism of MNPs, such as Néel relaxation; however, few studies about magnetic relaxation using a low-frequency AC magnetic field have been reported. This study attempts to clarify the correlation between the dominance of Néel relaxation in low-frequency AC fields and the magnetic properties. Nanoparticles of Ni 0.8 Zn 0.2 Fe 2 O 4 coated with poly(ethylene glycol) (PEG) were synthesized in various sizes ( d  = 12, 15, and 19 nm), and were subjected to structural analysis, PEG modification, and magnetic measurements. The PEG400 coating results in a hydrodynamic diameter ten times smaller than that of our previous sample. The heat generation experiment was conducted on samples suspended in solvents of different viscosities in the presence of an AC field ( h  = 3.2 kAm −1 , f  = 90 kHz). The specific absorption rate (SAR) as a function of the viscosity of the 15-nm NP sample is consistent with the theoretically calculated value in cases where the Néel relaxation is dominant. Therefore, we conclude that the Néel relaxation dominates the heating mechanism of the 15 nm sample. Rather than being fully superparamagnetic, this sample was partly superparamagnetic and slightly ferromagnetic, with the dominance of the Néel relaxation to a certain degree affected by spin blocking. Detailed analysis of the magnetic relaxation is crucial to improve the heating efficiency of MNPs for MHT.

Compact low specific absorption rate (SAR) hexa-band planar inverted-F antenna (PIFA) with independent resonant frequency control is presented in this study. Two trapezoidal shaped slots are etched on the coplanar waveguide (CPW)-fed PIFA-radiating plate to create two independent resonant frequencies as well as the fundamental CPW-fed PIFA itself. Three coupled slots are added within the ground plane to create additional three independent resonant frequencies with slight effect on the other resonant frequencies. Multiband (dual, tri, quad, penta and hexa) band capabilities with bandwidth enhancement and acceptable SAR values are realised for different wireless communication applications. The SAR of human head is investigated by using Computer Simulation Technology (CST) 2012 Microwave Studio Hugo Voxel Model. The proposed antennas are fabricated and there is a good agreement between measured and simulated results.

The activation of magnetic nanoparticles in hyperthermia treatment by an external alternating magnetic field is a promising technique for targeted cancer therapy. The external alternating magnetic field generates heat in the tumor area, which is utilized to kill cancerous cells. Depending on the tumor type and site to be targeted, various types of magnetic nanoparticles, with variable coating materials of different shape and surface charge, have been developed. The tunable physical and chemical properties of magnetic nanoparticles enhance their heating efficiency. Moreover, heating efficiency is directly related with the product values of the applied magnetic field and frequency. Protein corona formation is another important parameter affecting the heating efficiency of MNPs in magnetic hyperthermia. This review provides the basics of magnetic hyperthermia, mechanisms of heat losses, thermal doses for hyperthermia therapy, and strategies to improve heating efficiency. The purpose of this review is to build a bridge between the synthesis/coating of magnetic nanoparticles and their practical application in magnetic hyperthermia.

Implantable antennas are mandatory to transfer data from implants to the external world wirelessly. Smart implants can be used to monitor and diagnose the medical conditions of the patient. The dispersion of the dielectric constant of the tissues and variability of organ structures of the human body absorb most of the antenna radiation. Consequently, implanting an antenna inside the human body is a very challenging task. The design of the antenna is required to fulfill several conditions, such as miniaturization of the antenna dimension, biocompatibility, the satisfaction of the Specific Absorption Rate (SAR), and efficient radiation characteristics. The asymmetric hostile human body environment makes implant antenna technology even more challenging. This paper aims to summarize the recent implantable antenna technologies for medical applications and highlight the major research challenges. Also, it highlights the required technology and the frequency band, and the factors that can affect the radio frequency propagation through human body tissue. It includes a demonstration of a parametric literature investigation of the implantable antennas developed. Furthermore, fabrication and implantation methods of the antenna inside the human body are summarized elaborately. This extensive summary of the medical implantable antenna technology will help in understanding the prospects and challenges of this technology.

The ever-increasing demand and need for high-speed communication have generated intensive research in the field of fifth-generation (5G) technology. Sub-6 GHz 5G mid-band spectrum is the focus of the researchers due to its meritorious ease of deployment in the current scenario with the already existing infrastructure of the 4G-LTE system. The 5G technology finds applications in enormous fields that require high data rates, low latency, and stable radiation patterns. One of the major sectors that benefit from the outbreak of 5G is the field of flexible electronics. Devices that are compact need an antenna to be flexible, lightweight, conformal, and still have excellent performance characteristics. Flexible antennas used in wireless body area networks (WBANs) need to be highly conformal to be bent according to the different curvatures of the human body at different body parts. The specific absorption rate (SAR) must be at a permissible level for such an antenna to be suited for WBAN applications. This paper gives a comprehensive review of the current state of the art flexible antennas in a sub-6 GHz 5G band. Furthermore, this paper gives a key insight into the materials for a flexible antenna, the parameters considered for the design of a flexible antenna for 5G, the challenges for the design, and the implementation of a flexible antenna for 5G.

In recent years, there has been a surge of interest in the field of wireless communication for designing a monitoring system to observe the activity of the human body remotely. With the use of wireless body area networks (WBAN), chronic health and physical activity may be tracked without interfering with routine lifestyle. This crucial real-time data transmission requires low power, high speed, and broader bandwidth communication. Ultrawideband (UWB) technology has been explored for short-range and high-speed applications to cater to these demands over the last decades. The antenna is a crucial component of the WBAN system, which lowers the overall system’s performance. The human body’s morphology necessitates a flexible antenna. In this article, we comprehensively survey the relevant flexible materials and their qualities utilized to develop the flexible antenna. Further, we retrospectively investigate the design issues and the strategies employed in designing the flexible UWB antenna, such as incorporating the modified ground layer, including the parasitic elements, coplanar waveguide, metamaterial loading, etc. To improve isolation and channel capacity in WBAN applications, the most recent decoupling structures proven in UWB MIMO technology are presented.

The field of flexible antennas is witnessing an exponential growth due to the demand for wearable devices, Internet of Things (IoT) framework, point of care devices, personalized medicine platform, 5G technology, wireless sensor networks, and communication devices with a smaller form factor to name a few. The choice of non-rigid antennas is application specific and depends on the type of substrate, materials used, processing techniques, antenna performance, and the surrounding environment. There are numerous design innovations, new materials and material properties, intriguing fabrication methods, and niche applications. This review article focuses on the need for flexible antennas, materials, and processes used for fabricating the antennas, various material properties influencing antenna performance, and specific biomedical applications accompanied by the design considerations. After a comprehensive treatment of the above-mentioned topics, the article will focus on inherent challenges and future prospects of flexible antennas. Finally, an insight into the application of flexible antenna on future wireless solutions is discussed.

[...] significant challenges have to be overcome before using 7T TOF in clinical applications: I RF induced specific absorption rate (SAR) substantially increases at UHF, preventing the use of standard RF pulses (venous Saturation (SAT), Magnetization Transfer (MT)) to improve TOF contrast. Estimation of the spatial receive profile variations removed from both datasets for better visibility of smaller vessels. [figure omitted; refer to PDF] Conclusions We demonstrate, with appropriate RF pulse design, substantial gains in contrast and B1+ homogeneity for TOF angiography at 7T.

Access to MRI is limited for patients with deep brain stimulation (DBS) implants due to safety hazards, including radiofrequency (RF) heating of tissue surrounding the leads. Computational models provide an exquisite tool to explore the multi-variate problem of RF heating and help better understand the interaction of electromagnetic fields and biological tissues. This paper presents a computational approach to assess RF-induced heating, in terms of specific absorption rate (SAR) in the tissue, around the tip of bilateral DBS leads during MRI at 64MHz/1.5 T and 127 MHz/3T. Patient-specific realistic lead models were constructed from post-operative CT images of nine patients operated for sub-thalamic nucleus DBS. Finite element method was applied to calculate the SAR at the tip of left and right DBS contact electrodes. Both transmit head coils and transmit body coils were analyzed. We found a substantial difference between the SAR and temperature rise at the tip of right and left DBS leads, with the lead contralateral to the implanted pulse generator (IPG) exhibiting up to 7 times higher SAR in simulations, and up to 10 times higher temperature rise during measurements. The orientation of incident electric field with respect to lead trajectories was explored and a metric to predict local SAR amplification was introduced. Modification of the lead trajectory was shown to substantially reduce the heating in phantom experiments using both conductive wires and commercially available DBS leads. Finally, the surgical feasibility of implementing the modified trajectories was demonstrated in a patient operated for bilateral DBS. •Access to MRI is limited for patients with DBS implants due to safety hazards, including radiofrequency heating of tissue surrounding the leads.•Computational models provide an exquisite tool to explore the multi-variate problem of RF implant heating.•We used a computational approach to assess RF heating around tips of bilateral DBS leads during MRI at 1.5T and 3T using realistic DBS lead models.•A substantial difference was found between the SAR and temperature rise at the tip of right and left DBS leads.•Modification of DBS lead trajectory reduced heating in phantom experiments using both conductive wires and commercially available DBS leads.

This paper presents the development of a new complete wearable system for detecting breast tumors based on fully textile antenna-based sensors. The proposed sensor is compact and fully made of textiles so that it fits conformably and comfortably on the breasts with dimensions of 24 × 45 × 0.17 mm3 on a cotton substrate. The proposed antenna sensor is fed with a coplanar waveguide feed for easy integration with other systems. It realizes impedance bandwidth from 1.6 GHz up to 10 GHz at |S11| ≤ −6 dB (VSWR ≤ 3) and from 1.8 to 2.4 GHz and from 4 up to 10 GHz at |S11| ≤ −10 dB (VSWR ≤ 2). The proposed sensor acquires a low specific absorption rate (SAR) of 0.55 W/kg and 0.25 W/kg at 1g and 10 g, respectively, at 25 dBm power level over the operating band. Furthermore, the proposed system utilizes machine-learning algorithms (MLA) to differentiate between malignant tumor and benign breast tissues. Simulation examples have been recorded to verify and validate machine-learning algorithms in detecting tumors at different sizes of 10 mm and 20 mm, respectively. The classification accuracy reached 100% on the tested dataset when considering |S21| parameter features. The proposed system is vision as a “Smart Bra” that is capable of providing an easy interface for women who require continuous breast monitoring in the comfort of their homes.