Journal: Bioelectromagnetics

Abbreviation

Bioelectromagnetics

Publisher

Wiley

Journal Volumes

ISSN

0197-8462
1521-186X

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Publications 1 - 10 of 23
  • Differences in RF energy absorption in the heads of adults and children
    Item type: Conference Paper
    Christ, Andreas; Kuster, Niels (2005)
    Bioelectromagnetics
  • Short-Dipole Sensor Response Linearization Through Physics-Informed Neural Networks
    Item type: Journal Article
    Fasse, Alessandro; Meyer, Romain; Neufeld, Esra; et al. (2025)
    Bioelectromagnetics
    Short-dipole diode sensors loaded with highly resistive lines are commonly used to measure the time-averaged square of the high-frequency electromagnetic field amplitude directly. Their precision, simplicity, broadband, high dynamic range capability, and minimal scattering make them ideal for application in the near-field of sources, particularly for demonstrating compliance with exposure limits. However, the usage of these sensors to cover multiple orders of magnitude of field amplitude requires signal-specific linearization of the sensor response. Traditionally, linearization had been performed for each signal or modulation by measurement and, more recently, by simulations based on a calibrated sensor model. These approaches have become prohibitively expensive with the launch of the fifth generation of mobile communication (5G), which added thousands of diverse and complex modulation schemes. In response to these challenges, we first developed an innovative approach to accelerate sensor model simulations with an enhancement of accuracy, which allows us to subsequently establish a data set comprising a large number of probe parameters and signal characteristic configurations. Subsequently, a physics-informed neural network (PINN) was trained with readily accessible signal characteristics to obtain on-the-fly linearization parameters with acceptable uncertainties across the relevant dynamic range. In contrast to traditional artificial intelligence (AI) models that predominantly rely on pattern recognition from precomputed data, our approach ensures that the model captures the intrinsic relationships and system dynamics inherent to the physical phenomena under study. Our AI-based approach achieves an error below 0.4 dB at peak specific absorption rate (SAR) values of up to > 200 W kg$^{-1}$. In addition, AI accelerates the determination of linearization parameters by a factor > 34,000x and reduces storage requirements > 350,000 times, allowing linearization parameters to be computed on site.
  • Dealing with crosstalk in electromagnetic field measurements of portable devices
    Item type: Journal Article
    Eeftens, Marloes; Struchen, Benjamin; Roser, Katharina; et al. (2018)
    Bioelectromagnetics
  • Traceable Assessment of the Absorbed Power Density of Body Mounted Devices at Frequencies Above 10 GHz
    Item type: Journal Article
    Chitnis, Ninad; Karimi, Fariba; Kühn, Sven; et al. (2025)
    Bioelectromagnetics
    In this study, a comprehensive approach for the experimental assessment of the absorbed power density (APD) is developed. The method includes several novel components: (i) a specialized probe, (ii) a composite phantom, (iii) a reconstruction technique, (iv) a calibration method, and (v) a validation process. The described solution has been developed for the frequency range from 24 to 30 GHz, but can be extended to all frequency bands between 10 and 45 GHz. A novel composite phantom emulates the reflection and transmission coefficients of human skin for propagating and evanescent modes, while its increased penetration depth, in comparison to dermis tissue, enables the measurement of the induced electromagnetic fields (EMFs) with a new miniaturized dosimetric broadband probe. The implementation has a wide dynamic range and sufficient spatial resolution to use it for type approval of mobile devices. Its probe is calibrated with low uncertainty in a novel, traceable setup. A set of reference antennas with known numerical target values for the APD has been compiled to validate the measurement system. The validation demonstrates that the deviation is within the expanded uncertainty of 1.6 dB for pAPD and (Formula presented.) 1.5 dB for psAPD.
  • Dosimetric Electromagnetic Safety of People With Implants: A Neglected Population?
    Item type: Journal Article
    Kranold, Lena; Xi, Jingtian; Goren, Tolga; et al. (2025)
    Bioelectromagnetics
    Electromagnetic (EM) safety guidelines are designed to protect the general public and workers from the risks posed by exposure to EM sources of all types, with the exception of medical EM sources. However, it has never been systematically evaluated whether individuals with conductive implants are also protected by these guidelines or whether the local field enhancement due to presence of the implant may pose an unacceptable risk under certain realistic exposure conditions. To address this important knowledge and regulatory gap, we first evaluated the upper bound of the local enhancement of bare and insulated generic implants of 0.5 λ (approximately equal to resonant) and 0.1 λ lengths, but restricted the maximum length to 2 m, as a function of tissue properties and frequency (10 kHz to 1 GHz). Results for uniform electric field excitation showed local enhancement of psSAR10mg and of locally averaged E-field, respectively, compared to the background in the presence of a generic implant of 10 dB (1 GHz) to over 100 dB at frequencies under 100 MHz. In the next step, we tested the hypothesis that fields induced inside the human body by realistic near-field sources are not sufficiently uniform to generate results in enhancement that could pose unacceptable risk. Common implant trajectories were inserted into the Virtual Population human anatomical model Ella V3.0, and the model was exposed to the following conditions (i) a standard source representing a wireless power transfer source operating at 85 kHz and (ii) a dipole source that operates at 450 MHz within the current exposure limits. Results show that the safety limit is exceeded at the tip of the implant by a factor of > 10 (> 20 dB) or > 115 V/m at 85 kHz, whereas the locally induced specific absorption rate averaged over 10 mg at 450 MHz was 7.9 W/kg, resulting in a temperature increase after 6 min of < 0.4 K. Hence, as the hypothesis was falsified at frequencies < 450 MHz, patients with implants are inadequately protected by current safety and product guidelines. In the discussions, proposals for how to close this regulatory gap are provided. Bioelectromagnetics. 00:00–00, 2025. © 2025 Bioelectromagnetics Society.
  • Anatomical Model Uncertainty for RF Safety Evaluation of Metallic Implants Under MRI Exposure
    Item type: Journal Article
    Yao, Aiping; Zastrow, Earl; Cabot, Eugenia; et al. (2019)
    Bioelectromagnetics
  • Reflection Properties of the Human Skin From 40 to 110 GHz: A Confirmation Study
    Item type: Journal Article
    Christ, Andreas; Aeschbacher, Adrian; Rouholahnejad, Fereshteh; et al. (2021)
    Bioelectromagnetics
    Several recent theoretical dosimetric studies above 6 GHz apply generic layered skin models. For this frequency range, new experimental phantoms for over-the-air performance of wireless devices were proposed that simulate the impedance matching effects of the stratum corneum layer (SCL) with a low-loss coating layer. The aim of this study was to verify the skin models by comparing their reflection coefficients S-11 with measurements of 37 human volunteers (21 males, 16 females, 5-80 years) at 21 body locations (10 at palm, 11 at arm/face) with different SCL thicknesses, using waveguides covering frequencies from 40 to 110 GHz. Such measurements were also carried out with the phantom material. The statistical analysis showed strong evidence that S-11 depends on the SCL thickness and no evidence that S-11 depends on sex. The measured S-11 values for thin and thick skin can be represented by SCL layers of 15 and 140 mu m, respectively. These values correspond well to the assumptions of previous studies. (The cohort did not include volunteers doing heavy manual work.) The phantom material mimics the matching effect of the SCL with deviations from the waveguide measurements of less than 0.85 dB (22%), which confirms the suitability of layered phantoms to represent the electromagnetic reflection/absorption of human skin. © 2021 Bioelectromagnetics Society
  • Novel ETV6-RUNX1 Mouse Model to Study the Role of ELF-MF in Childhood B-Acute Lymphoblastic Leukemia: a Pilot Study
    Item type: Journal Article
    Campos-Sanchez, Elena; Vicente-Duenas, Carolina; Rodriguez-Hernandez, Guillermo; et al. (2019)
    Bioelectromagnetics
  • Recommendations for the Safe Application of Temporal Interference Stimulation in the Human Brain Part I: Principles of Electrical Neuromodulation and Adverse Effects
    Item type: Journal Article
    Cassarà, Antonino M.; Newton, Taylor H.; Zhuang, Katie; et al. (2025)
    Bioelectromagnetics
    Temporal interference stimulation (TIS) is a new form of transcranial electrical stimulation (tES) that has been proposed as a method for targeted, non-invasive stimulation of deep brain structures. While TIS holds promise for a variety of clinical and non-clinical applications, little data is yet available regarding its effects in humans and its mechanisms of action. In order to inform the design and safe conduct of experiments involving TIS, researchers require quantitative guidance regarding safe exposure limits and other safety considerations. To this end, we undertook a two-part effort to determine frequency-dependent thresholds for applied currents below which TIS is unlikely to pose risk to humans in terms of heating or unwanted stimulation. Part I of this effort, described here, comprises a summary of the current knowledge pertaining to the safety of TIS and related techniques. Specifically, we provide: i) a broad overview of the electrophysiological impacts neurostimulation, ii) a review of the (bio-)physical principles underlying the mechanisms of action of transcranial alternating/direct stimulation (tACS/tDCS), deep brain stimulation (DBS), and TIS, and iii) a comprehensive survey of the adverse effects (AEs) associated with each technique as reported in the scientific literature and regulatory and clinical databases. In Part II, we perform an in silico study to determine field exposure metrics for tDCS/tACS and DBS under normal (safe) operating conditions and infer frequency-dependent current thresholds for TIS that result in equivalent levels of exposure.
  • Recommendations for the Safe Application of Temporal Interference Stimulation in the Human Brain Part II: Biophysics, Dosimetry, and Safety Recommendations
    Item type: Journal Article
    Cassara, Antonino M.; Newton, Taylor H.; Zhuang, Katie; et al. (2025)
    Bioelectromagnetics
    Temporal interference stimulation (TIS) is a new form of transcranial electrical stimulation (tES) that has been proposed as a method for targeted, noninvasive stimulation of deep brain structures. While TIS holds promise for a variety of clinical and nonclinical applications, little data is yet available regarding its effects in humans and its mechanisms of action. To inform the design and safe conduct of experiments involving TIS, researchers require quantitative guidance regarding safe exposure limits and other safety considerations. To this end, we undertook a two-part effort to determine frequency-dependent thresholds for applied currents below which TIS is unlikely to pose risk to humans in terms of heating or unwanted stimulation. In Part II of this effort, described here, we draw on a previously compiled list (see Part I) of adverse effects (AEs) reported for transcranial direct/alternating current stimulation (tDCS/ACS), deep brain stimulation (DBS), and TIS to determine biophysics-informed exposure metrics for assessing safety. Using an in silico approach, we conduct multiphysics simulations of various tACS, DBS, and TIS exposure scenarios in an anatomically detailed head and brain model. By matching the stimulation in terms of the identified exposure metrics, we infer frequency-dependent TIS parameters that produce exposure conditions equivalent to those known to be safe for tACS and DBS. Based on the results of our simulations and existing knowledge regarding tES and DBS safety, we propose frequency-dependent thresholds below which TIS voltages and currents are unlikely to pose a risk to humans. Safety-related data from ongoing and future human studies are required to verify and refine the thresholds proposed here.
Publications 1 - 10 of 23