Design of hearing aid shells by three dimensional laser scanning and mesh reconstruction

Hearing aid shells (or earmolds) must couple the hearing aid with the user's ear. Earmolds have to fit the subject's outer ear canal properly to ensure a good performance of the aid. Because of the great variability in the anatomical pattern of the ear, earmolds are custom made. At present, an impression of the subject's ear canal is taken and used to fabricate the silicon-made mold. The postimpression activities that typically are performed during the fabrication process modify the physical dimensions of the resulting earmold and thus affect the fit of the product. A novel system for 3-D laser scanning and mesh reconstruction of the surface of ear canal impressions is presented. The reconstructed impression can be digitally stored and passed directly to dedicated CAD 3-D printing machines to model the silicon earmold and thus achieve the best possible fit. The proposed system is based on a couple of cameras and a commercial laser for the surface digitization and on a straightforward algorithm, based on the deformation of a geometric model, for the reconstruction of the acquired surface. Measurements on objects of well-known geometric features and dimensions are performed to assess the accuracy and repeatability levels of this 3-D acquisition system. Robustness to noise of the proposed reconstruction algorithm is determined by simulations with a synthetic test surface. Finally, the first measurements (acquisition+reconstruction) of closed surfaces from ear canal impressions are reported

Assessment of foetal exposure to the homogeneous magnetic field harmonic spectrum generated by electricity transmission and distribution networks

During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level

Use of Nanoparticles as Nanoelectrodes in Contact-Less Cell Membrane Permeabilization by Time-Varying Magnetic Field: A Computational Study

This paper describes a computational approach for the assessment of electric field enhancement by using highly conductive gold nanoparticles (Au NPs) in time-varying electromagnetic fields cell membrane permeabilization, estimating the influence of the presence of Au NPs on transmembrane potential and on the pore opening dynamics. To account for variability and uncertainty about geometries and relative placement and aggregations of the Au NPs, three different NP configurations were considered: spherical Au NPs equally spaced around the cell; cubic Au NPs, for accounting for the possible edge effect, equally spaced around the cell; and spherical Au NPs grouped in clusters. The results show that the combined use of Au NPs and a time-varying magnetic field can significantly improve the permeabilization of cell membranes. The variability of NPs' geometries and configurations in proximity of the cell membrane showed to have a strong influence on the pore opening mechanism. The study offers a better comprehension of the mechanisms, still not completely understood, underlying cell membrane permeabilization by time-varying magnetic fields

Effect of the Interindividual Variability on Computational Modeling of Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers low intensity, direct current to cortical areas facilitating or inhibiting spontaneous neuronal activity. This paper investigates how normal variations in anatomy may affect the current flow through the brain. This was done by applying electromagnetic computational methods to human models of different age and gender and by comparing the electric field and current density amplitude distributions within the tissues. Results of this study showed that the general trend of the spatial distributions of the field amplitude shares some gross characteristics among the different human models for the same electrode montages. However, the physical dimension of the subject and his/her morphological and anatomical characteristics somehow influence the detailed field distributions such as the field values

A new handheld electromagnetic cortical stimulator for brain mapping during open skull neurosurgery: a feasibility study

Transcranial magnetic stimulations have provided invaluable tools for investigating nervous system functions in a preoperative context; in this paper we propose an innovative tool to extend the magnetic stimulation to an open skull context as a promising approach to map the brain cortex. The present gold standard for intraoperative functional mapping of the brain cortex, the direct brain stimulation, has a low spatial resolution and limited penetration and focusing capabilities. The magnetic stimulatory device that we present, is designed to overcome these limitations, while working with low currents and voltages. In the present work we propose an early study of feasibility, in which the possibility of exploiting a train of fast changing magnetic fields to reach the neuron's current thresholds is investigated. Measurements of electric field intensity at different distances from the coil, showed that the magnetic stimulator realized is capable of delivering an electric field on a loop of wire theoretically sufficient to evoke neuron's action potential, thus showing the approach' feasibility

COVID-19 and Pregnancy: An Updated Review about Evidence-Based Therapeutic Strategies

The COVID-19 pandemic posed a significant challenge for clinicians in managing pregnant women, who were at high risk of virus transmission and severe illness. While the WHO declared in May 2023 that COVID-19 is no longer a public health emergency, it emphasized that it remains a global health threat. Despite the success of vaccines, the possibility of new pandemic waves due to viral mutations should be considered. Ongoing assessment of the safety and effectiveness of pharmacological therapies is crucial in clinical practice. This narrative review summarizes the evidence-based therapeutic strategies for pregnant women with COVID-19, considering over three years of pandemic experience. The review discusses the safety and effectiveness of various drug regimens (antivirals, anticoagulants, corticosteroids, immunoglobulins, monoclonal antibodies, and therapeutic gases) and procedures (prone positioning and extracorporeal membrane oxygenation). Drugs with contraindications, inefficacy during pregnancy, or unknown adverse effects were excluded from our evaluation. The aim is to provide healthcare professionals with a comprehensive guide for managing pregnant women with COVID-19 based on lessons learned from the pandemic outbreak

Assessing Reliability and Agreement of Repeated Measurements by Hierarchical Modeling

We present the use of linear hierarchical models to assess the repeatability and agreement of two or more measurement devices. The idea is illustrated by means of two sets of data. The first considers eight different protocols for the recording of distortion product otoacoustic emissions in Sprague-Dawley rats. The second data set was obtained from the calibration of two types of extremely low frequency magnetic field dosimeters

Exposure Assessment for Wearable Patch Antenna Array at Millimeter Waves

International audienceThe upcoming deployment of wireless networks and systems operating in the upper part of the microwave spectrum, including millimeter-wave (mmWave) frequencies, motivates user exposure assessment studies at these emerging frequencies. At mmWaves, the power absorption is mainly limited to cutaneous and subcutaneous tissues. Till now, there is no literature consensus on the skin model to employ in computational exposure assessment studies. For these reasons, this work analyses four different models of the most superficial tissues with different degree of details exposed to wearable patch antennas operating at 28 GHz and 39 GHz. The results for the layered models are compared to the homogeneous one. Simulations were performed using the FDTD method, implemented in the Sim4life platform and the exposure was assessed in terms of the absorbed power density averaged over 1 cm2 and 4 cm2 (Sab). The data showed that the homogeneous model underestimates the peak value of Sab obtained for multi-layer models in the stratum corneum (by 8% to 12% depending on the number of layers of the model and the frequency) when the simulated models have the same reflection coefficient. Conversely, there are no substantial differences in the exposure levels between the layered models