Precise SAR Measurements In The Near-Field of RF Antenna Systems

Wireless devices must meet specific safety radiation limits, and in order to assess the health affects of such devices, standard procedures are used in which standard phantoms, tissue-equivalent liquids, and miniature electric field probes are used. The accuracy of such measurements depend on the precision in measuring the dielectric properties of the tissue-equivalent liquids and the associated calibrations of the electric-field probes. This thesis describes work on the theoretical modeling and experimental measurement of the complex permittivity of tissue-equivalent liquids, and associated calibration of miniature electric-field probes. The measurement method is based on measurements of the field attenuation factor and power reflection coefficient of a tissue-equivalent sample. A novel method, to the best of the author's knowledge, for determining the dielectric properties and probe calibration factors is described and validated. The measurement system is validated using saline at different concentrations, and measurements of complex permittivity and calibration factors have been made on tissue-equivalent liquids at 900MHz and 1800MHz. Uncertainty analysis have been conducted to study the measurement system sensitivity. Using the same waveguide to measure tissue-equivalent permittivity and calibrate e-field probes eliminates a source of uncertainty associated with using two different measurement systems. The measurement system is used to test GSM cell-phones at 900MHz and 1800MHz for Specific Absorption Rate (SAR) compliance using a Specific Anthropomorphic Mannequin phantom (SAM)

In-vitro mapping of E-fields induced near pacemaker leads by simulated MR gradient fields

<p>Abstract</p> <p>Background</p> <p>Magnetic resonance imaging (MRI) of patients with implanted cardiac pacemakers is generally contraindicated but some clinicians condone scanning certain patients. We assessed the risk of inducing unintended cardiac stimulation by measuring electric fields (E) induced near lead tips by a simulated MRI gradient system. The objectives of this study are to map magnetically induced E near distal tips of leads in a saline tank to determine the spatial distribution and magnitude of E and compare them with E induced by a pacemaker pulse generator (PG).</p> <p>Methods</p> <p>We mapped magnetically induced E with 0.1 mm resolution as close as 1 mm from lead tips. We used probes with two straight electrodes (e.g. wire diameter of 0.2 mm separated by 0.9 mm). We generated magnetic flux density (B) with a Helmholtz coil throughout 0.6% saline in a 24 cm diameter tank with (dB/dt) of 1 T/sec (1 kHz sinusoidal waveform). Separately, we measured E near the tip of leads when connected to a PG set to a unipolar mode. Measurements were non-invasive (not altering the leads or PG under study).</p> <p>Results</p> <p>When scaled to 30 T/s (a clinically relevant value), magnetically-induced E exceeded the E produced by a PG. The magnetically-induced E only occurred when B was coincident with or within 15 msec of implantable pacemaker's pulse.</p> <p>Conclusions</p> <p>Potentially hazardous situations are possible during an MR scan due to gradient fields. Unintended stimulation can be induced via abandoned leads and leads connected to a pulse generator with loss of hermetic seal at the connector. Also, pacemaker-dependent patients can receive drastically altered pacing pulses.</p

Validation of 24-hour ambulatory gait assessment in Parkinson's disease with simultaneous video observation

<p>Abstract</p> <p>Background</p> <p>Parkinson's disease (PD) is a neurodegenerative disorder resulting in motor disturbances that can impact normal gait. Although PD initially responds well to pharmacological treatment, as the disease progresses efficacy often fluctuates over the course of the day, and clinical management would benefit from long-term objective measures of gait. We have previously described a small device worn on the shank that uses acceleration and angular velocity sensors to calculate stride length and identify freezing of gait in PD patients. In this study we extend validation of the gait monitor to 24-h using simultaneous video observation of PD patients.</p> <p>Methods</p> <p>A sleep laboratory was adapted to perform 24-hr video monitoring of patients while wearing the device. Continuous video monitoring of a sleep lab, hallway, kitchen and conference room was performed using a 4-camera security system and recorded to hard disk. Subjects (3) wore the gait monitor on the left shank (just above the ankle) for a 24-h period beginning around 5 pm in the evening. Accuracy of stride length measures were assessed at the beginning and end of the 24-h epoch. Two independent observers rated the video logs to identify when subjects were walking or lying down.</p> <p>Results</p> <p>The mean error in stride length at the start of recording was 0.05 m (SD 0) and at the conclusion of the 24 h epoch was 0.06 m (SD 0.026). There was full agreement between observer coding of the video logs and the output from the gait monitor software; that is, for every video observation of the subject walking there was a corresponding pulse in the monitor data that indicated gait.</p> <p>Conclusions</p> <p>The accuracy of ambulatory stride length measurement was maintained over the 24-h period, and there was 100% agreement between the autonomous detection of locomotion by the gait monitor and video observation.</p

Eight-Port Modified E-Slot MIMO Antenna Array with Enhanced Isolation for 5G Mobile Phone

An eight-element antenna system operating at sub 6 GHz is presented in this work for a future multiple-input multiple-output (MIMO) system based on a modified E-slot on the ground. The modified E-slot significantly lowers the coupling among the antenna components by suppressing the ground current effect. The design concept is validated by accurately measuring and carefully fabricating an eight-element MIMO antenna. The experimentation yields higher element isolation greater than −21 dB in the 3.5 GHz band and the desired band is achieved at −6 dB impedance bandwidth. The E-shape slot occupies an area of 17.8 mm × 5.6 mm designed on an FR-4 substrate with dimensions of 150 mm × 75 mm × 0.8 mm. We fed the I-antenna element with an L-shape micro-strip feedline, the size of the I-antenna is 20.4 × 5.2 mm2, which operates in the (3.4–3.65 GHz) band. Moreover, our method obtained an envelope correlation coefficient (ECC) of <0.01 and an ergodic channel capacity of 43.50 bps/Hz. The ECC and ergodic channel capacity are important metrics for evaluating MIMO system performance. Results indicate that the proposed antenna system is a good option to be used in 5G mobile phone applications

Eight Element MIMO Antenna Array with Tri-Band Response for Modern Smartphones

This article presents an eight-element tri-band Multiple Input Multiple Output (MIMO) antenna system for future handheld devices. The suggested antenna system consists of a main and sideboards. The feed lines are connected on the main board while the antennas are placed on sideboards, two on each side separately. The total dimension of the main board is 150×75 mm2, and the sideboard is 150×7 mm2. The antenna resonates at three distinct 5G allocated bands of 3.1-3.7 GHz, 4.47-4.91 GHz, and 5.5-6.0 GHz with impedance bandwidths of 600 MHz, 440 MHz, and 450 MHz, respectively. The antenna system provides pattern and spatial diversity characteristics with radiation and total efficiency of 78% and 62% and peak gain of 5.8 dBi. The MIMO system is fabricated, and the measured results are found to be in good agreement with the simulations. The isolation among radiating elements in all resonating bands is found to be >16 dB. The vital MIMO performance parameters such as envelope correlation coefficient (ECC) is less than 0.2 for any two antenna array meeting the required standard of less than 0.5 alongside the mean effective gain or MEG ratio of any two antenna meeting the required standard of less than 3 dB for power balance and optimal diversity. The Channel Capacity (CC) is found to be 41.1 bps/Hz, approximately 3 times that of 2× 2 MIMO operations

Association of respiratory symptoms and lung function with occupation in the multinational Burden of Obstructive Lung Disease (BOLD) study

Background Chronic obstructive pulmonary disease has been associated with exposures in the workplace. We aimed to assess the association of respiratory symptoms and lung function with occupation in the Burden of Obstructive Lung Disease study. Methods We analysed cross-sectional data from 28 823 adults (≥40 years) in 34 countries. We considered 11 occupations and grouped them by likelihood of exposure to organic dusts, inorganic dusts and fumes. The association of chronic cough, chronic phlegm, wheeze, dyspnoea, forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1)/FVC with occupation was assessed, per study site, using multivariable regression. These estimates were then meta-analysed. Sensitivity analyses explored differences between sexes and gross national income. Results Overall, working in settings with potentially high exposure to dusts or fumes was associated with respiratory symptoms but not lung function differences. The most common occupation was farming. Compared to people not working in any of the 11 considered occupations, those who were farmers for ≥20 years were more likely to have chronic cough (OR 1.52, 95% CI 1.19–1.94), wheeze (OR 1.37, 95% CI 1.16–1.63) and dyspnoea (OR 1.83, 95% CI 1.53–2.20), but not lower FVC (β=0.02 L, 95% CI −0.02–0.06 L) or lower FEV1/FVC (β=0.04%, 95% CI −0.49–0.58%). Some findings differed by sex and gross national income. Conclusion At a population level, the occupational exposures considered in this study do not appear to be major determinants of differences in lung function, although they are associated with more respiratory symptoms. Because not all work settings were included in this study, respiratory surveillance should still be encouraged among high-risk dusty and fume job workers, especially in low- and middle-income countries.publishedVersio

Cohort Profile: Burden of Obstructive Lung Disease (BOLD) study

The Burden of Obstructive Lung Disease (BOLD) study was established to assess the prevalence of chronic airflow obstruction, a key characteristic of chronic obstructive pulmonary disease, and its risk factors in adults (≥40 years) from general populations across the world. The baseline study was conducted between 2003 and 2016, in 41 sites across Africa, Asia, Europe, North America, the Caribbean and Oceania, and collected high-quality pre- and post-bronchodilator spirometry from 28 828 participants. The follow-up study was conducted between 2019 and 2021, in 18 sites across Africa, Asia, Europe and the Caribbean. At baseline, there were in these sites 12 502 participants with high-quality spirometry. A total of 6452 were followed up, with 5936 completing the study core questionnaire. Of these, 4044 also provided high-quality pre- and post-bronchodilator spirometry. On both occasions, the core questionnaire covered information on respiratory symptoms, doctor diagnoses, health care use, medication use and ealth status, as well as potential risk factors. Information on occupation, environmental exposures and diet was also collected

System for Tissue Marking and Treatment

The system for marking the surface of tissue, for example in the body of a patient, comprises a delivery means with a head for treating a determined zone and a marking means for delivering a marker, wherein said delivery and marking means are in close proximity such that the marker is delivered substantially to the zone compressed by the head of the delivery means

Screening of the factors influencing frictional interactions between a cylindrical tip and the cardiac wall using factorial analysis

Knowledge of frictional forces acting on the tips of minimally invasive medical devices is important in the design and simulation of such devices. Moreover, several studies have shown that uncontrolled frictional forces can induce damage to organs. The goal of this study is to empirically investigate the dominant factors affecting frictional forces between a bovine cardiac tissue and a catheters tip. A dedicated apparatus is developed to reproduce the sliding contact between a cylindrical element and the cardiac tissue. In this paper, we utilize the design of experiment (DOE) approach to study friction. Factorial designs (FD) are used to reduce the number of experiments without reducing the information that could be extracted. Twelve factors were selected to represent the main parameters that could potentially affect friction. These factors are of physical, geometrical, physiological and temporal nature. As a result of 4 factorial designs representing a set of 128 experiments, we studied the impact on friction of the 12 parameters as well as the interactions between them. As expected, the normal force applied on the cylindrical tip is the dominant factor affecting the friction force. The remaining significant effects are the cylinder pitch angle, tissue physiological state and the pressure applied on the cardiac tissue expressed in cylinder dimensions. This study gives some guidelines to minimize and control friction interactions between a cylindrical tip and a tissue

Design of Microwave Antenna Array for Imaging of Multiphase Flows in Polypropylene Pipes

The oil and gas industry requires accurate sensors to control fluid flow in pipelines during the production process from horizontal and near horizontal wells. The extracted crude oil is usually a multiphase mixture of oil, water, and gas, and the accurate measurement of the ratio of each multiphase within the pipeline is an important parameter to manage wells efficiently by maximizing the hydrocarbons that can be extracted. Various methods have been developed for determining the phase ratio including mechanical, optical, X-ray or gamma ray, ultrasound, nuclear magnetic resonance (NMR), and rarely microwave techniques. However, these methods do not permit the knowledge of the real-time evolution of the phase ratio and are less precise. Here, we propose and develop by simulation two microwave systems, in horizontal and vertical polarizations, to choose the optimal configuration for crude pipeline imaging applications. First, the pipeline containing crude oil was modeled and its thermal and dielectric properties are proposed. Then, the antennas array performances were optimized and assembled to the pipeline. Different numbers of antenna elements were successfully investigated using CST simulation in both vertical and horizontal polarizations to find the optimal number of antenna elements for the pipeline applications