Validity of the 1984 Interim Guidelines on Airborne Ultrasound and Gaps in the Current Knowledge

ABSTRACT

Airborne ultrasound is used for various purposes both in industrial and public settings, as well as being produced as a by-product by a range of sources. The International Radiation Protection Association (IRPA) published interim guidelines on limiting human exposure to airborne ultrasound in 1984, based on the limited scientific evidence that was available at that time. In order to investigate whether research since 1984 requires the development of revised exposure guidelines we considered (a) within the context of ultrasound exposure the relevance to health of the biological endpoints/mechanisms listed in the IRPA guidelines, (b) the validity of the exposure limits, and (c) whether there are biological endpoints/mechanisms not covered in the guidelines. The analysis of the available evidence showed that the biological endpoints that form the basis of the guidelines are relevant to health and the guidelines provide limits of exposure based on the evidence that was available at the time. However, the IRPA limits and their associated dosimetry were based on limited evidence, which may not be considered as scientifically substantiated. Further, there is no substantiated evidence of biological endpoints/mechanisms not covered by the IRPA guidelines. These two observations could mean that IRPA's limits are too low or too high. Research since the IRPA guidelines has made some improvements in the knowledge base, but there are still significant data gaps that need to be resolved before a formal revision of the guidelines can be made by ICNIRP, including research needs related to health outcomes and improved dosimetry. This statement makes a number of recommendations for future research on airborne ultrasound.

Projection of future heat-related morbidity in three metropolitan prefectures of Japan based on large ensemble simulations of climate change under 2 °C global warming scenarios

Recently, global warming has become a prominent topic, including its impacts on human health. The number of heat illness cases requiring ambulance transport has been strongly linked to increasing temperature and the frequency of heat waves. Thus, a potential increase in the number of cases in the future is a concern for medical resource management. In this study, we estimated the number of heat illness cases in three prefectures of Japan under 2 °C global warming scenarios, approximately corresponding to the 2040s. Based on the population composition, a regression model was used to estimate the number of heat illness cases with an input parameter of time-dependent meteorological ambient temperature or computed thermophysiological response of test subjects in large-scale computation. We generated 504 weather patterns using 2 °C global warming scenarios. The large-scale computational results show that daily amount of sweating increased twice and the core temperature increased by maximum 0.168 °C, suggesting significant heat strain. According to the regression model, the estimated number of heat illness cases in the 2040s of the three prefectures was 1.90 (95%CI: 1.35-2.38) times higher than that in the 2010s. These computational results suggest the need to manage ambulance services and medical resource allocation, including intervention for public awareness of heat illnesses. This issue will be important in other aging societies in near future.

ICNIRP Statement on Short Wavelength Light Exposure from Indoor Artificial Sources and Human Health

ABSTRACT

Concerns have been raised about the possibility of effects from exposure to short wavelength light (SWL), defined here as 380-550 nm, on human health. The spectral sensitivity of the human circadian timing system peaks at around 480 nm, much shorter than the peak sensitivity of daytime vision (i.e., 555 nm). Some experimental studies have demonstrated effects on the circadian timing system and on sleep from SWL exposure, especially when SWL exposure occurs in the evening or at night. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has identified a lack of consensus among public health officials regarding whether SWL from artificial sources disrupts circadian rhythm, and if so, whether SWL-disrupted circadian rhythm is associated with adverse health outcomes. Systematic reviews of studies designed to examine the effects of SWL on sleep and human health have shown conflicting results. There are many variables that can affect the outcome of these experimental studies. One of the main problems in earlier studies was the use of photometric quantities as a surrogate for SWL exposure. Additionally, the measurement of ambient light may not be an accurate measure of the amount of light impinging on the intrinsically photosensitive retinal ganglion cells, which are now known to play a major role in the human circadian timing system. Furthermore, epidemiological studies of long-term effects of chronic SWL exposure per se on human health are lacking. ICNIRP recommends that an analysis of data gaps be performed to delineate the types of studies needed, the parameters that should be addressed, and the methodology that should be applied in future studies so that a decision about the need for exposure guidelines can be made. In the meantime, ICNIRP supports some recommendations for how the quality of future studies might be improved.

Sensitivity of Electrocardiogram on Electrode-Pair Locations for Wearable Devices: Computational Analysis of Amplitude and Waveform Distortion

An electrocardiogram (ECG) is used to observe the electrical activity of the heart via electrodes on the body surface. Recently, an ECG with fewer electrodes, such as a bipolar ECG in which two electrodes are attached to the chest, has been employed as wearable devices. However, the effect of different geometrical factors and electrode-pair locations on the amplitude and waveform of ECG signals remains unclear. In this study, we computationally evaluated the effects of body morphology, heart size and orientation, and electrode misalignment on ECG signals for 48 scenarios using 35 bipolar electrode pairs (1680 waveforms) with a dynamic time warping (DTW) algorithm. It was observed that the physique of the human body model predominantly affected the amplitude and waveform of the ECG signals. A multivariate analysis indicated that the heart-electrode distance and the solid angle of the heart from the electrode characterized the amplitude and waveform of the ECG signals, respectively. Furthermore, the electrode locations for less individual variability and less waveform distortion were close to the location of electrodes V2 and V3 in the standard 12-lead. These findings will facilitate the placement of ECG electrodes and interpretation of the measured ECG signals for wearable devices.

Individual and group-level optimization of electric field in deep brain region during multichannel transcranial electrical stimulation

Electrode montage optimization for transcranial electric stimulation (tES) is a challenging topic for targeting a specific brain region. Targeting the deep brain region is difficult due to tissue inhomogeneity, resulting in complex current flow. In this study, a simplified protocol for montage optimization is proposed for multichannel tES (mc-tES). The purpose of this study was to reduce the computational cost for mc-tES optimization and to evaluate the mc-tES for deep brain regions. Optimization was performed using a simplified protocol for montages under safety constraints with 20 anatomical head models. The optimization procedure is simplified using the surface EF of the deep brain target region, considering its small volume and non-concentric distribution of the electrodes. Our proposal demonstrated that the computational cost was reduced by >90%. A total of six-ten electrodes were necessary for robust EF in the target region. The optimization with surface EF is comparable to or marginally better than using conventional volumetric EF for deep brain tissues. An electrode montage with a mean injection current amplitude derived from individual analysis was demonstrated to be useful for targeting the deep region at the group level. The optimized montage and injection current were derived at the group level. Our proposal at individual and group levels showed great potential for clinical application.

The thermal sensation threshold and its reliability induced by the exposure to 28 GHz millimeter-wave

The application of 28 GHz millimeter-wave is prevalent owing to the global spread of fifth-generation wireless communication systems. Its thermal effect is a dominant factor which potentially causes pain and tissue damage to the body parts exposed to the millimeter waves. However, the threshold of this thermal sensation, that is, the degree of change in skin temperature from the baseline at which the first subjective response to the thermal effects of the millimeter waves occurs, remains unclear. Here, we investigated the thermal sensation threshold and assessed its reliability when exposed to millimeter waves. Twenty healthy adults were exposed to 28 GHz millimeter-wave on their left middle fingertip at five levels of antenna input power: 0.2, 1.1, 1.6, 2.1, and 3.4 W (incident power density: 27-399 mW/cm2). This measurement session was repeated twice on the same day to evaluate the threshold reliability. The intraclass correlation coefficient (ICC) and Bland-Altman analysis were used as proxies for the relative and absolute reliability, respectively. The number of participants who perceived a sensation during the two sessions at each exposure level was also counted as the perception rate. Mean thermal sensation thresholds were within 0.9°C-1.0°C for the 126-399 mW/cm2 conditions, while that was 0.2°C for the 27 mW/cm2 condition. The ICCs for the threshold at 27 and 126 mW/cm2 were interpreted as poor and fair, respectively, while those at higher exposure levels were moderate to substantial. Apart from a proportional bias in the 191 mW/cm2 condition, there was no fixed bias. All participants perceived a thermal sensation at 399 mW/cm2 in both sessions, and the perception rate gradually decreased with lower exposure levels. Importantly, two-thirds of the participants answered that they felt a thermal sensation in both or one of the sessions at 27 mW/cm2, despite the low-temperature increase. These results suggest that the thermal sensation threshold is around 1.0°C, consistent across exposure levels, while its reliability increases with higher exposure levels. Furthermore, the perception of thermal sensation may be inherently ambiguous owing to the nature of human perception.

High-resolution EEG source localization in personalized segmentation-free head model with multi-dipole fitting

Objective. Electroencephalograms (EEGs) are often used to monitor brain activity. Several source localization methods have been proposed to estimate the location of brain activity corresponding to EEG readings. However, only a few studies evaluated source localization accuracy from measured EEG using personalized head models in a millimeter resolution. In this study, based on a volume conductor analysis of a high-resolution personalized human head model constructed from magnetic resonance images, a finite difference method was used to solve the forward problem and to reconstruct the field distribution.Approach. We used a personalized segmentation-free head model developed using machine learning techniques, in which the abrupt change of electrical conductivity occurred at the tissue interface is suppressed. Using this model, a smooth field distribution was obtained to address the forward problem. Next, multi-dipole fitting was conducted using EEG measurements for each subject (N= 10 male subjects, age: 22.5 ± 0.5), and the source location and electric field distribution were estimated.Main results.For measured somatosensory evoked potential for electrostimulation to the wrist, a multi-dipole model with lead field matrix computed with the volume conductor model was found to be superior than a single dipole model when using personalized segmentation-free models (6/10). The correlation coefficient between measured and estimated scalp potentials was 0.89 for segmentation-free head models and 0.71 for conventional segmented models. The proposed method is straightforward model development and comparable localization difference of the maximum electric field from the target wrist reported using fMR (i.e. 16.4 ± 5.2 mm) in previous study. For comparison, DUNEuro based on sLORETA was (EEG: 17.0 ± 4.0 mm). In addition, somatosensory evoked magnetic fields obtained by Magnetoencephalography was 25.3 ± 8.5 mm using three-layer sphere and sLORETA.Significance. For measured EEG signals, our procedures using personalized head models demonstrated that effective localization of the somatosensory cortex, which is located in a non-shallower cortex region. This method may be potentially applied for imaging brain activity located in other non-shallow regions.

Small effects of electric field on motor cortical excitability following anodal tDCS

The dose-response characteristics of transcranial direct current stimulation (tDCS) remain uncertain but may be related to variability in brain electric fields due to individual anatomical factors. Here, we investigated whether the electric fields influence the responses to motor cortical tDCS. In a randomized cross-over design, 21 participants underwent 10 min of anodal tDCS with 0.5, 1.0, 1.5, or 2.0 mA or sham. Compared to sham, all active conditions increased the size of motor evoked potentials (MEP) normalized to the pre-tDCS baseline, irrespective of anterior or posterior magnetic test stimuli. The electric field calculated in the motor cortex of each participant had a nonlinear effect on the normalized MEP size, but its effects were small compared to those of other participant-specific factors. The findings support the efficacy of anodal tDCS in enhancing the MEP size but do not demonstrate any benefits of personalized electric field modeling in explaining tDCS response variability.

Modulation of pain perception through transcranial alternating current stimulation and its nonlinear relationship with the simulated electric field magnitude

BACKGROUND

Oscillatory activities observed in multiple regions are closely associated with the experience of pain. Specifically, oscillatory activities within the theta- and beta-frequency bands, observed in the left dorsolateral prefrontal cortex (DLPFC), have been implicated in pain perception among healthy individuals and those with chronic pain. However, their physiological significance remains unclear.

METHODS

We explored the modulation of pain perception in healthy individuals by theta- and beta-band transcranial alternating current stimulation (tACS) over the left DLPFC and examined the relationship between the modulation effect and magnitude of the electric field elicited by tACS in the left DLPFC using computational simulation.

RESULTS

Our findings revealed that both theta- and beta-tACS increased the heat pain threshold during and after stimulation. Notably, the simulated electric field magnitude in the left DLPFC exhibited an inverted U-shaped relationship with the pain modulation effect for theta-tACS.

CONCLUSIONS

Our study findings suggested that there would be an optimal electric field strength to produce a high analgesic effect for theta-tACS.

SIGNIFICANCE

The application of theta- and beta-tACS interventions targeting the left DLPFC might facilitate the treatment of chronic pain. Furthermore, the attainment of effective pain modulation via theta-tACS over the DLPFC warrants the use of optimal stimulus intensity.

Effect of baseline urinary glucose levels on the relationship between sodium-glucose cotransporter 2 inhibitors and serum uric acid in Japanese patients with type 2 diabetes mellitus

In patients with type 2 diabetes mellitus (T2DM), controlling serum uric acid (SUA) and blood glucose levels is important. Moreover, sodium-glucose cotransporter 2 (SGLT2) inhibitors decrease SUA levels by accelerating urinary uric acid excretion. We investigated the effect of baseline urinary glucose levels on the relationship between SGLT2 inhibitors and SUA levels. We conducted a retrospective observational study using the electronic medical records of patients with T2DM of Kindai University Nara Hospital (April 2013 to March 2022). We divided the patients into two groups according to their baseline urinary glucose levels: the N-UG group, which included patients with negative urinary glucose strip test results (-), and the P-UG group, which included patients with positive urinary glucose strip test results (± or more). The changes in SUA levels before and after SGLT2 inhibitor administration were investigated. For comparison, the changes in SUA levels before and after the prescription of antidiabetic agents, excluding SGLT2 inhibitors, were also investigated. Our results revealed that SGLT2 inhibitors significantly decreased the SUA levels in patients in the N-UG group but tended to decrease its levels in those in the P-UG group. Regardless of the urinary glucose status at baseline, the administration of SGLT2 inhibitors may be useful for patients with T2DM to prevent the complications of hyperuricemia.

Association of nuclear cataract prevalence with UV radiation and heat load in lens of older people -five city study

Epidemiological studies have reported that the frequency of nuclear cataracts (NUCs) is high among the elderly and in tropical countries. Ultraviolet (UV) irradiation and lens temperature are considered as key physical contributors, although their precise quantification is difficult. The aim of this study is to investigate the association of NUC prevalence with UV irradiation and heat load. First, we assessed the lens temperature using thermodynamic modeling considering the thermophysiological response. We then conducted a multivariate linear regression analysis for the epidemiological analysis of NUC prevalence across five cities. A strong correlation was observed between NUC prevalence and the combined effects of UV irradiation and cumulative equivalent minutes at 43 °C (CEM43°C) derived from the computed lens temperature (adjusted R2 = 0.933, p < 0.0001). Heat load significantly contributed to the prevalence at 52%, surpassing the contributions of UV irradiation (31%) and the decline in DNA repair capacity in the lens (17%). These results suggested that both UV radiation and heat load are associated with NUC, with heat load contributing more. Our findings provided important implications for future interventions, particularly in the context of global warming.

Tensor-conductance model for reducing the computational artifact in target tissue for low-frequency dosimetry

Objective.In protecting human from low-frequency (<100 kHz) exposure, an induced electric field strength is used as a physical quantity for assessment. However, the computational assessment suffers from a staircasing error because of the approximation of curved boundary discretized with cubic voxels. The international guidelines consider an additional reduction factor of 3 when setting the limit of external field strength computed from the permissible induced electric field. Here, a new method was proposed to reduce the staircasing error considering the tensor conductance in human modeling for low-frequency dosimetry.Approach.We proposed a tensor-based conductance model, which was developed on the basis of the filling ratio and the direction of the tissue interface to satisfy the electric field boundary condition and reduce staircasing errors in the target tissue of a voxel human model.Main results.The proposed model was validated using two-layer nonconcentric cylindrical and spherical models with different conductivity contrasts. A comparison of induced electric field strengths with solutions obtained using an analytical formula and finite element method simulation indicated that for a wide range of conductivity ratios, staircasing errors were reduced compared with a conventional scalar-potential finite-difference method. The induced electric field in a simple anatomical head model using our approach was in good agreement with finite element method for exposure to uniform magnetic field exposure and that from coil, simulating transcranial magnetic stimulation.Significance.The proposed tensor-conductance model demonstrated that the staircasing error in an inner target tissue of a voxel human body can be reduced. This finding can be used for the electromagnetic compliance assessment and dose evaluation in electric or magnetic stimulation at low frequencies.

Excessive whole-body exposure to 28 GHz quasi-millimeter wave induces thermoregulation accompanied by a change in skin blood flow proportion in rats

Introduction

Limited information is available on the biological effects of whole-body exposure to quasi-millimeter waves (qMMW). The aim of the present study was to determine the intensity of exposure to increase body temperature and investigate whether thermoregulation, including changes in skin blood flow, is induced in rats under whole-body exposure to qMMW.

Methods

The backs of conscious rats were extensively exposed to 28 GHz qMMW at absorbed power densities of 0, 122, and 237 W/m2 for 40 minutes. Temperature changes in three regions (dorsal and tail skin, and rectum) and blood flow in the dorsal and tail skin were measured simultaneously using fiber-optic probes.

Results

Intensity-dependent temperature increases were observed in the dorsal skin and the rectum. In addition, skin blood flow was altered in the tail but not in the dorsum, accompanied by an increase in rectal temperature and resulting in an increase in tail skin temperature.

Discussion

These findings suggest that whole-body exposure to qMMW drives thermoregulation to transport and dissipate heat generated on the exposed body surface. Despite the large differences in size and physiology between humans and rats, our findings may be helpful for discussing the operational health-effect thresholds in the standardization of international exposure guidelines.

Population-Level Immunity for Transient Suppression of COVID-19 Waves in Japan from April 2021 to September 2022

Multiple COVID-19 waves have been observed worldwide, with varying numbers of positive cases. Population-level immunity can partly explain a transient suppression of epidemic waves, including immunity acquired after vaccination strategies. In this study, we aimed to estimate population-level immunity in 47 Japanese prefectures during the three waves from April 2021 to September 2022. For each wave, characterized by the predominant variants, namely, Delta, Omicron, and BA.5, the estimated rates of population-level immunity in the 10-64-years age group, wherein the most positive cases were observed, were 20%, 35%, and 45%, respectively. The number of infected cases in the BA.5 wave was inversely associated with the vaccination rates for the second and third injections. We employed machine learning to replicate positive cases in three Japanese prefectures to validate the reliability of our model for population-level immunity. Using interpolation based on machine learning, we estimated the impact of behavioral factors and vaccination on the fifth wave of new positive cases that occurred during the Tokyo 2020 Olympic Games. Our computational results highlighted the critical role of population-level immunity, such as vaccination, in infection suppression. These findings underscore the importance of estimating and monitoring population-level immunity to predict the number of infected cases in future waves. Such estimations that combine numerical derivation and machine learning are of utmost significance for effective management of medical resources, including the vaccination strategy.

Predicting habitual water intake from lifestyle questions

OBJECTIVE

Previous studies have used selective recall and descriptive dietary record methods, requiring considerable effort for assessing food and water intake. This study created a simplified lifestyle questionnaire to predict habitual water intake (SQW), accurately and quickly assessing the habitual water intake. We also evaluated the validity using descriptive dietary records as a cross-sectional study.

SUBJECTS AND METHODS

First, we used crowdsourcing and machine learning to collect data, predict water intake records, and create questionnaires. We collected 305 lifestyle-related questions as predictor variables and selective recall methods for assessing water intake as an outcome variable. Random forests were used for the machine learning models because of their interpretability and accurate estimation. Random forest and single regression correlation analysis were augmented by the synthetic minority oversampling that trained the model. We separated the data by sex and evaluated our model using unseen hold-out testing data, predicting the individual and overall habitual water intake from various sources, including non-alcoholic beverages, alcohol, and food.

RESULTS

We found a 0.60 Spearman's correlation coefficient for total water intake between the predicted and the selective recall method values, reflecting the target value to be achieved. This question set was then used for feasibility tests. The descriptive dietary record method helped to obtain a ground-truth value. We categorized the data by gender, season, and source: non-alcoholic beverages, alcohol, food, and total water intake, and the correlation was confirmed. Consequently, our results showed a Pearson's correlation coefficient of 0.50 for total water intake between the predicted and the selective recall method values.

CONCLUSIONS

We hypothesize that dissemination of SQW can lead to better health management by easily determining the habitual water intake.

Characteristics of current perception produced by intermediate-frequency contact currents in healthy adults

Introduction

Contact electrical currents in humans stimulate peripheral nerves at frequencies of <100 kHz, producing sensations such as tingling. At frequencies above 100 kHz, heating becomes dominant, resulting in a sensation of warmth. When the current amplitude exceeds the threshold, the sensation results in discomfort or pain. In international guidelines and standards for human protection from electromagnetic fields, the limit for the contact current amplitude has been prescribed. Although the types of sensations produced by contact current at low frequencies, i.e., approximately 50-60 Hz, and the corresponding perception thresholds have been investigated, there is a lack of knowledge about those in the intermediate-frequency band-particularly from 100 kHz to 10 MHz.

Methods

In this study, we investigated the current-perception threshold and types of sensations for 88 healthy adults (range: 20-79 years old) with a fingertip exposed to contact currents at 100 kHz, 300 kHz, 1 MHz, 3 MHz, and 10 MHz.

Results

The current perception thresholds at frequencies ranging from 300 kHz to 10 MHz were 20-30% higher than those at 100 kHz (p < 0.001). In addition, a statistical analysis revealed that the perception thresholds were correlated with the age or finger circumference: older participants and those with larger finger circumferences exhibited higher thresholds. At frequencies of ≥300 kHz, the contact current mainly produced a warmth sensation, which differed from the tingling/pricking sensation produced by the current at 100 kHz.

Discussion

These results indicate that there exists a transition of the produced sensations and their perception threshold between 100 kHz and 300 kHz. The findings of this study are useful for revising the international guidelines and standards for contact currents at intermediate frequencies.

Clinical trial registration

https://center6.umin.ac.jp/cgi-open-bin/icdr_e/ctr_view.cgi?recptno=R000045660, identifier UMIN 000045213.

Computation of group-level electric field in lower limb motor area for different tDCS montages

OBJECTIVE

Transcranial direct current stimulation (tDCS) injects a weak electric current into the brain via electrodes attached to the scalp to modulate cortical excitability. tDCS is used to rebalance brain activity between affected and unaffected hemispheres in rehabilitation. However, a systematic quantitative evaluation of tDCS montage is not reported for the lower limbs. In this study, we computationally investigated the generated electric field intensity, polarity, and co-stimulation of cortical areas for lower limb targeting using high-resolution head models.

METHODS

Volume conductor models have thus been employed to estimate the electric field in the brain. A total of 18 head models of healthy subjects were used to calculate the group-level electric fields generated from four montages of tDCS for modulation of lower limbs.

RESULTS

C1-C2 montage delivered higher electric field intensities while reaching deeper regions of the lower-limb motor area. It produced a uniform polarization on the same hemisphere target with comparable intensities between hemispheres but with higher variability.

CONCLUSIONS

Proper montage selection allows reaching deeper regions of the lower-limb motor area with uniform polarization.

SIGNIFICANCE

First systematic computational study providing support to tDCS experimental studies using montages for the lower limb while considering polarity factor for balancing brain activity.

The Effects of Time Window-Averaged Mobility on Effective Reproduction Number of COVID-19 Viral Variants in Urban Cities

During epidemics, the estimation of the effective reproduction number (ERN) associated with infectious disease is a challenging topic for policy development and medical resource management. The emergence of new viral variants is common in widespread pandemics including the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A simple approach is required toward an appropriate and timely policy decision for understanding the potential ERN of new variants is required for policy revision. We investigated time-averaged mobility at transit stations as a surrogate to correlate with the ERN using the data from three urban prefectures in Japan. The optimal time windows, i.e., latency and duration, for the mobility to relate with the ERN were investigated. The optimal latency and duration were 5-6 and 8 days, respectively (the Spearman's ρ was 0.109-0.512 in Tokyo, 0.365-0.607 in Osaka, and 0.317-0.631 in Aichi). The same linear correlation was confirmed in Singapore and London. The mobility-adjusted ERN of the Alpha variant was 15-30%, which was 20-40% higher than the original Wuhan strain in Osaka, Aichi, and London. Similarly, the mobility-adjusted ERN of the Delta variant was 20%-40% higher than that of the Wuhan strain in Osaka and Aichi. The proposed metric would be useful for the proper evaluation of the infectivity of different SARS-CoV-2 variants in terms of ERN as well as the design of the forecasting system.

Selective stimulation of nociceptive small fibers during intraepidermal electrical stimulation: Experiment and computational analysis

Electrical stimulation of skin nociceptors is gaining attention in pain research and peripheral neuropathy diagnosis. However, the optimal parameters for selective stimulation are still difficult to determine because they require simultaneous characterization of the electrical response of small fibers (Aδ- and C-fibers). In this study, we measured the in vivo electrical threshold responses of small fibers to train-pulse stimulation in humans for the first time. We also examined selective stimulation via a computational model, which combines electrical analysis, and terminal fiber and synaptic models, including the first cutaneous pain C-fiber model. Selective stimulation of small fibers is performed by injecting train-pulse stimulation via coaxial electrodes with an intraepidermal needle tip at varying pulse counts and frequencies. The activation Aδ- or C-fibers was discriminated from the differences in reaction time. Aδ-fiber elicited a pinpricking sensation with a mean reaction time of 0.522 s, and C-fiber elicited a tingling sensation or slight burning itch with a mean reaction time of 1.243 s. The implemented multiscale electrical model investigates synaptic effects while considering stimulation waveform characteristics. Experimental results showed that perception thresholds decreased with the number of consecutive pulses and frequency up to convergence (five pulses or 70 Hz) during the selective stimulation of Aδ- and C-fibers. Considering the synaptic properties, the optimal stimulus conditions for selective stimulation of Aδ- vs. C-fibers were train of at least four pulses and a frequency of 40-70 Hz at a pulse width of 1 ms. The experimental results were modeled with high fidelity by incorporating temporal synaptic effects into the computational model. Numerical analysis revealed terminal axon thickness to be the most important biophysical factor affecting threshold variability. The computational model can be used to estimate perception thresholds while understanding the mechanisms underlying the selective stimulation of small fibers. The parameters derived here are important in exploring selective stimulation between Aδ- and C-fibers for diagnosing neuropathies.

Mapping Brain Motor Functions Using Transcranial Magnetic Stimulation with a Volume Conductor Model and Electrophysiological Experiments

Transcranial magnetic stimulation (TMS) activates brain cells in a noninvasive manner and can be used for mapping brain motor functions. However, the complexity of the brain anatomy prevents the determination of the exact location of the stimulated sites, resulting in the limitation of the spatial resolution of multiple targets. The aim of this study is to map two neighboring muscles in cortical motor areas accurately and quickly. Multiple stimuli were applied to the subject using a TMS stimulator to measure the motor-evoked potentials (MEPs) in the corresponding muscles. For each stimulation condition (coil location and angle), the induced electric field (EF) in the brain was computed using a volume conductor model for an individualized head model of the subject constructed from magnetic resonance images. A post-processing method was implemented to determine a TMS hotspot using EF corresponding to multiple stimuli, considering the amplitude of the measured MEPs. The dependence of the computationally estimated hotspot distribution on two target muscles was evaluated (n = 11). The center of gravity of the first dorsal interosseous cortical representation was lateral to the abductor digiti minimi by a minimum of 2 mm. The localizations were consistent with the putative sites obtained from previous EF-based studies and fMRI studies. The simultaneous cortical mapping of two finger muscles was achieved with only several stimuli, which is one or two orders of magnitude smaller than that in previous studies. Our proposal would be useful in the preoperative mapping of motor or speech areas to plan brain surgery interventions.

Estimation of the number of heat illness patients in eight metropolitan prefectures of Japan: Correlation with ambient temperature and computed thermophysiological responses

The number of patients with heat illness transported by ambulance has been gradually increasing due to global warming. In intense heat waves, it is crucial to accurately estimate the number of cases with heat illness for management of medical resources. Ambient temperature is an essential factor with respect to the number of patients with heat illness, although thermophysiological response is a more relevant factor with respect to causing symptoms. In this study, we computed daily maximum core temperature increase and daily total amount of sweating in a test subject using a large-scale, integrated computational method considering the time course of actual ambient conditions as input. The correlation between the number of transported people and their thermophysiological temperature is evaluated in addition to conventional ambient temperature. With the exception of one prefecture, which features a different Köppen climate classification, the number of transported people in the remaining prefectures, with a Köppen climate classification of Cfa, are well estimated using either ambient temperature or computed core temperature increase and daily amount of sweating. For estimation using ambient temperature, an additional two parameters were needed to obtain comparable accuracy. Even using ambient temperature, the number of transported people can be estimated if the parameters are carefully chosen. This finding is practically useful for the management of ambulance allocation on hot days as well as public enlightenment.

Effects of cerebellar transcranial direct current stimulation on upper limb motor function after stroke: study protocol for the pilot of a randomized controlled trial

Background

Transcranial direct current stimulation (tDCS) is a technique that can noninvasively modulate neural states in a targeted brain region. As cerebellar activity levels are associated with upper limb motor improvement after stroke, the cerebellum is a plausible target of tDCS. However, the effect of tDCS remains unclear. Here, we designed a pilot study to assess: (1) the feasibility of a study that aims to examine the effects of cerebellar tDCS combined with an intensive rehabilitation approach based on the concept of constraint-induced movement therapy (CIMT) and (2) the preliminary outcome of the combined approach on upper limb motor function in patients with stroke in the chronic stage.

Methods

This pilot study has a double-blind randomized controlled design. Twenty-four chronic stroke patients with mild to moderate levels of upper limb motor impairment will be randomly assigned to an active or sham tDCS group. The participants will receive 20 min of active or sham tDCS to the contralesional cerebellum at the commencement of 4 h of daily intensive training, repeatedly for 5 days per week for 2 weeks. The primary outcomes are recruitment, enrollment, protocol adherence, and retention rates and measures to evaluate the feasibility of the study. The secondary outcome is upper limb motor function which will be evaluated using the Action Research Arm Test, Fugl-Meyer Assessment, for the upper extremity and the Motor Activity Log. Additionally, neurophysiological and neuroanatomical assessments of the cerebellum will be performed using transcranial magnetic stimulation and magnetic resonance imaging. These assessments will be conducted before, at the middle, and after the 2-week intervention, and finally, 1 month after the intervention. Any adverse events that occur during the study will be recorded.

Discussion

Cerebellar tDCS combined with intensive upper limb training may increase the gains of motor improvement when compared to the sham condition. The present study should provide valuable evidence regarding the feasibility of the design and the efficacy of cerebellar tDCS for upper limb motor function in patients with stroke before a future large trial is conducted.

Trial registration

This study has been registered at the Japan Registry of Clinical Trials (jRCTs042200078). Registered 17 December 2020

Assessment of incident power density in different shapes of averaging area for radio-frequency exposure above 6 GHz

Objective. The International Commission on Non-Ionizing Radiation Protection guidelines and IEEE C95.1-2019 standard for human protection from local electromagnetic field exposure above 6 GHz state that absorbed (or epithelial) power density (APD) and incident power density (IPD), averaged over a square area, are internal and external physical quantities, respectively, that set the exposure limit. Per exposure standards, the measurement procedure and evaluation of the IPD have been established in technical standards, where a circular averaging area is recommended only for non-planar surfaces in IEC/IEEE 63195-1 and -2. In this study, the effects of two averaging shapes on the APD and IPD are evaluated computationally to provide new insights from the viewpoint of exposure standards. Approach. The relation between the APD, IPD, and the steady-state temperature rise (heating factor) in rectangular and human models for exposure to a single dipole, dipole arrays, and the Gaussian beams is investigated computationally with finite-difference method. Main results. The maximum differences in the heating factor of the APD and IPD for square and circular averaging areas were 4.1% and 4.4% for the antenna–model distance >5 mm, respectively. These differences appear when the beam pattern on the model surface has an elliptical shape. For an antenna–model distance ≤5 mm and at frequencies ≤15 GHz, the heating factors for square averaging areas were not always conservative to those for circular ones (−7.8% for IPD), where only the antenna feed point are visible before beam formation. Significance. The heating factors of the APD and IPD for a circular averaging area are conservative for near-field exposure of canonical sources for frequencies up to 300 GHz, except for a beam with a significant major-to-minor axis ratio and an angle of 30°–60° to a square averaging area. This tendency would help bridge the gap between exposure and product standards.

An effective edge conductivity for reducing staircasing error in induced electric field computation for low-frequency magnetic field dosimetry

Objective In the low-frequency exposure (< 100 kHz), the induced electric field strength is used as a metric for assessment for human protection. Unlike radio-frequency exposure (> MHz), the computational assessment suffers from staircasing error in biological objects. The international guidelines consider additional reduction factor of 3 when setting the limit. Here we propose a new method to reduce the staircasing error in the skin for low-frequency magnetic field dosimetry of voxelized body models. Approach We have proposed a new method considering the filling ratio of the skin tissue to the air–skin and skin–fat interfaces to determine an effective conductivity for each voxel edge. the proposed method was applied to voxel head models exposed to a uniform magnetic field at 50 Hz. After validation using layered spherical models with several resolutions, anatomical head models are used for further verification. Main results A comparison of maximum electric field strengths with analytic solutions in two-layer sphere models suggested that the differences in the proposed approach were less than 5.6%, which was smaller than those without the proposal of 26.7%. The distribution of the skin electric field become smoother using the proposed approach, and the staircasing effects were almost unobservable from the field distributions. Significance The proposed method suggests vital implications for determining induced electric fields in the skin, which is needed to set the limit for human protection from low-frequency electromagnetic fields. The method would be useful when setting the reduction factor and limit in the exposure guidelines and standard.

Did the Tokyo Olympic Games enhance the transmission of COVID-19? An interpretation with machine learning

BACKGROUND

In the summer of 2021, the Olympic Games were held in Tokyo during the state of emergency due to the spread of COVID-19 pandemic. New daily positive cases (DPC) increased before the Olympic Games, and then decreased a few weeks after the Games. However, several cofactors influencing DPC exist; consequently, careful consideration is needed for future international events during an epidemic.

METHODS

The impact of the Olympic Games on new DPC were evaluated in the Tokyo, Osaka, and Aichi Prefectures using a well-trained and -evaluated long short-term memory (LSTM) network. In addition, we proposed a compensation method based on effective reproduction number (ERN) to assess the effect of the national holidays on the DPC.

RESULTS

During the spread phase, the estimated DPC with LSTM was 30%-60% lower than that of the observed value, but was consistent with the compensated value of the ERN for the three prefectures. During the decay phase, the estimated DPC was consistent with the observed values. The timing of the decay coincided with achievement of a fully-vaccinated rate of 10%-15% of people aged <65 years.

CONCLUSIONS

The up- and downsurge of the pandemic wave observed in July and September are likely attributable to high ERN during national holiday periods and to the vaccination effect, especially for people aged <65 years. The effect of national holidays in Tokyo was rather notable in Aichi and Osaka, which are distant from Tokyo. The effect of the Olympic Games on the spread and decay of the pandemic wave is neither dominant nor negligible due to the shifting of the national holiday dates to coincide with the Olympic Games.

AB0381 ULTRASONOGRAPHY TO PREDICT FLARE AFTER DISCONTINUATION OF BIOLOGICS IN PATIENTS WITH RHEUMATOID ARTHRITIS IN REMISSION

Background

Ultrasonography (US) has been suggested to be useful in predicting flare in patients with rheumatoid arthritis (RA) after discontinuation of biological disease-modifying antirheumatic drugs (bDMARDs).

Objectives

This study aimed to investigate whether US can predict flare after discontinuation of bDMARDs in RA patients who have achieved stringent remission criteria.

Methods

We prospectively enrolled RA patients who maintained a simplified disease activity index ≤ 3.3 and discontinued bDMARDs and measured clinical assessment and US every 2-3 months for 2 years. The US examination was performed on 40 joints using the semi-quantitative method of 0-3 on the Grey-scale (GS) and Power Doppler (PD), and the total values for each patient were used as the GS score and PD score. Joints graded as GS score ≥ 2 or PD score ≥ 1 were counted as US arthritis. In addition, tendons at 36 sites were counted with or without tendinitis/tenosynovitis to obtain a tendon score.

Results

Thirty-six patients were enrolled and two patients who dropped out early without flare were excluded from the comparative analyses. At baseline, the median GS score was 7, PD score was 0, US arthritis was 0, and tendon score was 0. The total PD score was 0 in 26 patients (72%) and it was 1 in 5 patients (14%). There were no significant differences in US findings between the relapse group (20 patients) and the non-relapse group (14 patients). Positive and negative predictive value for PD-positive findings (total PD score ≥1) were 60% and 42%, and for total PD score ≥2 were 60% and 41%, respectively.

Conclusion

The PD score in the US findings at the time of bDMARDs discontinuation was not predictive for future disease flare.

Disclosure of Interests

Takehisa Ogura Speakers bureau: AbbVie G.K, Ayako Hirata: None declared, Takaharu Kagtagiri: None declared, Yuto Takakura: None declared, Hideto Kameda Speakers bureau: AbbVie G.K., Asahi Kasei Pharma, Astellas Pharma Inc., Bristol-Myers Squibb, Chugai Pharmaceutical Co. Ltd., Eisai Co. Ltd., Eli Lilly Japan K.K., Gilead Sciences, Janssen Pharmaceutical K.K., Mitsubishi Tanabe Pharma, Novartis Pharma K.K., and Sanofi Pharma, Grant/research support from: AbbVie G.K., Asahi Kasei Pharma, Astellas Pharma Inc., Chugai Pharmaceutical Co. Ltd., Eisai Co. Ltd., Mitsubishi Tanabe Pharma, Novartis Pharma K.K., and Sanofi Pharma

Impact of heart rate reduction on recurrence after catheter ablation of persistent atrial fibrillation

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Johnson & Johnson KK

OnBehalf

OCVC Arrhythmia Investigators

Background

Predicting heart rate (HR) after restoration of sinus rhythm (SR) remains one of the challenges when performing catheter ablation (CA) of persistent atrial fibrillation (AF).

Purpose

To evaluate the association between pre-ablation HR during AF and post-ablation HR during SR, and whether the HR reduction is associated with AF recurrence.

Methods

The analysis was performed from the EARNEST-PVI trial, a randomized controlled trial designed to assess a CA strategy for persistent AF, which was conducted in the Osaka region of Japan. After excluding patients with beta-blocker prescription, a total of 216 patients (median age, 67 years; 20% female; 23% long-standing persistent AF) with AF rhythm at baseline and SR at discharge were enrolled in this study. Baseline HR during AF and post-ablation HR during SR was measured on admission and at discharge using the 12-lead electrocardiograms, respectively.

Results

There was a mild correlation between baseline HR (median 82 [interquartile range 72-95] bpm) and post-ablation HR (78 [48-117] bpm) (r = 0.27, p &lt;0.001). Reduction in HR was positively associated with baseline HR (r = 0.79, p &lt;0.001) and was negatively associated with post-ablation HR (r = - 0.37, p &lt;0.001). During the follow-up of 1 year, 56 patients (25.9%) experienced AF recurrence. HR reduction had the higher diagnostic accuracy in predicting AF recurrence than HR at baseline and HR after CA (area under the curve, 0.625; 95% confidence interval, 0.557–0.690; p = 0.003). AF recurrence rate was significantly higher in 141 patients with smaller HR reduction (cut-off, &lt;14bpm) than those with larger HR reduction (31.9% vs. 14.7%, p = 0.009). After adjustment of age, gender, long-standing persistent AF, and CA strategy, HR reduction of &lt;14 bpm was a significant predictor of AF recurrence (hazard ratio, 2.32; 95% confidence interval, 1.20–4.51; p = 0.013).

Conclusions

There was a mild correlation between HR during AF and HR after restoration of SR in patients underwent CA of persistent AF. HR reduction after restoration of SR predicted AF recurrence.

Nonequivalent After-Effects of Alternating Current Stimulation on Motor Cortex Oscillation and Inhibition: Simulation and Experimental Study

The effects of transcranial alternating current stimulation (tACS) frequency on brain oscillations and cortical excitability are still controversial. Therefore, this study investigated how different tACS frequencies differentially modulate cortical oscillation and inhibition. To do so, we first determined the optimal positioning of tACS electrodes through an electric field simulation constructed from magnetic resonance images. Seven electrode configurations were tested on the electric field of the precentral gyrus (hand motor area). We determined that the Cz-CP1 configuration was optimal, as it resulted in higher electric field values and minimized the intra-individual differences in the electric field. Therefore, tACS was delivered to the hand motor area through this arrangement at a fixed frequency of 10 Hz (alpha-tACS) or 20 Hz (beta-tACS) with a peak-to-peak amplitude of 0.6 mA for 20 min. We found that alpha- and beta-tACS resulted in larger alpha and beta oscillations, respectively, compared with the oscillations observed after sham-tACS. In addition, alpha- and beta-tACS decreased the amplitudes of conditioned motor evoked potentials and increased alpha and beta activity, respectively. Correspondingly, alpha- and beta-tACSs enhanced cortical inhibition. These results show that tACS frequency differentially affects motor cortex oscillation and inhibition.

Evaluation of Peripheral Electrostimulation Thresholds in Human Model for Uniform Magnetic Field Exposure

The external field strength according to the international guidelines and standards for human protection are derived to prevent peripheral nerve system pain at frequencies from 300-750 Hz to 1 MHz. In this frequency range, the stimulation is attributable to axon electrostimulation. One limitation in the current international guidelines is the lack of respective stimulation thresholds in the brain and peripheral nervous system from in vivo human measurements over a wide frequency range. This study investigates peripheral stimulation thresholds using a multi-scale computation based on a human anatomical model for uniform exposure. The nerve parameters are first adjusted from the measured data to fit the peripheral nerve in the trunk. From the parameters, the external magnetic field strength to stimulate the nerve was estimated. Here, the conservativeness of protection limits of the international guidelines and standards for peripheral stimulation was confirmed. The results showed a margin factor of 4-6 and 10-24 times between internal and external protection limits of Institute of Electrical and Electronics Engineers standard (IEEE C95.1) and International Commission on Non-Ionizing Radiation Protection guidelines, with the computed pain thresholds.

Time-dependent changes in serum magnesium levels in patients receiving cetuximab with low baseline serum sodium levels

Cetuximab causes electrolyte abnormalities, such as hypomagnesemia, hypokalemia, and hypocalcemia. However, little is known about the relationships between the onset of hypomagnesemia, patient background before administration, and time-dependent changes in serum magnesium levels. Therefore, we examined the patient backgrounds that influenced the onset of hypomagnesemia and the time-dependent changes in serum magnesium levels in patients receiving cetuximab. A retrospective study was performed to investigate patients with advanced or recurrent colorectal cancer or head and neck cancer, treated with a cetuximab regimen from 2012 to 2020 at Kindai University Nara Hospital. In total, 52 patients who met the inclusion criteria were enrolled in this study. The serum magnesium level was significantly lower in the hyponatremia before the administration group than in the non-hyponatremia group (p < 0.001). Univariate logistic regression analysis revealed that the baseline serum sodium levels (odds ratio [OR]: 0.741, 95% confidence interval [CI]: 0.588-0.934) and the combination of magnesium oxide tablet (OR: 0.997, 95% CI: 0.995-0.999) were one of the independent factors for hypomagnesemia. These results indicated that hyponatremia before administration may be an indicator of serum magnesium levels after administration of cetuximab. Cetuximab-induced hypomagnesemia may be predicted using baseline serum sodium levels, and hypomagnesemia may be prevented by administration of magnesium oxide tablets. Our findings provided new evidence for the management of serum magnesium levels in patients receiving cetuximab.

Reappraising the role of baseline plasma C-reactive protein levels on recurrence after catheter ablation of persistent atrial fibrillation: insight from EARNEST-PVI trial

Background

Subclinical inflammation is an important pathogenesis of developing and sustaining atrial fibrillation (AF). Because AF itself contribute to the inflammatory response, the role of baseline subclinical inflammation on AF recurrence after catheter ablation (CA) remains controversial in patients with persistent AF.

Purpose

To evaluate whether baseline plasma C-reactive protein (CRP) levels, a sensitive marker of inflammation, are associated with AF recurrence following CA.

Methods

The analysis was performed from the EARNEST-PVI trial, a randomized controlled trial designed to assess a CA strategy for persistent AF, which was conducted in the Osaka region of Japan. A total of 441 patients (median age, 67 years; 26% female; 25% long-standing persistent AF) whose plasma CRP levels were measured at baseline were included in this study.

Results

At baseline, a median (interquartile range) of plasma CRP level was 0.10 [0.06–0.19] mg/dl. Plasma CRP levels significantly increased at discharge (0.83 [0.21–1.84] mg/dl, p&lt;0.001) and decreased 1 year after CA (0.10 [0.05–0.20] mg/dl, p=0.040) compared to the baseline value. During the follow-up of 1 year, 115 patients (26%) experienced AF recurrence, and the incidence was significantly higher in 124 patients with low CRP levels at baseline (cut-off ≤0.06 mg/dl) than the other 317 patients (33.9% vs. 23.0%, p=0.017). After adjustment of age, gender, body mass index, long-standing persistent AF, CA strategy, and plasma brain natriuretic peptide levels, low plasma CRP levels was a significant predictor of AF recurrence (hazard ratio, 1.51; 95% confidence interval, 1.02–2.24; p=0.042).

Conclusions

Low plasma CRP levels at baseline predicted AF recurrence in the EARNEST-PVI trial. Reappraising the role of CRP on AF recurrence may be needed in patients with persistent AF.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Johnson & Johnson KK

Renal function and arrhythmia outcomes in persistent atrial fibrillation patients after catheter ablation: subanalysis of the EARNEST-PVI trial

Background

Atrial fibrillation (AF) reduces the renal function. Renal dysfunction and AF often coexist. Catheter ablation (CA) of persistent AF can maintain a sinus rhythm and may improve the renal function.

Purpose

We sought to elucidate whether the estimated glomerular filtration rate (eGFR) in patients with persistent AF was increased after CA, especially with the presence of an AF recurrence.

Methods

We enrolled 487 persistent AF patients whose eGFR data were available both before and 1-year after the CA out of 512 patients in the EARNEST-PVI trial.

Results

The mean age was 65±9 year and 113 patients (24.8%) had long-standing persistent AF. We compared the eGFR at baseline with that 1-year after the CA. AF recurrences were recognized in 118 patients (25.8%). The eGFR was similar between the group without recurrence and that with recurrence at baseline (without AF recurrence vs. with AF recurrence; 63.8±14.3 vs. 62.7±13.6 mL/min/1.73m2, p=0.46). In patients without AF recurrence, the G1, G2, G3a, G3b, G4, and G5 were 13 (3.8%), 198 (58.4%), 98 (28.9%), 26 (7.7%), 3 (0.9%), and 1 (0.3%), respectively at baseline. In the patients with AF recurrence, the G1, G2, G3a, G3b, G4, and G5 were 3 (2.5%), 68 (57.8%), 38 (32.2%), 6 (5.1%), 3 (2.5%), and 0 (0%), respectively at baseline. The ΔeGFR was significantly higher in the patients without AF recurrence than in those with AF recurrence (without AF recurrence vs. with AF recurrence; 5.1 [−0.3, 10.8] vs. 3.0 [−3.0, 7.6], p=0.0033). In the patients without AF recurrence, a better eGFR class at 1-year after the CA than in those before the CA was recognized in 75 patients (22.1%), while it was recognized in 19 patients (16.1%) with AF recurrences.

Conclusion

Successful catheter ablation in patients with persistent AF led to a better renal outcome.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): This study was funded by Medtronic, Johnson & Johnson, and Abbott.

Differences in quality of life improvement with pulmonary vein isolation alone vs. more extensive ablation of persistent atrial fibrillation: insights from the EARNEST-PVI trial

Background

Improving the quality of life (QoL) is one of the main purposes of catheter ablation (CA) of persistent atrial fibrillation (AF). QoL improvement in persistent AF patients has not been fully clarified. The EARNEST-PVI trial was a multi-center randomized trial comparing clinical outcomes of pulmonary vein isolation (PVI) alone and more intensive ablation in addition to PVI including complex fractionated atrial electrogram (CFAE) and linear ablation (PVI plus).

Purpose

To investigate the QoL change after persistent AF ablation and the differences between the PVI-alone strategy and the PVI plus strategy.

Methods

In the EARNEST-PVI trial, patients with persistent AF who underwent an initial catheter ablation (n=512) were randomly assigned in a 1:1 ratio to either PVI alone or PVI plus. Quality of life was assessed at baseline and at 12 months after ablation for AF using the 36-Item Short Form Health Survey. Scores were also converted to a physical health component summary (PCS), a mental health component summary (MCS) and a role/social component summary (RCS).

Results

In the EARNEST-PVI trial, the PVI alone strategy was associated with higher recurrence rate compared with the PVI plus additional ablation strategy. After excluding 68 patients for whom preoperative or postoperative QoL assessment was not available, 222 patients were evaluated respectively. Overall, significant improvements in PCS (46.2±11.4 to 48.7±11.4]), MCS (50.1±8.8 to 54.3±8.6) and RCS (44.6±13.3 to 48.6±11.3) occurred 12 months after ablation (P&lt;0.001, respectively). Although significant QoL improvement occurred in both PVI alone and PLI plus strategies, the changes in PCS was greater in the PVI-plus than that in PVI-alone (3.5±10.3 vs 1.5±10.6, P=0.04).

Conclusions

Ablation for persistent atrial fibrillation improved both physical and mental quality of life. The PVI-plus strategy showed greater improvement in physical QoL.

Funding Acknowledgement

Type of funding sources: None. QoL improvement

Coil orientation affects pain sensation during single-pulse transcranial magnetic stimulation over Broca's area

Objective

Pain sensation at the site of stimulation is a side effect of transcranial magnetic stimulation (TMS). The purpose of this study was to investigate how or whether the coil orientation affected TMS-induced pain on Broca's area (BA) or primary motor cortex (M1).

Methods

In Experiment 1, we measured pain thresholds during single-pulse TMS delivered over BA or left M1 at seven coil orientation angles (-90° to 90°, in 30° increments) relative to the posterior-anterior (PA) orientation. In Experiment 2, we evaluated subjective pain intensity when delivering TMS at an intensity of 110% of the resting motor threshold, which is commonly used in conventional TMS studies.

Results

In Experiment 1, we found a significant relationship between coil orientation and pain thresholds during BA stimulation but not M1 stimulation. During BA stimulation, pain thresholds were significantly lower when the coil orientation was 30° upward (-30° condition) relative to the PA orientation compared with 60° downward (60° condition). In Experiment 2, pain sensations were significantly stronger in the -30° condition compared with those in the 60° condition. We also confirmed that the averaged location of pain on the head in both conditions were more than 25 mm from the left lateral orbital rim.

Conclusions

The coil orientation of TMS over BA affects pain sensations. This might be attributable to the activation of nociceptors and nociceptive fibers in the muscle tissues above BA, rather than the orbicularis oculi muscle.

Significance

Although the influence of coil orientation on the TMS efficacy is unclear, this study suggests that manipulating the orientation of the TMS coil may be helpful in reducing pain when applying TMS to BA.

Novel Health Risk Alert System for Occupational Safety in Hot Environments

The last century has seen a gradual increase in global average temperatures-a phenomenon that has come to be known as global warming. The World Meteorological Organization (WMO) has reported that 2020 was one of the three warmest years on record and that the global average temperature was ~1.2°C above preindustrial (1850-1900) levels [1]. Adverse effects on health resulting from global warming are important issues to consider, as health risks associated with such extreme heat are anticipated [2]. In fact, this warming has been shown to severely limit human activity in tropical and mid-latitude regions [3], and in particular, outdoor and manual workers who are exposed to ambient heat during working hours are susceptible to increased health risks. Thus, workers should pay attention to their own physical conditions and proactively keep out of the heat to rest when uncomfortable. Additionally, supervisors must manage worker's physical conditions and schedule regular breaks. Therefore, in this trial a new integrated system was developed to notify individuals at risk based on their thermal physiology. This method uses biological and environmental information obtained directly via wearable sensors and the estimated body core temperature collected on-ground cannot be measured wirelessly and noninvasively [4].

Infectivity Upsurge by COVID-19 Viral Variants in Japan: Evidence from Deep Learning Modeling

The significant health and economic effects of COVID-19 emphasize the requirement for reliable forecasting models to avoid the sudden collapse of healthcare facilities with overloaded hospitals. Several forecasting models have been developed based on the data acquired within the early stages of the virus spread. However, with the recent emergence of new virus variants, it is unclear how the new strains could influence the efficiency of forecasting using models adopted using earlier data. In this study, we analyzed daily positive cases (DPC) data using a machine learning model to understand the effect of new viral variants on morbidity rates. A deep learning model that considers several environmental and mobility factors was used to forecast DPC in six districts of Japan. From machine learning predictions with training data since the early days of COVID-19, high-quality estimation has been achieved for data obtained earlier than March 2021. However, a significant upsurge was observed in some districts after the discovery of the new COVID-19 variant B.1.1.7 (Alpha). An average increase of 20–40% in DPC was observed after the emergence of the Alpha variant and an increase of up to 20% has been recognized in the effective reproduction number. Approximately four weeks was needed for the machine learning model to adjust the forecasting error caused by the new variants. The comparison between machine-learning predictions and reported values demonstrated that the emergence of new virus variants should be considered within COVID-19 forecasting models. This study presents an easy yet efficient way to quantify the change caused by new viral variants with potential usefulness for global data analysis.

Multiscale Computational Model Reveals Nerve Response in a Mouse Model for Temporal Interference Brain Stimulation

There has been a growing interest in the non-invasive stimulation of specific brain tissues, while reducing unintended stimulation in surrounding regions, for the medical treatment of brain disorders. Traditional methods for non-invasive brain stimulation, such as transcranial direct current stimulation (tDCS) or transcranial magnetic stimulation (TMS), can stimulate brain regions, but they also simultaneously stimulate the brain and non-brain regions that lie between the target and the stimulation site of the source. Temporal interference (TI) stimulation has been suggested to selectively stimulate brain regions by superposing two alternating currents with slightly different frequencies injected through electrodes attached to the scalp. Previous studies have reported promising results for TI applied to the motor area in mice, but the mechanisms are yet to be clarified. As computational techniques can help reveal different aspects of TI, in this study, we computationally investigated TI stimulation using a multiscale model that computes the generated interference current pattern effects in a neural cortical model of a mouse head. The results indicated that the threshold increased with the carrier frequency and that the beat frequency did not influence the threshold. It was also found that the intensity ratio between the alternating currents changed the location of the responding nerve, which is in agreement with previous experiments. Moreover, particular characteristics of the envelope were investigated to predict the stimulation region intuitively. It was found that regions with high modulation depth (| maximum| − | minimum| values of the envelope) and low minimum envelope (near zero) corresponded with the activation region obtained via neural computation.

High-Resolution EEG Source Localization in Segmentation-Free Head Models Based on Finite-Difference Method and Matching Pursuit Algorithm

Electroencephalogram (EEG) is a method to monitor electrophysiological activity on the scalp, which represents the macroscopic activity of the brain. However, it is challenging to identify EEG source regions inside the brain based on data measured by a scalp-attached network of electrodes. The accuracy of EEG source localization significantly depends on the type of head modeling and inverse problem solver. In this study, we adopted different models with a resolution of 0.5 mm to account for thin tissues/fluids, such as the cerebrospinal fluid (CSF) and dura. In particular, a spatially dependent conductivity (segmentation-free) model created using deep learning was developed and used for more realist representation of electrical conductivity. We then adopted a multi-grid-based finite-difference method (FDM) for forward problem analysis and a sparse-based algorithm to solve the inverse problem. This enabled us to perform efficient source localization using high-resolution model with a reasonable computational cost. Results indicated that the abrupt spatial change in conductivity, inherent in conventional segmentation-based head models, may trigger source localization error accumulation. The accurate modeling of the CSF, whose conductivity is the highest in the head, was an important factor affecting localization accuracy. Moreover, computational experiments with different noise levels and electrode setups demonstrate the robustness of the proposed method with segmentation-free head model.

ECG Localization Method Based on Volume Conductor Model and Kalman Filtering

The 12-lead electrocardiogram was invented more than 100 years ago and is still used as an essential tool in the early detection of heart disease. By estimating the time-varying source of the electrical activity from the potential changes, several types of heart disease can be noninvasively identified. However, most previous studies are based on signal processing, and thus an approach that includes physics modeling would be helpful for source localization problems. This study proposes a localization method for cardiac sources by combining an electrical analysis with a volume conductor model of the human body as a forward problem and a sparse reconstruction method as an inverse problem. Our formulation estimates not only the current source location but also the current direction. For a 12-lead electrocardiogram system, a sensitivity analysis of the localization to cardiac volume, tilted angle, and model inhomogeneity was evaluated. Finally, the estimated source location is corrected by Kalman filter, considering the estimated electrocardiogram source as time-sequence data. For a high signal-to-noise ratio (greater than 20 dB), the dominant error sources were the model inhomogeneity, which is mainly attributable to the high conductivity of the blood in the heart. The average localization error of the electric dipole sources in the heart was 12.6 mm, which is comparable to that in previous studies, where a less detailed anatomical structure was considered. A time-series source localization with Kalman filtering indicated that source mislocalization could be compensated, suggesting the effectiveness of the source estimation using the current direction and location simultaneously. For the electrocardiogram R-wave, the mean distance error was reduced to less than 7.3 mm using the proposed method. Considering the physical properties of the human body with Kalman filtering enables highly accurate estimation of the cardiac electric signal source location and direction. This proposal is also applicable to electrode configuration, such as ECG sensing systems.

POS1396 DAMAGE PROGRESSION OF FINGER JOINT CARTILAGE EVALUATED BY ULTRASOUND AND X-RAY IN PATIENTS WITH RHEUMATOID ARTHRITIS (RA)

Background:

Cartilage damage in RA has been evaluated by joint space narrowing (JSN) in X-ray, while it is not a direct evaluation of cartilage. Previously we have confirmed the usefulness of the direct imaging of finger joint cartilage by ultrasound (US) in patients with RA [1].

Objectives:

We aimed to examine the temporal changes of US cartilage thickness in RA patients.

Methods:

We enrolled 53 RA patients in whom the cartilage thickness of finger joints was measured by US and had radiographs of both hands at baseline and 1-year later. The cartilage of metacapophalangeal and proximal interphalangeal joints of 2nd to 5th fingers were bilaterally visualized at the middle portion from a longitudinal dorsal view. Cartilage thickness was measured from the base of the cartilage to the interface artefact at the cartilage surface by static images. In addition, the JSN of the corresponding joints was scored using a hand X-ray by van der Heijde-modified Sharp method. Continuous variables from the two groups were analyzed using the Mann-Whitney U test or Wilcoxon signed-rank test. The relationships among the continuous variables were assessed using the Spearman’s rank correlation coefficient.

Results:

The median age of the patients was 68 years and the median disease duration was 6.3 years. The sum of total cartilage thickness from 16 joints per patient ranged from 3.1 to 9.1mm (median 6.5 mm) at baseline, and it was significantly correlated with total JSN score of the same joints (ρ=-0.63, p<0.001). The cartilage thickness was inversely correlated with disease duration (rho=-0.40, p=0.003), but not associated with age nor height. The decrease in cartilage thickness over 1 year was evident in patients with persistent moderate to high disease activity by the DAS28-CRP (n=10; median -6.2%) as compared with other patients (n=43; median -1.2%, p=0.004 versus active patients).

Conclusion:

This pilot study demonstrated the progression of cartilage damage by sustained RA activity, supporting the validity and usefulness of joint cartilage thickness evaluation by ultrasound in patients with RA.

References:

[1]Ogura T, et al. Arthritis Care Res 2019 Oct 25.

Table 1.

SALIENT FEATURES OF THE 9 PATIENTS PRESENTING WITH RETINAL TOXICITY DUE TO HCQ

Sl.NoAgeGenderWeight(Kg)Primary DiagnosisDoseDuration(Years)Detection Method UsedRecommended Dose(mg/Day)Received Dose(mg/Day)Cumulative Dose(grams)FUNDUSEXAM.SD-OCTHVF10-2FAF147F58SLE2904004383RPE ChangesThinning/Photoreceptor LossDefects seen-220F46SLE2302001462Multiple Small Drusens In Paramacular AreaMultipleDrusensNormalPerifoveal autofluorescence spots-drusens323F50SLE2504001461RPE ChangesRPEDisruptionsDefects seen-430F55SLE275200731NormalNormalParacentral Scotoma-550F49RA2452005117Early Bull’s Eye MaculopathyRPEAtrophyDefects seen-672F60RA30020073010RPE AtrophyFR AbsentRPEAtrophyGeneral reduction in sensitivity-765M57.4RA2872001462RPE ChangesRPEDisruptions & Thinning NotedDefects seen-862F70RA3502002193Chorioretinal AtrophyAlteredRPEMembraneDefects seen-959M71.6RA3582002924RPE ChangesRPEDisruptionsNormal-

F:Female; M:Male; SLE:Systemic Lupus Erythematosus; RA: Rheumatoid Arthritis, FUNDUS EXAM.: Fundus Examination; SD-OCT:Spectral Domain-Optical Coherence Tomography, HVF 10-2:Humphrey Visual Field 10-2; FAF: Fundus Autofluorescence, RPE:Retinal Pigment Epithelium; FR:Foveal Reflex

Disclosure of Interests:

None declared

Influence of population density, temperature, and absolute humidity on spread and decay durations of COVID-19: A comparative study of scenarios in China, England, Germany, and Japan

In this study, we analyzed the spread and decay durations of the COVID-19 pandemic in several cities of China, England, Germany, and Japan, where the first wave has undergone decay. Differences in medical and health insurance systems, as well as in regional policies incommoded the comparison of the spread and decay in different cities and countries. The spread and decay durations in the cities of the four studied countries were reordered and calculated based on an asymmetric bell-shaped model. We acquired the values of the ambient temperature, absolute humidity, and population density to perform multivariable analysis. We found a significant correlation (p < 0.05) of the spread and decay durations with population density in the four analyzed countries. Specifically, spread duration showed a high correlation with population density and absolute humidity (p < 0.05), whereas decay duration demonstrated the highest correlation with population density, absolute humidity, and maximum temperature (p < 0.05). The effect of population density was almost nonexistent in China because of the implemented strict lockdown. Our findings will be useful in policy setting and governmental actions in the next pandemic, as well as in the next waves of COVID-19.

Impact of Proteinuria and Low eGFR on Lifetime Risk of Cardiovascular Disease Death: A Pooled Analysis of Data From the Evidence for Cardiovascular Prevention From Observational Cohorts in Japan Study

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): H20–Junkankitou [Seishuu]–Ippan–013; H23–Junkankitou [Seishuu]–Ippan–005; H26-Junkankitou [Seisaku]-Ippan-001; H29–Junkankitou–Ippan–003 and 20FA1002

OnBehalf

EPOCH-JAPAN

Introduction

Absolute risk of Lifetime risk (LTR) is useful estimate for risk communication compared with short term risk or relative risk especially for young people. Proteinuria is leading cause of end-stage kidney disease (ESKD) and independent risk factor for cardiovascular disease (CVD). Although nonproteinuric renal disease is global burden of ESKD, it has been poorly focused. To date, there have been no reports of impact of proteinuria and low eGFR on LTR with the outcome of CVD death in Asian population.

Purpose

We aimed to estimate LTR of CVD death stratified by the status of proteinuria and low eGFR.

Methods

We used modified Kaplan-Meier approach to estimate the remaining lifetime risk of cardiovascular death based on EPOCH-JAPAN(Evidence for Cardiovascular Prevention From Observational Cohorts in Japan) database. LTR was estimated at each index age starting from 40 years for those with proteinuria and without proteinuria stratified by low eGFR, which is defined as eGFR &lt;60 ml/min/1.73 m². Participants were classified into three groups, which were those with proteinuria (Proteinuria (+)), those without proteinuria with low eGFR (Proteinuria (-)/Low eGFR (+)), those without proteinuria without low eGFR (Proteinuria (-)/Low eGFR (-)).

Results

A total of 47,292 participants from 9 cohorts was included in the analysis. Mean follow-up period was 14.6 years with 690,463 person years and total CVD death was 1,075 in men and 1,193 in women. The LTRs at the index age of 40 years were as follows: 17.7% (95% confidence interval: 15.4 – 19.0%) in Proteinuria (-)/Low eGFR (-) group, 26.2% (20.2 – 31.1%) in Proteinuria (-)/low eGFR (+) group, 24.5% (15.1 – 29.3%) in Proteinuria (+) group for men; 15.3%(13.7 – 16.5%), 29.9%(14.7 – 46.8%) , 28.3%(19.4 – 34.7%) for women.

Conclusions

We observed that those without proteinuria with low eGFR have equivalently high LTR with those with proteinuria. These results indicate that even in the absence of proteinuria, low eGFR has high impact on LTR. Lifestyle modification from young age is necessary to prevent from renal dysfunction.

Synaptic Effect of Aδ-Fibers by Pulse-Train Electrical Stimulation

Electrical stimulation of specific small fibers (Aδ- and C-fibers) is used in basic studies on nociception and neuropathic pain and to diagnose neuropathies. For selective stimulation of small fibers, the optimal stimulation waveform parameters are an important aspect together with the study of electrode design. However, determining an optimal stimulation condition is challenging, as it requires the characterization of the response of the small fibers to electrical stimulation. The perception thresholds are generally characterized using single-pulse stimulation based on the strength-duration curve. However, this does not account for the temporal effects of the different waveforms used in practical applications. In this study, we designed an experiment to characterize the effects of multiple pulse stimulation and proposed a computational model that considers electrostimulation of fibers and synaptic effects in a multiscale model. The measurements of perception thresholds showed that the pulse dependency of the threshold was an exponential decay with a maximum reduction of 55%. In addition, the frequency dependence of the threshold showed a U-shaped response with a reduction of 25% at 30 Hz. Moreover, the computational model explained the synaptic effects, which were also confirmed by evoked potential recordings. This study further characterized the activation of small fibers and clarified the synaptic effects, demonstrating the importance of waveform selection.

Human exposure to radiofrequency energy above 6 GHz: review of computational dosimetry studies

International guidelines/standards for human protection from electromagnetic fields have been revised recently, especially for frequencies above 6 GHz where new wireless communication systems have been deployed. Above this frequency a new physical quantity 'absorbed/epithelial power density' has been adopted as a dose metric. Then, the permissible level of external field strength/power density is derived for practical assessment. In addition, a new physical quantity, fluence or absorbed energy density, is introduced for protection from brief pulses (especially for shorter than 10 s). These limits were explicitly designed to avoid excessive increases in tissue temperature, based on electromagnetic and thermal modeling studies but supported by experimental data where available. This paper reviews the studies on the computational modeling/dosimetry which are related to the revision of the guidelines/standards. The comparisons with experimental data as well as an analytic solution are also been presented. Future research needs and additional comments on the revision will also be mentioned.

Influence of segmentation accuracy in structural MR head scans on electric field computation for TMS and tES

In several diagnosis and therapy procedures based on electrostimulation effect, the internal physical quantity related to the stimulation is the induced electric field. To estimate the induced electric field in an individual human model, the segmentation of anatomical imaging, such as magnetic resonance image (MRI) scans, of the corresponding body parts into tissues is required. Then, electrical properties associated with different annotated tissues are assigned to the digital model to generate a volume conductor. However, the segmentation of different tissues is a tedious task with several associated challenges specially with tissues appear in limited regions and/or low-contrast in anatomical images. An open question is how segmentation accuracy of different tissues would influence the distribution of the induced electric field. In this study, we applied parametric segmentation of different tissues to exploit the segmentation of available MRI to generate different quality of head models using deep learning neural network architecture, named ForkNet. Then, the induced electric field are compared to assess the effect of model segmentation variations. Computational results indicate that the influence of segmentation error is tissue-dependent. In brain, sensitivity to segmentation accuracy is relatively high in cerebrospinal fluid (CSF), moderate in gray matter (GM) and low in white matter for transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES). A CSF segmentation accuracy reduction of 10% in terms of Dice coefficient (DC) lead to decrease up to 4% in normalized induced electric field in both applications. However, a GM segmentation accuracy reduction of 5.6% DC leads to increase of normalized induced electric field up to 6%. Opposite trend of electric field variation was found between CSF and GM for both TMS and tES. The finding obtained here would be useful to quantify potential uncertainty of computational results.

Dosimetry Analysis in Non-brain Tissues During TMS Exposure of Broca's and M1 Areas

For human protection, the internal electric field is used as a dosimetric quantity for electromagnetic fields lower than 5–10 MHz. According to international standards, in this frequency range, electrostimulation is the main adverse effect against which protection is needed. One of the topics to be investigated is the quantification of the internal electric field threshold levels of perception and pain. Pain has been reported as a side effect during transcranial magnetic stimulation (TMS), especially during stimulation of the Broca’s (speech) area of the brain. In this study, we designed an experiment to conduct a dosimetry analysis to quantify the internal electric field corresponding to perception and pain thresholds when targeting the Broca’s and M1 areas from magnetic stimulator exposure. Dosimetry analysis was conducted using a multi-scale analysis in an individualized head model to investigate electrostimulation in an axonal model. The main finding is that the stimulation on the primary motor cortex has higher perception and pain thresholds when compared to Broca’s area. Also, TMS-induced electric field applied to Broca’s area exhibited dependence on the coil orientation at lower electric field threshold which was found to be related to the location and thickness of pain fibers. The derived dosimetry quantities provide a scientific rationale for the development of human protection guidelines and the estimation of possible side effects of magnetic stimulation in clinical applications.

Electrical Characterisation of Aδ-Fibres Based on Human in vivo Electrostimulation Threshold

Electrical stimulation of small fibres is gaining attention in the diagnosis of peripheral neuropathies, such as diabetes mellitus, and pain research. However, it is still challenging to characterise the electrical characteristics of axons in small fibres (Aδ and C fibres). In particular, in vitro measurement for human Aδ-fibre is difficult due to the presence of myelin and ethical reason. In this study, we investigate the in vivo electrical characteristics of the human Aδ-fibre to derive strength-duration (S-D) curves from the measurement. The Aδ-fibres are stimulated using coaxial planar electrodes with intraepidermal needle tip. For human volunteer experiments, the S-D curve of Aδ-fibre is obtained in terms of injected electrical current. With the computational analysis, the standard deviation of the S-D curve is mostly attributed to the thickness of the stratum corneum and depth of the needle tip, in addition to the fibre thickness. Then, we derive electrical parameters of the axon in the Aδ-fibre based on a conventional fibre model. The parameters derived here would be important in exploring the optimal stimulation condition of Aδ-fibres.

Effect of a Lens Protein in Low-Temperature Culture of Novel Immortalized Human Lens Epithelial Cells (iHLEC-NY2)

The prevalence of nuclear cataracts was observed to be significantly higher among residents of tropical and subtropical regions compared to those of temperate and subarctic regions. We hypothesized that elevated environmental temperatures may pose a risk of nuclear cataract development. The results of our in silico simulation revealed that in temperate and tropical regions, the human lens temperature ranges from 35.0 °C to 37.5 °C depending on the environmental temperature. The medium temperature changes during the replacement regularly in the cell culture experiment were carefully monitored using a sensor connected to a thermometer and showed a decrease of 1.9 °C, 3.0 °C, 1.7 °C, and 0.1 °C, after 5 min when setting the temperature of the heat plate device at 35.0 °C, 37.5 °C, 40.0 °C, and 42.5 °C, respectively. In the newly created immortalized human lens epithelial cell line clone NY2 (iHLEC-NY2), the amounts of RNA synthesis of αA crystallin, protein expression, and amyloid β (Aβ)1-40 secreted into the medium were increased at the culture temperature of 37.5 °C compared to 35.0 °C. In short-term culture experiments, the secretion of Aβ1-40 observed in cataracts was increased at 37.5 °C compared to 35.0 °C, suggesting that the long-term exposure to a high-temperature environment may increase the risk of cataracts.