Anatomical Human Model Research Articles

Eccrine sweat glands associate with the human hair follicle within a defined compartment of dermal white adipose tissue.

Eccrine sweat glands (ESGs) are critical for thermoregulation and are involved in wound healing. ESGs have traditionally been considered as separate skin appendages without connection to the pilosebaceous unit (PSU). However, recent preliminary evidence has encouraged the hypothesis that the PSU and ESG are more interconnected than previously thought. To re-evaluate the morphology of human skin adnexa with an integrated three-dimensional (3D) perspective in order to explore the possible interconnections that the PSU and the ESG may form. A systematic 3D reconstruction method of skin sections, direct visualization of human scalp follicular unit transplant grafts and a scalp strip ex vivo were used to validate and further explore the hypothesis. We demonstrate that the coiled portion of most ESGs is morphologically integrated into the PSU of human scalp skin and forms a structural unit that is embedded into a specific, hair follicle-associated region of dermal white adipose tissue (dWAT). This newly recognized unit is easily accessible and experimentally tractable by organ culture of follicular units and can be visualized intravitally. We propose a model of functional human skin anatomy in which ESGs are closely associated with the PSU and the dWAT to form a common homeostatic tissue environment, which may best be encapsulated in the term 'adnexal skin unit'. The challenge now is to dissect how each component of this superstructure of human skin functionally cooperates with and influences the other under physiological conditions, during regeneration and repair and in selected skin diseases.

EVALUATING EXTREMELY LOW FREQUENCY MAGNETIC FIELDS IN THE REAR SEATS OF THE ELECTRIC VEHICLES.

In the electric vehicles (EVs), children can sit on a safety seat installed in the rear seats. Owing to their smaller physical dimensions, their heads, generally, are closer to the underfloor electrical systems where the magnetic field (MF) exposure is the greatest. In this study, the magnetic flux density (B) was measured in the rear seats of 10 different EVs, for different driving sessions. We used the measurement results from different heights corresponding to the locations of the heads of an adult and an infant to calculate the induced electric field (E-field) strength using anatomical human models. The results revealed that measured B fields in the rear seats were far below the reference levels by the International Commission on Non-Ionizing Radiation Protection. Although small children may be exposed to higher MF strength, induced E-field strengths were much lower than that of adults due to their particular physical dimensions.

High-Frequency Electromagnetic Field Analysis by COCR Method Using Anatomical Human Body Models

The authors investigate a high-accuracy analysis technique for the electromagnetic field in a human body by using the parallel finite-element method. In the high-frequency electromagnetic field analysis with anatomical human models, speed-up of calculation is one of the most important topics. In this paper, we implement the code and evaluate the performance of two kinds of iterative method for the interface problem in the domain decomposition method (DDM) by numerical experiments using large-scale human body models. As the results, the conjugate orthogonal conjugate residual method is very effective as the interface solver in the DDM method for the high-frequency electromagnetic field analysis using the anatomical human model.

Non-Uniform Magnetic Field Exposure Assessment Using Coupling Factors Based on 3-D Anatomical Human Model

Coupling factors are calculated in order to facilitate non-uniform magnetic field exposure assessment. Coupling factors take into account the characteristics of a localized non-uniform field source, whereas reference levels in electromagnetic field safety guidelines only consider uniform field exposures. The calculations are performed using several different equivalent human models including simplified homogeneous models and a complex anatomical model. Three types of non-uniform sources are considered; a circular coil in a vertical plane, a circular coil in a horizontal plane, and a straight wire in a horizontal plane. For modeling and quasi-static electromagnetic simulation of the complex anatomical human model, Sim4Life software was used, which applies finite-element method to graded voxel meshes. The dependence of coupling factor values on the various parameters including source type, distance between source and human model, coil radius, and type of the equivalent human model used is analyzed. Also, separate definitions of coupling factors given in various IEC standards are analyzed and their differences in practical applications are investigated.

Temperature elevation in the human brain and skin with thermoregulation during exposure to RF energy

BackgroundTwo international guidelines/standards for human protection from electromagnetic fields define the specific absorption rate (SAR) averaged over 10 g of tissue as a metric for protection against localized radio frequency field exposure due to portable devices operating below 3–10 GHz. Temperature elevation is suggested to be a dominant effect for exposure at frequencies higher than 100 kHz. No previous studies have evaluated temperature elevation in the human head for local exposure considering thermoregulation. This study aims to discuss the temperature elevation in a human head model considering vasodilation, to discuss the conservativeness of the current limit.MethodsThis study computes the temperature elevations in an anatomical human head model exposed to radiation from a dipole antenna and truncated plane waves at 300 MHz–10GHz. The SARs in the human model are first computed using a finite-difference time-domain method. The temperature elevation is calculated by solving the bioheat transfer equation by considering the thermoregulation that simulates the vasodilation.ResultsThe maximum temperature elevation in the brain appeared around its periphery. At exposures with higher intensity, the temperature elevation became larger and reached around 40 °C at the peak SAR of 100 W/kg, and became lower at higher frequencies. The temperature elevation in the brain at the current limit of 10 W/kg is at most 0.93 °C. The effect of vasodilation became notable for tissue temperature elevations higher than 1–2 °C and for an SAR of 10 W/kg. The temperature at the periphery was below the basal brain temperature (37 °C).ConclusionsThe temperature elevation under the current guideline for occupational exposure is within the ranges of brain temperature variability for environmental changes in daily life. The effect of vasodilation is significant, especially at higher frequencies where skin temperature elevation is dominant.

Relationship of External Field Strength With Local and Whole-Body Averaged Specific Absorption Rates in Anatomical Human Models

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines and the IEEE C95.1 standard are currently under revision. In the guidelines/standard, the dominant effect for electromagnetic field exposures at frequencies above 100 kHz is the thermal effect. The whole-body-and 10g-averaged specific absorption rates (SARs), which are surrogates for core and local temperature elevations, respectively, are set as metrics for exposure evaluation. The external field strengths or incident power density, corresponding to the limit for SARs, are also used as metrics for practical compliance purposes. Although the limits for the SARs are identical amongst the guidelines/standard, the limits for the external field strengths differ by a factor of 7.4–12.9 in an intermediate frequency range (100 kHz–100 MHz). Due to the fact that the standard/guidelines were published before the computation with anatomical human models was available, it is worth revisiting the relationship between the SARs and external field strengths by computations using the human models. Intercomparison using different numerical codes was also performed to verify the results. For the main finding, as expected, the 10g-averaged SAR was a less restrictive factor for whole-body exposure over the frequencies considered in this paper. It was also found that the relationship between SARs and external field strength was satisfied, but was more conservative in the ICNIRP guidelines, whereas there were slight discrepancies below 30 MHz in the IEEE standard. The computational results would be useful for revising the permissible external field strength based on scientific results.

Intercomparison of In Situ Electric Fields in Human Models Exposed to Spatially Uniform Magnetic Fields

IEEE C95.1 (radio frequency) and C95.6 (low frequency) standards for human protection from electromagnetic fields are currently under revision. In the next revision, they will be combined into one standard covering the frequency range from 0 Hz to 300 GHz. Although the C95.1 standard considers anatomical human models for deriving the relationship between internal and external field strengths, homogeneous ellipses are used in the C95.6 standard. In the guidelines of the International Commission on Non-Ionizing Radiation Protection, anatomical human models are used together with reduction factors to account for numerical uncertainty. It is worth revisiting their relationship when using different anatomical models. In this paper, five research groups performed a comparative study to update the state-of-the-art knowledge of in situ electric fields in anatomical human models when exposed to uniform low-frequency magnetic fields. The main goals were to clarify both numerical uncertainty and model variability. The computational results suggest a high consistency among in situ field strengths across laboratories; agreement in the 99th percentile with a discrepancy of under 5% was achieved. The in situ electric fields varied as expected given the models’ different dimensions. The induction factor, which is the ratio of the in situ electric fields for the temporal derivative of the external magnetic flux density, is derived for body parts and tissues. The classification of body parts into “the limb” and “other tissues” is shown to be critical for determining the in situ field strength.

Temperature Rise for Brief Radio-Frequency Exposure Below 6 GHz

In international guidelines for human protection from radio-frequency (RF) electromagnetic fields, the specific absorption rate (SAR) averaged over 6 min and 10 g of tissue is used as a physical quantity to prevent excess local temperature rise. The resultant SAR restriction has been set to avoid potential adverse health effects due to the temperature elevation resulting from RF energy absorption. In the public consultation version of the upcoming ICNIRP RF guidelines (July 10, 2018), a specific absorption (SA) limit was set to avoid heating from brief exposures (shorter than 6 min). However, to the best of our knowledge, no prior research has evaluated the temperature rise for single/multiple pulses with energy equivalent to the 6-min exposure SAR restriction for continuous waves. This paper computed the temperature rise for brief pulse exposures based on bioheat computations. We first confirmed that the peak temperature rise for a pulse with SA corresponding to occupational exposure exceeds the steady-state temperature rise for temporally uniform continuous wave exposure. We then proposed the SA limit from a regression curve that is dependent on the duration of brief exposure to RF pulse(s). The temperature rise in a multilayer cube and an anatomical human model were also computed for exposures to multiple pulses. The temperature rise from multiple pulses satisfying the formula was found to be below the relevant threshold level. The SA based on this regression curve can be used as a metric to prevent excess temperature rise for different brief exposure scenarios below 6 min.

Modelling of the Current Density Distributions during Cortical Electric Stimulation for Neuropathic Pain Treatment.

In the last two decades, motor cortex stimulation has been recognized as a valuable alternative to pharmacological therapy for the treatment of neuropathic pain. Although this technique started to be used in clinical studies, the debate about the optimal settings that enhance its effectiveness without inducing tissue damage is still open. To this purpose, computational approaches applied to realistic human models aimed to assess the current density distribution within the cortex can be a powerful tool to provide a basic understanding of that technique and could help the design of clinical experimental protocols. This study aims to evaluate, by computational techniques, the current density distributions induced in the brain by a realistic electrode array for cortical stimulation. The simulation outcomes, summarized by specific metrics quantifying the efficacy of the stimulation (i.e., the effective volume and the effective depth of penetration) over two cortical targets, were evaluated by varying the interelectrode distance, the stimulus characteristics (amplitude and frequency), and the anatomical human model. The results suggest that all these parameters somehow affect the current density distributions and have to be therefore taken into account during the planning of effective electrical cortical stimulation strategies. In particular, our calculations show that (1) the most effective interelectrode distance equals 2 cm; (2) increasing voltage amplitudes increases the effective volume; (3) increasing frequencies allow enlarging the effective volume; and (4) the effective depth of penetration is strictly linked to both the anatomy of the subject and the electrode placement.

Risk Management of Heatstroke Based on Fast Computation of Temperature and Water Loss Using Weather Data for Exposure to Ambient Heat and Solar Radiation

Several indexes, such as the heat index, wet-bulb globe temperature, and the universal thermal climate index, are used to estimate the risk of seasonal heat illness. These indexes correspond to the heat load of an individual in identical environmental conditions for a prolonged period of time. In daily life, the environment changes with time, and different individuals are vulnerable to heat-related illness to different degrees. An appropriate health risk assessment covering 90% of the population would facilitate an effective response to increased rates of heat illness for major summer sport events and the elderly in daily life. In this paper, a fast computation for simulating temperature elevation and sweating is implemented using weather forecast data. In particular, a bioheat equation considering thermoregulatory responses is solved in the time domain using anatomical human body models including young adults, the elderly, and children. To accelerate simulation, the computational code is vectorized and parallelized, and subsequently implemented on an SX-ACE supercomputer. The computational results are validated in typical cases of young adults, children, and the elderly. The computational time for estimating the body temperature elevation and water loss for 3 h based on the forecasted temperature, humidity, and solar radiation was 8 min for a total of nine human models that cover an estimated 90% of the population. This demonstrates the effectiveness of the proposed system for pre-emptive health risk management. To improve public awareness, a web-based risk management application has been developed and used, since 2017 in Japan.

Model-based Vestibular Afferent Stimulation: Modular Workflow for Analyzing Stimulation Scenarios in Patient Specific and Statistical Vestibular Anatomy.

Our sense of balance and spatial orientation strongly depends on the correct functionality of our vestibular system. Vestibular dysfunction can lead to blurred vision and impaired balance and spatial orientation, causing a significant decrease in quality of life. Recent studies have shown that vestibular implants offer a possible treatment for patients with vestibular dysfunction. The close proximity of the vestibular nerve bundles, the facial nerve and the cochlear nerve poses a major challenge to targeted stimulation of the vestibular system. Modeling the electrical stimulation of the vestibular system allows for an efficient analysis of stimulation scenarios previous to time and cost intensive in vivo experiments. Current models are based on animal data or CAD models of human anatomy. In this work, a (semi-)automatic modular workflow is presented for the stepwise transformation of segmented vestibular anatomy data of human vestibular specimens to an electrical model and subsequently analyzed. The steps of this workflow include (i) the transformation of labeled datasets to a tetrahedra mesh, (ii) nerve fiber anisotropy and fiber computation as a basis for neuron models, (iii) inclusion of arbitrary electrode designs, (iv) simulation of quasistationary potential distributions, and (v) analysis of stimulus waveforms on the stimulation outcome. Results obtained by the workflow based on human datasets and the average shape of a statistical model revealed a high qualitative agreement and a quantitatively comparable range compared to data from literature, respectively. Based on our workflow, a detailed analysis of intra- and extra-labyrinthine electrode configurations with various stimulation waveforms and electrode designs can be performed on patient specific anatomy, making this framework a valuable tool for current optimization questions concerning vestibular implants in humans.

Transcranial Magnetic Stimulation: A New Coil Form for Deep Brain Stimulation

Transcranial magnetic stimulation (TMS) can be used to excite the human cortex noninvasively as well as activates scalp muscles and sensory receptors. Since the field of the old traditional coils drops off quickly as it goes into the brain, a deep brain stimulation overstimulates the surface which is not only painful but also causes more effects on the outer part of the brain with little inside stimulation. This paper presents a Magneto Quasi-Static (Biot-Savart) approximation, used with the assistance of a low-frequency solver, to simulate the TMS application and finds the electric and magnetic fields distribution on an anatomical human head model due to the exposure from the applied pulse signal, of 10000 A peak and 280 µs width, through different coil forms. A well-known traditional coil was examined as well as a novel coil form was suggested and simulated to examine deep brain stimulation.

Improvement of Electromagnetic Field Distributions Using High Dielectric Constant (HDC) Materials for CTL-Spine MRI: Numerical Simulations and Experiments.

This study investigates the use of pads with high dielectric constant (HDC) materials to alter electromagnetic field distributions in patients during magnetic resonance imaging (MRI). The study was performed with numerical simulations and phantom measurements. An initial proof-of-concept and validation was performed using a phantom at 64 MHz, showing increases of up to 10% in electromagnetic field when using distilled water as the high dielectric material. Additionally, numerical simulations with computational models of human anatomy were performed at 128 MHz. Results of these simulations using barium titanate (BaTiO3) beads showed a 61% increase of [Formula: see text] with a quadrature driven RF coil and a 64% increase with a dual-transmit array. The presence of the HDC material also allowed for a decrease of SAR up to twofold (e.g., peak 10 g-averaged SAR from 54 to 22 W/kg with a quadrature driven RF coil and from 27 to 22 W/kg with a dual-transmit array using CaTiO3 powder at 128 MHz). The results of this study show that the use of HDC pads at 128 MHz for MRI spine applications could result in improved magnetic fields within the region of interest, while decreasing SAR outside the region.

A Co-Simulation Scalar-Potential Finite Difference Method for the Numerical Analysis of Human Exposure to Magneto-Quasi-Static Fields

A two-step approach for the simulation of the exposure of a human body to magneto-quasi-static fields is presented. The co-simulation scalar-potential finite difference method is a calculation scheme, where a distribution of the magnetic vector potential inside the biological tissues is derived from a free space magnetic source field simulation using a tree-cotree gauging algorithm. With the obtained magnetic vector potential, the electric field strength inside the voxel representation of the biological tissues is calculated solving a high-dimensional discrete Poisson equation on a high-performance workstation with multiple graphics processing units (GPUs). An exposure scenario, including an inductive power transfer system, a car model, and an anatomical human body voxel model, is simulated using this approach, and the results are compared with a monolithic scaled-frequency finite difference time domain simulation. The maximum body-internal electric field strength (voxel average) is determined and compared with basic restrictions recommended by the International Commission on Non-Ionizing Radiation Protection.

Derivation of Coupling Factors for Different Wireless Power Transfer Systems: Inter- and Intralaboratory Comparison

In this study, the inter- and intralaboratory comparison of coupling factors is discussed for human exposure to nonuniform magnetic field from different wireless power transfer (WPT) systems. In order to derive the coupling factors, different laboratories computed the internal electric field and specific absorption rate (SAR) for different WPT configurations. The concept of coupling factors was originally introduced in the International Electrotechnical Commission (IEC) 62311 and 62233 standards, for product safety assessment. For WPT systems, extension of the coupling factors is discussed in the IEC working group. This factor enables the estimation of the internal electric field and the SAR without detailed computation using human anatomical models. The coupling factors were computed for different WPT systems, such as an electric vehicle charging at approximately 100 kHz, induction coupling systems (140 kHz band), and home appliances (6.78 MHz). Four in-house codes were used in this inter- and intralaboratory comparison study to compute the coupling factors for the systems. Similar tendencies were observed in the coupling factors obtained by the groups. The difference between the coupling factors of different research groups is 30% when considering the same exposure scenarios. The coupling factors for different WPT systems are different because of the frequency, coil size, and existence of the magnetic sheet (shield). The variability of the internal electric field for WPT systems is also investigated to set the coupling factor required for practical use.

Computational Dosimetry of the Human Head Exposed to Near-Field Microwaves Using Measured Blood Flow

Computational human thermal modeling studies have suffered from lack of reliable data regarding tissue blood flow. In this study, we report the measured results of blood flow on the surface of the head at multiple sites in human subjects (12 healthy young male subjects, 22-24 years), using a laser Doppler blood-flow method. We then incorporate these measured blood flow in a computational bioheat thermal model in anatomical human head models and investigate the effects of individual variations in blood flow on a microwave-induced temperature elevation in the frequency range from 1 to 12 GHz. The measurements show variations in blood flow at different sites and depths from the skin surface. However, computational bioheat modeling indicates that the typical variability of peak temperature elevation in the head due to individual and regional variations in the blood flow is less than ±15%. The presented data will aid in the development of more accurate and consistent human thermal models and strengthen the thermophysiological rationale of guidelines and standards for human radio-frequency near-field exposure.

Learning Approaches in Gross Anatomy among Physical Therapy Students: A Comparative Study

Anatomy is a foundation subject in the health professions curriculum. Learning human anatomy is an integral component of physical therapy education and professional practice. The physical therapy curriculum in the Philippines requires dissection of the human cadaver as the primary mode of instruction during laboratory sessions. With the advancement of technology, human anatomical models, and video presentations are now readily available for the students to use. However, consensus regarding the best learning approach to anatomy remains obscure, and the prerogative of availing all these resources in anatomy will impact on the school as well as on the students. This study aimed to compare the learning approaches in gross anatomy among physical therapy students. It utilized a comparative experimental method among 40 third year physical therapy students. Four (4) sets of 50 points labeling items administered immediately after every session serve as their post-tests. It is concluded that physical therapy students can learn knowledge in gross anatomy regardless of learning approach employed. Using textbook approach for independent study is comparable to the use of alternative learning approaches such as using cadaver dissection, video presentation, and anatomical model when students learn gross anatomy. Gaining knowledge in gross anatomy will be enhanced when textbook approach is combined with either video presentation or anatomical model approach. However, the use of human cadaver dissection does not compliment with textbook approach to enhance learning gross anatomy. Keywords : learning approaches, gross anatomy, physical therapy, dissection, textbook approach, video presentation, anatomical model.

Design Methodology of a Printed WPT System for HF-Band Mid-Range Applications Considering Human Safety Regulations

A methodology for the design of printed magnetically coupled resonant wireless power-transfer (WPT) systems is proposed. The design methodology aims at a well-matched system with a maximized power-transfer efficiency for mid-range applications. The system consists of two identical resonant coils driven by high-quality factor loops. The proposed design criteria allows obtaining maximum achievable transfer efficiency and impedance matching at any defined distance without any external matching circuits connected to the driven loops. For validation purposes, a printed WPT system at 10 MHz is fabricated targeting 1-m distance between the transmitting and receiving sides. Its performances in terms of reflection and transmission coefficients, as well as in terms of generated electric and magnetic fields, have been characterized numerically and experimentally. The impact of human body presence on the system has also been investigated observing the splitting in two frequencies of the common resonant frequency of the coils. A dosimetric study has been conducted using a detailed high-resolution anatomical human body model and considering E 99 , J 1 cm 2 , and specific absorption rate (SAR) (local and whole body averaged SAR) as exposure metrics. It has been observed that peak exposure levels appear in different tissues depending on the body location. Compliance with the international commission on nonionizing radiation protection (ICNIRP) reference level as well as basic restrictions has been studied followed by computing the maximum allowable input power. It has been found that, with the body located 1 m away from the transmitting coil, the maximum allowable input power satisfying E 99 is in the order of MW, whereas it reduces to tens of kilowatt when considering SAR and J1 cm 2 . The latter has been noticed to be the most restrictive dosimetric quantity.

Forces distribution during plantar stand among the myo-osteo-joint components of the foot. Simulations and analysis on a human anatomical network model

The anatomical network analysis allows to explore the network of relationships among the anatomical parts of the human body. In our previous work the features of (2) a wide anatomical - biomechanical network were investigated. The human foot represents a highly complex anatomical structure that carries motor-sensor functions and load distribution through a network of bones, muscles, joints and tendons. The main contacts with the ground during standing position match the metatarsal region for the forefoot and the calcaneus for the backfoot. Studies on the transmission of load in the forefoot area have shown that the latter cannot be considered as a metatarsal arch but rather as a continuous line in physiological condition of metatarsal motility (1, 3). Moreover, electromyographic studies (4, 5, 6) can only give information on the activation of the extrinsic muscles of the foot during walking, without providing any response about the distribution of the load, and the different role played by the numerous anatomical structures involved (7). Here we present a weighted anatomical network of the foot, where every single node has a numerical value deriving from both the Young’s modulus calculation and the number of connections with other nodes. The network consists of 116 nodes interconnected by 219 links and represents the biomechanical structure of the foot as activated by the plantar support. By the collection of the data, the nodes cluster of the foot can be extrapolated and by detecting of the direct pressure on the plantar support, the virtual foot network can be reconstructed.

Human ventricular activation sequence and the simulation of the electrocardiographic QRS complex and its variability in healthy and intraventricular block conditions.

AimsTo investigate how variability in activation sequence and passive conduction properties translates into clinical variability in QRS biomarkers, and gain novel physiological knowledge on the information contained in the human QRS complex.Methods and resultsMultiscale bidomain simulations using a detailed heart-torso human anatomical model are performed to investigate the impact of activation sequence characteristics on clinical QRS biomarkers. Activation sequences are built and validated against experimentally-derived ex vivo and in vivo human activation data. R-peak amplitude exhibits the largest variability in terms of QRS morphology, due to its simultaneous modulation by activation sequence speed, myocardial intracellular and extracellular conductivities, and propagation through the human torso. QRS width, however, is regulated by endocardial activation speed and intracellular myocardial conductivities, whereas QR intervals are only affected by the endocardial activation profile. Variability in the apico-basal location of activation sites on the anterior and posterior left ventricular wall is associated with S-wave progression in limb and precordial leads, respectively, and occasional notched QRS complexes in precordial derivations. Variability in the number of early activation sites successfully reproduces pathological abnormalities of the human conduction system in the QRS complex.ConclusionVariability in activation sequence and passive conduction properties captures and explains a large part of the clinical variability observed in the human QRS complex. Our physiological insights allow for a deeper interpretation of human QRS biomarkers in terms of QRS morphology and location of early endocardial activation sites. This might be used to attain a better patient-specific knowledge of activation sequence from routine body-surface electrocardiograms.