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To theoretically investigate the feasibility of a novel procedure for testing the MRI gradient-induced heating of medical devices and translating the results into clinical practice.The concept of index of stress is introduced by decoupling the time waveform characteristics of the gradient field signals from the field spatial distribution within an MRI scanner. This index is also extended to consider the anisotropy of complex bulky metallic implants. Merits and drawbacks of the proposed index of stress are investigated through virtual experiments. In particular, the values of the index of stress evaluated for realistic orthopedic implants placed within an ASTM phantom are compared with accurate heating simulations performed with 2 anatomic body models (a man and a woman) implanted through a virtual surgery procedure.The manipulation of the proposed index of stress allows to identify regions within the MRI bore where the implant could affect the safety of the examinations. Furthermore, the conducted analysis shows that the power dissipated into the implant by the induced eddy currents is a dosimetric quantity that estimates well the maximum temperature increase in the tissues surrounding the implant.The results support the adoption of an anisotropic index of stress to regulate the gradient-induced heating of geometrically complex implants. They also pave the way for a laboratory characterization of the implants based on electrical measurements, rather than on thermal measurements. The next step will be to set up a standardized experimental procedure to evaluate the index of stress associated with an implant.

Military hardware and technology transfer is increasingly becoming a crucial factor in international relations. This is especially so when the military hardware transfer involves sophisticated weap...

Purpose To investigate how the simultaneous exposure to gradient and RF fields affects the temperature rise in patients with a metallic hip prosthesis during an MRI session. Methods In silico analysis was performed with an anatomically realistic human model with CoCrMo hip implant in 12 imaging positions. The analysis was performed at 1.5 T and 3 T, considering four clinical sequences: turbo spin-echo, EPI, gradient-echo, and true fast imaging sequence with steady precession. The exposure to gradient and RF fields was evaluated separately and superposed, by adopting an ad hoc computational algorithm. Temperature increase within the body, rather than specific absorption rate, was used as a safety metric. Results With the exception of gradient-echo, all investigated sequences produced temperature increases higher than 1 K after 360 seconds, at least for one body position. In general, RF-induced heating dominates the turbo spin-echo sequence, whereas gradient-induced heating prevails with EPI; the situation with fast imaging sequence with steady precession is more diversified. The RF effects are enhanced when the implant is within the RF coil, whereas the effects of gradient fields are maximized if the prosthesis is outside the imaging region. Cases for which temperature-increase thresholds were exceeded were identified, together with the corresponding amount of tissue mass involved and the exposure time needed to reach these limits. Conclusion The analysis confirms that risky situations may occur when a patient carrying a hip implant undergoes an MRI exam and that, in some cases, the gradient field heating may be significant. In general, exclusion criteria only based on whole-body specific absorption rate may not be sufficient to ensure patients' safety.

Objective. To quantify the effects of different levels of realism in the description of the anatomy around hip, knee or shoulder implants when simulating, numerically, radiofrequency and gradient-induced heating in magnetic resonance imaging. This quantification is needed to define how precise the digital human model modified with the implant should be to get realistic dosimetric assessments. Approach. The analysis is based on a large number of numerical simulations where four ‘levels of realism’ have been adopted in modelling human bodies carrying orthopaedic implants. Main results. Results show that the quantification of the heating due to switched gradient fields does not strictly require a detailed local anatomical description when preparing the digital human model carrying an implant. In this case, a simple overlapping of the implant CAD with the body anatomy is sufficient to provide a quite good and conservative estimation of the heating. On the contrary, the evaluation of the electromagnetic field distribution and heating caused by the radiofrequency field requires an accurate description of the tissues around the prosthesis. Significance. The results of this paper provide hints for selecting the ‘level of realism’ in the definition of the anatomical models with embedded passive implants when performing simulations that should reproduce, as closely as possible, the in vivo scenarios of patients carrying orthopaedic implants.

In this article, we discuss numerical aspects related to the accuracy and the computational efficiency of numerical dosimetric simulations, performed in the context of human exposure to static inductive charging systems of electric vehicles. Two alternative numerical methods based on electric vector potential and electric scalar potential formulations, respectively, are here considered for the electric field computation in highly detailed anatomical human models. The results obtained by the numerical implementation of both approaches are discussed in terms of compliance assessment with ICNIRP guidelines limits for human exposure to electromagnetic fields. In particular, different strategies for smoothing localized unphysical outliers are compared, including novel techniques based on statistical considerations. The outlier removal is particularly relevant when comparison with basic restrictions is required to define the safety of electromagnetic fields exposure. The analysis demonstrates that it is not possible to derive general conclusions about the most robust method for dosimetric solutions. Nevertheless, the combined use of both formulations, together with the use of an algorithm for outliers removal based on a statistical approach, allows to determine final results to be compared with reference limits with a significant level of reliability.

The infrapatellar fat pad is an adipose tissue in the knee that facilitates the distribution of synovial fluid and absorbs impulsive actions generated through the joint. The correlation between morphological configuration and mechanical properties is analyzed by a computational approach. The microscopic anatomy of the infrapatellar fat pad is studied aiming to measure the dimension of adipose lobules and the thickness of connective septa. Results from histomorphometric investigations show that the infrapatellar fat pad is an inhomogeneous tissue, constituted by large lobules in the superficial part and smaller lobules in the deepest one. Finite element models of the infrapatellar fat pad are developed. The first model considers the inhomogeneous conformation of the infrapatellar fat pad, composed of micro- and macro-chambers, while the second model considers a homogeneous distribution of adipose lobules with similar dimensions. Computational analyses are performed considering the static standing configuration and the passive flexion–extension movement. The computational results allow us to identify the different stress and strain fields within the tissue and to appreciate the variation of the mechanical performance of the overall system considering the distribution of adipose lobules. Results show that the distribution of adipose lobules in macro- and micro-chambers allows major deformation of the infrapatellar fat pad, decreasing the stress inside the tissues.

Mechanical stimuli are fundamental in the development of organs and tissues, their growth, regeneration or disease. They influence the biochemical signals produced by the cells, and, consequently, the development and spreading of a disease. Moreover, tumour cells are usually characterized by a decrease in the cell mechanical properties that may be directly linked to their metastatic potential. Thus, recently, the experimental and computational study of cell biomechanics is facing a growing interest. Various experimental approaches have been implemented to describe the passive response of cells; however, cell variability and complex experimental procedures may affect the obtained mechanical properties. For this reason, in-silico computational models have been developed through the years, to overcome such limitations, while proposing valuable tools to understand cell mechanical behaviour. This being the case, we propose a combined continuous-tensegrity finite element (FE) model to analyse the mechanical response of a cell and its subcomponents, observing how every part contributes to the overall mechanical behaviour. We modelled both Atomic Force Microscopy (AFM) indentation and micropipette aspiration techniques, as common mechanical tests for cells and elucidated also the role of cell cytoplasm and cytoskeleton in the global cell mechanical response.

The GPU-accelerated implementations of two three-dimensional full-wave electromagnetic solvers for scattering radiofrequency problems, based on the finite element and the finite difference methods, are compared in terms of accuracy and performances, looking also at the achieved speed-up with respect to the serial CPU implementations. The finite element method shows a speed-up of about 10 for medium-size problems, whereas the acceleration rises up to 50 when the finite difference method is used. The described codes are then used to compute the specific absorption rate of a magnetic resonance imaging radiofrequency birdcage coil in a voxel-based anatomical human model.

Magnetic resonance-based electric properties tomography (EPT) is a quantitative imaging strategy based on the magnetic resonance imaging (MRI) technology that provides non-invasively an estimate of the distribution of the electric properties (EPs), conductivity σ and permittivity e, within the human body. Different methods for implementing EPT have been proposed in the literature; three of them are collected in EPTlib, an open-source, extensible C++ library, and in its terminal application. Both EPTlib and its terminal application are freely distributed through a Github repository, that can be accessed from the project website: https://eptlib.github.io .

Ski boots are known to cause vasoconstriction in the wearer’s lower limbs and, thus, cause a “cold leg” phenomenon. To address this problem, this work provides a computational framework for analysing interactions between the ski boot and the lower limb. The geometry of the lower limb was derived from magnetic resonance imaging and computed tomography techniques and anthropometric data. The geometry of the ski boot shell was obtained by means of three-dimensional computer aided design models from a manufacturer. Concerning the ski boot liner, laser scanning techniques were implemented to capture the geometry of each layer. The mechanical models of the ski boot and the lower limb were identified and validated by means of coupled experimental investigations and computational analyses. The computational models were exploited to simulate the buckling process and to investigate interaction phenomena between the boot and the lower limb. Similarly, experimental activities were performed to further analyse the buckling phenomena. The obtained computational and experimental results were compared regarding both interaction pressure and displacements between the buckle and the corresponding buckle hooks. These comparisons provided reasonable agreement (mean value of discrepancy between the model and mean experimental results in the tibial region: 20%), underlining the model’s capability to correctly interpret results from experimental measurements. Results identified the critical areas of the leg, such as the tibial region, the calcaneal region of the foot and the anterior sole, which may suffer the most due to the hydrostatic pressure and compressive strain exerted on them. The results highlight that computational methods allow investigation of the interaction phenomena between the lower leg and ski boot, potentially providing an effective framework for a more comfortable and ergonomic design of ski boots.

Metabolically engineered cyanobacteria are promising photosynthetic cell factories to produce valuable compounds in view of a bio-based industry. However, when the producer population is affected b...

In this paper the authors present the results of a dosimetric analysis related to the exposure of live-line workers to the magnetic fields generated by high voltage overhead lines and substations. The study extends the work published by Dawson et al. in 2002, considering more evolved anatomical models nowadays available, the new reference limits given by the 2013/35/EU Directive, and a new methodology, based on the intercomparison of two alternative solvers and the use of data filtering. Moreover, additional exposure scenarios are here considered with respect to the studies already available in literature. The results show that for the exposure scenario of high voltage live line works with bare hand method, in any analyzed position, the exposure limits for the tissues of the central nervous system, as well as for all other tissues, are never exceeded, despite in some cases the action levels are exceeded. For the exposure of workers in substations near 220 kV and 380 kV line trap coils exposure is compliant with the regulatory limits if the current flowing through the line trap does not exceed the value of 1000 A. Finally, for the exposure of workers in substations near cable connections, electric field values induced in the body are always lower than regulatory limits with a phase current value equal to 1600 A r.m.s.

A numerical procedure for analyzing electromagnetic (EM) fields interactions with biological tissues is presented. The proposed approach aims at drastically reducing the computational burden required by the repeated solution of large scale problems involving the interaction of the human body with EM fields, such as in the study of the time evolution of EM fields, uncertainty quantification, and inverse problems. The proposed volume integral equation (VIE), focused on low frequency applications, is a system of integral equations in terms of current density and scalar potential in the biological tissues excited by EM fields and/or electrodes connected to the human body. The proposed formulation requires the voxelization of the human body and takes advantage of the regularity of such discretization by speeding-up the computational procedure. Moreover, it exploits recent advancements in the solution of VIE by means of iterative preconditioned solvers and ad hoc parametric Model Order Reduction techniques. The efficiency of the proposed tool is demonstrated by applying it to a couple of realistic model problems: the assessment of the peripheral nerve stimulation, performed in terms of evaluation of the induced electric field, due to the gradient coils of a magnetic resonance imaging scanner during a clinical examination and the assessment of the exposure to environmental fields at 50 Hz of live-line workers with uncertain properties of the biological tissues. Thanks to the proposed method, uncertainty quantification analyses and time domain simulations are possible even for large scale problems and they can be performed on standard computers and reasonable computation time. Sample implementation of the method is made publicly available at https://github.com/UniPD-DII-ETCOMP/BioMOR .

Patients with implanted orthopaedic devices represent a growing number of subjects undergoing magnetic resonance imaging (MRI) scans each year. MRI safety labelling is required for all implants under the EU Medical Device Regulations to ensure regulatory compliance, with each device assessed through standardised testing procedures. In this paper, we employ parametric studies to assess a range of clinically relevant factors that cause tissue heating, performing simulations with both radiofrequency (RF) and gradient coil (GC) switching fields, the latter of which is often overlooked in the literature. A series of ‘worst-case’ scenarios for both types of excitation field is discussed. In the case of GC fields, large volume implants and large plate areas with the field orientated perpendicular to the plane cause the highest heating levels, along with sequences with high rates of field switching. Implant heating from RF fields is driven primarily from the ‘antenna effect’, with thin, linear implants of resonant length resulting in the highest temperature rises. In this work, we show that simplifications may be made to the field sequence and in some cases the device geometry without significantly compromising the accuracy of the simulation results, enabling the possibility for generic estimates of the implant heating for orthopaedic device manufacturers and opportunities to simplify the safety compliance process.

Uncertainty propagation in a phaseless magnetic resonance-based electric properties tomography technique is investigated using the Monte Carlo method. The studied inverse method, which recovers the electric properties distribution at radiofrequency inside a scatterer irradiated by the coils of a magnetic resonance imaging scanner, is based on the contrast source inversion technique adapted to process phaseless input data., Comment: 4 pages, 6 figures. 2019 International Conference on Electromagnetics in Advanced Applications (ICEAA)

Engineering the metabolism of photosynthetic microorganisms with the aim of converting CO2 and water, by exploiting solar energy, into end-products of commercial value is a rising interest in the biotechnology field. The producing host that carries a genetic modification not associated with competitive fitness advantage usually experiences a production burden (i.e., a metabolic burden related to product synthesis), leading to genetic instability and abortive production phenotype. The genetic instability of these engineered strains is a major hindrance to the spreading of large-scale photosynthetic cell factory processes. This genetic instability can be studied by means of evolution experiments, which are often time-consuming. In these experiments, the cell population is subjected to a long-term culturing during which the possible variation of the number of producers and of cells that lose the production traits, here defined as retro-mutants, is recorded. Here, a mathematical model that describes the dynamics of retro-mutants into a population of metabolically engineered photosynthetic microorganisms has been developed. The model has been used to simulate evolution experiments, conducted both in continuous (chemostat and turbidostat) and semi-continuous (serial batch transfer) culturing modes. These simulations allowed identifying the set of operative parameters for each cultivation mode that optimizes an evolution experiment in terms of experimental time needed to detect the arising of retro-mutants. Moreover, it has been found that in a scale of number of microbial generations only two parameters, precisely the production burden and the mutation rate, are determinant for the appearance of retro-mutants. These parameters are intrinsic features of any metabolically engineered strain and do not depend on the adopted cultivation system or on the microbial growth kinetics characteristics. This result further extends the applicability of the model also to non-photosynthetic metabolically engineered microorganisms.

The unprecedented amount of Chinese funds dedicated to the Belt and Road Initiative (BRI) and Beijing’s win-win vision of global connectivity and development is going to face a harsh reality that encompasses a wide threat spectrum. Chinese corporations just started to acknowledge that the risks associated with outbound foreign direct investments carries a higher failure rate due to intertwined factors such as: economic crises, conflict, civil unrest, assets nationalization and currency devaluation, just to name a few. In several cases, the Chinese State-Owned Enterprises’ (SOEs) infrastructural projects, macro size and breakneck implementation speed catalyze crisis in the already unstable socio-political environments. The solution to political and criminal violence’s spillovers along the BRI requests a broader involvement that also encompasses the Chinese insurance and private security sectors.

This paper compares different experimental-computational strategies for the estimation of electric fields induced in human bodies by low-frequency magnetic sources characterized by a set of magnetic field measurements. The analysis is carried out by considering three alternative procedures, which use, as the first input, the distribution of the magnetic flux density in a volume containing the studied body or on a surface surrounding the sources. The comparison is performed on a realistic model problem, related to transcranial magnetic stimulation (TMS), in which numerically simulated “virtual measurements” are employed. The comparative analysis is developed in terms of both result accuracy and robustness against noisy input due to unavoidable experimental uncertainties. It results that by performing the measurements on a surface surrounding the sources, a significant reduction of the experimental burden is found with respect to the case of volume measurements, affecting neither the accuracy nor the robustness of the procedure. In particular, when whole body electric field evaluation must be carried out, the advantage of surface measurements with respect to volume ones becomes significant. Moreover, a preferable scheme obtained as hybridization of previously proposed strategies is identified. Besides the adoption of a TMS model problem in the comparison procedure, the achieved result can be extended to any low-frequency dosimetric assessments, where the magnetic sources are difficult to model or not completely known.

The Silk Road historical legacy legitimizes China’s Belt and Road Initiative (BRI) as a pure commercial endeavour that is not related to hegemonic strategy. The overall Belt and Road footprint has already witnessed several incidents due to a lack of corporate social responsibilities (CSRs), as well as the absence of policies devoted to avoiding environmental degradation, work-related accidents and corruption. These kinds of incidents have fomented tensions that resulted in confrontation between Chinese and local workers. Today’s global insecurity, ranging from terrorist threats to hybrid conflicts led by non-state actors, demands immediate policy responses. In this respect, it is imperative to address the normative approach to regulate the scope of the private security companies (PSCs) in light of new risks and security needs.

The Belt and Road Initiative (BRI) evolving roadmap is filled by flashpoints. As China is becoming the leading world economy there is an increasing call for active participation in stabilization process and security involvement. Free riding from the US security umbrella is over. One answer is the involvement of private security providers. Since the 1990s the re-emergence of private security companies (PSCs) and the private security and military industry has been facilitated by the restructuring of the peace dividends brought by the end of the Cold War. One of the several problems related to PSCs began with the lack of an unambiguous and mutually agreed definition of what a private security firm really is. The Chinese Mainland private security market is starting now to move from an informal and fragmented setting to a more mature sector.

The Belt and Road Initiative (BRI) launched by President Xi Jinping in 2013, which is intended to promote economic development and exchanges between China and more than 60 countries, is gaining momentum. The BRI is not immune, however, to a number of important risks that in many instances are new to Chinese companies operating abroad. One oversight that must be addressed is that the BRI requires a wide range of security considerations along both the maritime and land routes. While the security problem has not gone unnoticed in Beijing, the solutions could be found elsewhere, namely in international companies that provide armed private security, special risk assessment, insurance and, perhaps most importantly, crisis mitigation.

Beijing’s economic influence in shaping international institutions is yet to be seen in the market for force. Nevertheless the Chinese insurance sector began to realize the importance of this business niche. Traditional static security, counter-terrorism as well as kidnapping for ransom are going to provide important contracts along the Belt and Road Initiative (BRI). As it happened in the US war efforts, China is learning an important lesson: the private security companies’ (PSCs) employment practices offer short-term flexibility and economic benefits but also could produce long-term negative spillovers if not properly contained. New businesses that the Chinese private security sector is looking into are related to the protection of macro-cities and the international hunt for corrupted officials, who had fled the country in an attempt to escape with the embezzled sums.

This work analyses the thermal effects produced by the time-varying magnetic fields of a Magnetic Resonance Imaging scanner in the patient's body, also considering the case of a metallic implant. The computations are performed by the successive solution of an electromagnetic field and a thermal problem. In particular, the performances of a transient thermal solver, implemented according to the Douglas-Gunn scheme, are discussed and compared with other computational procedures. An example of application is finally presented.

Contrast source inversion electric properties tomography (CSI-EPT) is a recently developed technique for the electric properties tomography that recovers the electric properties distribution starting from measurements performed by magnetic resonance imaging scanners. This method is an optimal control approach based on the contrast source inversion technique, which distinguishes itself from other electric properties tomography techniques for its capability to recover also the local specific absorption rate distribution, essential for online dosimetry. Up to now, CSI-EPT has only been described in terms of integral equations, limiting its applicability to homogeneous unbounded background. In order to extend the method to the presence of a shield in the domain—as in the recurring case of shielded radio frequency coils—a more general formulation of CSI-EPT, based on a functional viewpoint, is introduced here. Two different implementations of CSI-EPT are proposed for a 2-D transverse magnetic model problem, one dealing with an unbounded domain and one considering the presence of a perfectly conductive shield. The two implementations are applied on the same virtual measurements obtained by numerically simulating a shielded radio frequency coil. The results are compared in terms of both electric properties recovery and local specific absorption rate estimate, in order to investigate the requirement of an accurate modeling of the underlying physical problem.

Human resources management (HRM) in China requires a different approach from the ones commonly implemented in Europe or the United States. For the casual observer, what stands out are the difficulties that Chinese workers are accustomed to facing, such as overtime work, extreme working conditions due to hazardous materials, a lack of safety regulations, and an increasing unemployment rate in low technology energy-intensive industrial sectors that is casting a shadow over the near future. The Western media tends to focus on the negative consequences such as environmental and social degradation after three decades of China’s so-called ‘economic miracle’ accompanied by double-digit GDP growth. However, it is imperative to contextualize these and other related issued within the country as a whole. While China has been evolving at breakneck speed, this fast-changing process has led to China becoming the ‘world’s factory’, it was able to reinvent itself during past and current global economic and financial crisis. This chapter introduces some case studies of Italian businesses operating in China, analyzing different phases of HRM, starting from the past financial and production crises that have led to the bankruptcy of thousands of small and medium—sized companies to the most recent collapse of Chinese stock markets. The analysis will take account of the different categories of Chinese companies such as state-owned companies (SOEs), companies that operate with other companies through joint ventures and wholly foreign owned enterprises. China’s historical and cultural background and cultural information too are considered in order avoid a mere Western interpretations of phenomena and realities that need to be understood in a local context.

This paper investigates the uncertainty propagation in magnetic resonance-based electric properties tomography, a quantitative imaging technique that recovers the electric properties distribution inside a human body at the Larmor frequency. This is a needed step in order to make the quantitative results reliable for in vivo applications. To this aim, the contrast source inversion method is investigated as a promising technique and the uncertainty propagation through the corresponding model is studied by means of the Monte Carlo method. Thanks to the increased quality in the recovered electric properties, the results suggest that TEM coils for parallel transmission could be a preferable choice.