Label-free cell based impedance measurements of ZnO nanoparticles-human lung cell interaction: a comparison with MTT, NR, Trypan blue and cloning efficiency assays.

BACKGROUND: There is a huge body of literature data on ZnOnanoparticles (ZnO NPs) toxicity. However, the reported results are seen to be increasingly discrepant, and deep comprehension of the ZnO NPs behaviour in relation to the different experimental conditions is still lacking. A recent literature overview emphasizes the screening of the ZnO NPs toxicity with more than one assay, checking the experimental reproducibility also versus time, which is a key factor for the robustness of the results. In this paper we compared high-throughput real-time measurements through Electric Cell-substrate Impedance-Sensing (ECIS®) with endpoint measurements of multiple independent assays. RESULTS: ECIS-measurements were compared with traditional cytotoxicity tests such as MTT, Neutral red, Trypan blue, and cloning efficiency assays. ECIS could follow the cell behavior continuously and noninvasively for days, so that certain long-term characteristics of cell proliferation under treatment with ZnO NPs were accessible. This was particularly important in the case of pro-mitogenic activity exerted by low-dose ZnO NPs, an effect not revealed by endpoint independent assays. This result opens new worrisome questions about the potential mitogenic activity exerted by ZnO NPs, or more generally by NPs, on transformed cells. Of importance, impedance curve trends (morphology) allowed to discriminate between different cell death mechanisms (apoptosis vs autophagy) in the absence of specific reagents, as confirmed by cell structural and functional studies by high-resolution microscopy. This could be advantageous in terms of costs and time spent. ZnO NPs-exposed A549 cells showed an unusual pattern of actin and tubulin distribution which might trigger mitotic aberrations leading to genomic instability. CONCLUSIONS: ZnO NPs toxicity can be determined not only by the intrinsic NPs characteristics, but also by the external conditions like the experimental setting, and this could account for discrepant data from different assays. ECIS has the potential to recapitulate the needs required in the evaluation of nanomaterials by contributing to the reliability of cytotoxicity tests. Moreover, it can overcome some false results and discrepancies in the results obtained by endpoint measurements. Finally, we strongly recommend the comparison of cytotoxicity tests (ECIS, MTT, Trypan Blue, Cloning efficiency) with the ultrastructural cell pathology studies.

Mechanically Assisted Total Cavopulmonary Connection With an Axial Flow Pump: Computational and In Vivo Study.

A relevant number of patients undergoing total cavopulmonary connection (TCPC) experience heart failure (HF). Heart transplant is then the final option when all other treatments fail. The axial flow blood pumps are now the state of the art; however, there is little experience in low-pressure circuits, such as support of the right ventricle or even a TCPC circulation. A new T-shaped model of mechanically assisted TCPC using the "Jarvik Child 2000" axial pump, (flow rates between 1 and 3 L/m in a range of 5000-9000 rpm) was designed, simulated numerically, and then tested in animals. Eight sheep (42-45 kg) were studied: two pilot studies, four pump-supported (PS) TCPC for 3 h, and two not pump-supported (NPS) TCPC. In the PS, the axial pump was set to maintain the baseline cardiac output (CO). Pressures, CO, systemic and pulmonary vascular resistance, lactate levels, and blood gases were recorded for 3 h. Computational fluid dynamics (CFD) study allows us to set the feasible operating condition and the safety margins to minimize the venous collapse risk. In the NPS animals, a circulatory deterioration, with increasing lactate level, occurred rapidly. In the PS animals, there was a stable cardiac index of 2.7 ± 1.4 L/min/m(2), central venous pressure of 12.3 ± 1 mm Hg, and a mean pulmonary artery pressure (PAP) of 18.1 ± 6 after 3 h of support up to 9000 rpm. systemic vascular resistance (SVR), pulmonary vascular resistance (PVR), blood gasses, and arterial lactate levels remained stable to baseline values. No caval collapse occurred. A new pediatric axial flow pump provides normal CO and physiologic stability in a new T-shaped model of TCPC in sheep, in vivo. CFD and in vivo data showed that this experimental arrangement will allow us to evaluate the potential for mechanical support in patients with Fontan failure avoiding major adverse events.

Nanostructured Medical Devices: Regulatory Perspective and Current Applications.

Nanomaterials (NMs) are having a huge impact in several domains, including the fabrication of medical devices (MDs). Hence, nanostructured MDs are becoming quite common; nevertheless, the associated risks must be carefully considered in order to demonstrate safety prior to their immission on the market. The biological effect of NMs requires the consideration of methodological issues since already established methods for, e.g., cytotoxicity can be subject to a loss of accuracy in the presence of certain NMs. The need for oversight of MDs containing NMs is reflected by the European Regulation 2017/745 on MDs, which states that MDs incorporating or consisting of NMs are in class III, at highest risk, unless the NM is encapsulated or bound in such a manner that the potential for its internal exposure is low or negligible (Rule 19). This study addresses the role of NMs in medical devices, highlighting the current applications and considering the regulatory requirements of such products.

Under the Tech Umbrella: Assessing the Landscape of Telemedicine Innovations (Telemechron Study).

The expanding role of technology assessment in telemedicine is the focus of this study. An umbrella review has been proposed to delve into emerging themes within telemedicine technology assessment by scrutinizing systematic reviews gathered from PubMed and Scopus. The proposed approach was based on a standard narrative checklist and a qualification process. The selection process identified 20 systematic reviews. The main findings underscore the transformative potential of telemedicine, emphasizing technology assessments focused on systematic evaluations, stakeholder engagement, societal impact recognition, targeted interventions, and structured frameworks. While offering valuable insights, the current studies highlight certain limitations that require attention. There is a need for the following: (I) First of all, a more focused approach, primarily centered on a process-centric, multidomain, and generalizable technology assessment (TA). (II) A deeper analysis in specific healthcare areas, including a comprehensive examination of the cost-benefit ratio, peer-to-peer interactions, and a broader inclusion of diagnostic technologies. (III) Greater emphasis on the involved stakeholders, ranging from patients to stakeholders. In conclusion, this study contributes to a comprehensive and nuanced understanding of the continually evolving landscape in telemedicine technology assessment, offering valuable insights for practitioners, researchers, and policymakers alike. Researchers are encouraged to further explore both the established and emerging themes identified in this study.

Enhancing spatial navigation skills in mild cognitive impairment patients: a usability study of a new version of ANTaging software.

Introduction: Mild Cognitive Impairment (MCI) often presents challenges related to spatial navigation and retention of spatial information. Navigating space involves intricate integration of bodily and environmental cues. Spatial memory is dependent on two distinct frame of reference systems for organizing this information: egocentric and allocentric frames of reference. Virtual Reality (VR) has emerged as a promising technology for enhancing spatial navigation skills and spatial memory by facilitating the manipulation of bodily, environmental, and cognitive cues. Methods: This usability study was based on a fully within-subjects design in which seven MCI patients underwent two kinds of VR conditions: participants were required to complete the ANTaging demo both in Oculus Rift S (immersive condition) and in Samsung UHD 4K monitor (semi-immersive condition). Participants were seated and they had to use a foot-motion pad to navigate and explore the environment to collect and relocate some objects in the virtual environment. Post-interaction, users provided feedback on their experiences. Additionally, usability, potential side effects, data analysis feasibility, and user preferences with immersive and semi-immersive technologies were assessed through questionnaires. Results: Results indicated higher usability ratings for the semi-immersive setup, with fewer negative effects reported compared to the immersive counterpart. According to qualitative analyses of the interviews, patients do seem to like both VR apparatuses even though the semi-immersive condition was perceived as the most suitable choice because of the size of the screen. Patients generally found it difficult to remember object locations. Participants expressed the need for more practice with the foot-motion pad, despite an overall positive experience. They generally would like to use this system to improve their memory. Discussion: Identifying these key aspects was crucial for refining the system before the upcoming clinical trial. This study sheds light on the potential of semi-immersive VR in aiding individuals with MCI, paving the way for enhanced spatial navigation interventions.

Adapting the World Health Organization rapid Assistive Technology Assessment (rATA) to the Italian context: implementation of a TRAPD-based approach.

BACKGROUND: Measuring access to assistive technology (AT) has become a global priority. Recently, the World Health Organization (WHO) has developed the rapid assistive technology assessment (rATA), a population-based household survey that measures the use, need, unmet need, and barriers to accessing AT. OBJECTIVE: The aim of this paper is to report on the translation and adaptation process undertaken to implement the rATA survey in the Italian context. METHOD: The Translate, Review, Adjudicate, Pretest, and Document (TRAPD) approach was used to translate and adapt the rATA from English to Italian. Eleven independent reviewers and 23 AT users were involved to validate the Italian translation of the rATA and pilot the survey, respectively. RESULTS: The feedback provided by the first users of the rATA indicate that the data collected are reliable and well reflect the state of AT provision in Italy. CONCLUSION: This study confirmed the applicability of the rATA survey to the Italian context. The Italian version of the rATA can be used to support the government, the health system as well as the civil society to monitor the current state of AT access (and abandonment) in the country.

Reference theories and future perspectives on robot-assisted rehabilitation in people with neurological conditions: A scoping review and recommendations from the Italian Consensus Conference on Robotics in Neurorehabilitation (CICERONE).

BACKGROUND: Robot-based treatments are developing in neurorehabilitation settings. Recently, the Italian National Health Systems recognized robot-based rehabilitation as a refundable service. Thus, the Italian neurorehabilitation community promoted a national consensus on this topic. OBJECTIVE: To conceptualize undisclosed perspectives for research and applications of robotics for neurorehabilitation, based on a qualitative synthesis of reference theoretical models. METHODS: A scoping review was carried out based on a specific question from the consensus Jury. A foreground search strategy was developed on theoretical models (context) of robot-based rehabilitation (exposure), in neurological patients (population). PubMed and EMBASE® databases were searched and studies on theoretical models of motor control, neurobiology of recovery, human-robot interaction and economic sustainability were included, while experimental studies not aimed to investigate theoretical frameworks, or considering prosthetics, were excluded. RESULTS: Overall, 3699 records were screened and finally 9 papers included according to inclusion and exclusion criteria. According to the population investigated, structured information on theoretical models and indications for future research was summarized in a synoptic table. CONCLUSION: The main indication from the Italian consensus on robotics in neurorehabilitation is the priority to design research studies aimed to investigate the role of robotic and electromechanical devices in promoting neuroplasticity.

Controlled Release of 18-ß-Glycyrrhetinic Acid from Core-Shell Nanoparticles: Effects on Cytotoxicity and Intracellular Concentration in HepG2 Cell Line.

18ß-glycyrrhetinic acid (GA) is a pentacyclic triterpene with promising hepatoprotective and anti-Hepatocellular carcinoma effects. GA low water solubility however reduces its biodistribution and bioavailability, limiting its applications in biomedicine. In this work we used core-shell NPs made of PolyD-L-lactide-co-glycolide (PLGA) coated with chitosan (CS), prepared through an osmosis-based methodology, to efficiently entrap GA. NPs morphology was investigated with SEM and TEM and their GA payload was evaluated with a spectrophotometric method. GA-loaded NPs were administered to HepG2 cells and their efficiency in reducing cell viability was compared with that induced by the free drug in in vitro tests. Cell viability was evaluated by the MTT assay, as well as with Electric Cells-Substrate Impedance Sensing (ECIS), that provided a real-time continuous monitoring. It was possible to correlate the toxic effect of the different forms of GA with the bioavailability of the drug, evidencing the importance of real-time tests for studying the effects of bioactive substances on cell cultures.

Patient-specific three-dimensional aortic arch modeling for automatic measurements: clinical validation in aortic coarctation.

AIM: A validated algorithm for automatic aortic arch measurements in aortic coarctation (CoA) patients could standardize procedures for clinical planning. METHODS: The model-based assessment of the aortic arch anatomy consisted of three steps: first, machine-learning-based algorithms were trained on 212 three-dimensional magnetic resonance (MR) data to automatically allocate the aortic arch position in patients and segment the aortic arch; second, for each CoA patient (N = 33), the min/max aortic arch diameters were measured using the proposed software, manually and automatically, from noncontrast-enhanced three-dimensional steady-state free precession MRI sequence at five selected sites and compared ('internal comparison' referring to the same environment); third, moreover, the same min/max aortic arch diameters were compared, obtaining them independently, manually from common MR management software (MR Viewforum) and automatically from the model (external comparison). The measured sites were: aortic sinus, sino-tubular junction, mid-ascending aorta, transverse arch and thoracoabdominal aorta at the level of the diaphragm. RESULTS: Manual and software-assisted measurements showed a good agreement: the difference between diameter measurements was not statistically significant (at α = 0.05), with only one exception, for both internal and external comparison. A high coefficient of correlation was attained for both maximum and minimum diameters in each site (for internal comparison, R > 0.73 for every site, with P < 2 × 10). Notably, in tricuspid aortic valve patients external comparison showed no statistically significant difference at any measurement sites. CONCLUSION: The automatically derived aortic arch model, starting from three-dimensional MR images, could be a support to take the measurements in CoA patients and to quickly provide a patient-specific model of aortic arch anomalies.

Systems Biology-Driven Hypotheses Tested In Vivo: The Need to Advancing Molecular Imaging Tools.

Processing and interpretation of biological images may provide invaluable insights on complex, living systems because images capture the overall dynamics as a "whole." Therefore, "extraction" of key, quantitative morphological parameters could be, at least in principle, helpful in building a reliable systems biology approach in understanding living objects. Molecular imaging tools for system biology models have attained widespread usage in modern experimental laboratories. Here, we provide an overview on advances in the computational technology and different instrumentations focused on molecular image processing and analysis. Quantitative data analysis through various open source software and algorithmic protocols will provide a novel approach for modeling the experimental research program. Besides this, we also highlight the predictable future trends regarding methods for automatically analyzing biological data. Such tools will be very useful to understand the detailed biological and mathematical expressions under in-silico system biology processes with modeling properties.

Power dissipation associated with surgical operations' hemodynamics: critical issues and application to the total cavopulmonary connection.

The issue of the correct determination of the mechanical power dissipated by the blood flow in the circulatory system is very important. This parameter is particularly critical when the patient's circulation has to overcome structural impairments, such as, e.g., in the case of only one functional ventricle. The surgical palliation of such a condition, which is a relatively common form of congenital heart disease, calls for an optimization of the new connection's hydrodynamics. Starting from the general formulation of the energy dissipation rate in a given control volume, this paper discusses the critical assumptions of the formula usually employed to assess the power dissipation in complex connections, such as the total cavopulmonary connection (TCPC). A new formula is derived, in which the mean elevation of the outlet and inlet sections is shown to be relevant, through the use of the piezometric pressure. Moreover, the flow profile at the boundary of the control volume is also important, since the usual approach implicitly assumes that the flow is perfectly flat: this assumption is doubtful, especially in the venous return (as in the TCPC). In the experimental part of the study, the power dissipation was measured in a physical model of the TCPC, and a large difference was found between the usual method and the proposed one, especially at low regime (85% relative difference, at 1.5 l/min total cardiac output). The proposed approach should be adopted in order to improve the accuracy of the hydrodynamical performance's assessment of surgical connections (e.g., TCPC) or implantable devices (e.g., valved conduit).

A new genotyping scheme based on MLVA for inter-laboratory surveillance of Streptococcus pyogenes.

A newly developed MLVA seven-loci scheme for Streptococcus pyogenes is described. The method can be successfully applied by using both agarose gel with visual inspections of bands and Lab on Chip technology. The potential of the present MLVA has been tested on a collection of 100 clinical GAS strains representing the most common emm types found in high-income countries plus 18 published gap-free genomes, in comparison to PFGE and MLST. The MLVA analysis defined 30 MLVA types with ten out of the considered 15 emm types exhibiting multiple and specific MLVA types. In only one occasion the same MLVA profile was shared between isolates belonging to two different emm types. A robust congruency between the methods was observed, with MLVA discriminating within clonal complexes as defined by PFGE or MLST. This new MLVA scheme can be adopted as a quick, low-cost and reliable typing method to track the short-term diffusion of GAS clones in inter-laboratory-based surveillance.

Prosthetic heart valves' mechanical loading of red blood cells in patients with hereditary membrane defects.

Implantable cardiovascular devices such as prosthetic heart valves (PHVs) are widely applied clinical tools. Upon implantation, the patient can suffer from anemia as a result of red cell destruction and hemolysis can be more relevant whenever the patient is also affected by red cell disorders in which erythrocytes are more susceptible to mechanical stress such as hereditary spherocytosis (HS) and hereditary elliptocytosis (HE). Considering the typical morphological alterations observed in HS and HE, a study of the influence of cell geometry on the distribution of the shear stress on red cells in biological fluids was carried out. A numerical simulation of the loading caused by Reynolds shear stresses on a prolate spheroid was performed, with the ellipticity of the particle as the independent parameter. The average shear stress on a particle in the blood stream was found to depend on the particle's geometry, besides the stress field produced by the prosthetic device. The relevance of an increasing particle ellipticity on the global load is discussed. The model was applied to erythrocytes from implanted patients with HE or HS, enabling to explain the occurrence of moderate or severe anemia, respectively. The clinical data support the relevance of the proposed global parameter as erythrocyte trauma predictor with regard to the fluid dynamics of artificial organs.

A mathematical description of blood spiral flow in vessels: application to a numerical study of flow in arterial bending.

Local arterial haemodynamics has been associated with the pathophysiology of several cardiovascular diseases. The stable spiral blood-flows that were observed in vivo in several vessels, may play a dual role in vascular haemodynamics, beneficial since it induces stability, reducing turbulence in the arterial tree, and accounts for normal organ perfusion, but detrimental in view of the imparted tangential velocities that are involved in plaque formation and development. Being a spiral flow considered representative of the local blood dynamics in certain vessels, a method is proposed to quantify the spiral structure of blood flow. The proposed function, computed along a cluster of particle trajectories, has been tested for the quantitative determination of the spiral blood flow in a three-dimensional, s-shaped femoral artery numerical model in which three degrees of stenosis were simulated in a site prone to atherosclerotic development. Our results confirm the efficacy of the Lagrangian analysis as a tool for vascular blood dynamics investigation. The proposed method quantified spiral motion, and revealed the progression in the degree of stenosis, in the presented case study. In the future, it could be used as a synthetic tool to approach specific clinical complications.

A novel formulation for blood trauma prediction by a modified power-law mathematical model.

With the increasing use of artificial organs, blood damage has been raising ever more clinical concern. Blood trauma is in fact a major complication resulting from the implantation of medical devices and the use of life support apparatuses. Red blood cells damage predictive models furnish critical information on both the design and the evaluation of artificial organs, because their correct usage and implementation are thought to provide clear and rational guidance for the improvement of safety and efficacy. The currently adopted power-law shear-induced haemolysis prediction model lacks sensitivity with respect to the cumulative effect of previously applied stress magnitudes. An alternative model is proposed where a mechanical quantity was defined, able to describe the blood damage sustained by red cells under unsteady stress conditions, taking into account the load history. The proposed formulation predicted the same trend as the available experimental data. The obtained results have to be considered a preliminary validation of the basic hypothesis of this modified red blood cell damage prediction model. To date, the necessity to design further experiments to validate the proposed damage function clashes with the limitations inherent to current systems to get the time-varying shear stress completely under control.

Three-dimensional numeric simulation of flow through an aortic bileaflet valve in a realistic model of aortic root.

A three-dimensional, realistic model of an aortic mechanical heart valve and Valsalva sinuses was developed to predict, by means of a numerical time dependent simulation, the flow field during a fraction of the systolic period. The numeric simulation was performed upon a model of valve similar to a Carbomedics 27 mm placed in a physiologic aortic root shaped model, in which no symmetry planes were exploited to reach a more realistic level. Input data for the simulation have been acquired during an experimental session on the same valve, according to the guidelines of testing protocol for prosthetic heart valves. Flow was assumed to be Newtonian and laminar at low regime and the leaflets fixed in the fully open position. The forward flow of the systolic phase was investigated, and a comparison with experimental results was performed at peak systole, the most representative point of the cardiac cycle. The results of this simulation furnished a reasonable indication (in terms of fluid dynamics) parameters downstream of the prosthetic device, especially in Valsalva sinuses, the role of which is proven to affect the valve's performance.

3D velocity field characterization of prosthetic heart valve with two different valve testers by means of stereo-PIV.

BACKGROUND: Prosthetic heart valves can be associated to mechanical loading of blood, potentially linked to complications (hemolysis and thrombogenicity) which can be clinically relevant. In order to test such devices in pulsatile mode, pulse duplicators (PDs) have been designed and built according to different concepts. This study was carried out to compare anemometric measurements made on the same prosthetic device, with two widely used PDs. METHODS: The valve (a 27-mm bileaflet valve) was mounted in the aortic section of the PD. The Sheffield University PD and the RWTH Aachen PD were selected as physical models of the circulation. These two PDs differ mainly in the vertical vs horizontal realization, and in the ventricular section, which in the RWTH PD allows for storage of potential energy in the elastic walls of the ventricle. A glassblown aorta, realized according to the geometric data of the same anatomical district in healthy individuals, was positioned downstream of the valve, obtaining 1:1 geometric similarity conditions. A NaI-glycerol-water solution of suitable kinematic viscosity and, at the same time, the proper refractive index, was selected. The flow field downstream of the valve was measured by means of the stereo-PIV (Particle Image Velocimetry) technique, capable of providing the complete 3D velocity field as well as the entire Reynolds stress tensor. The measurements were carried out at the plane intersecting the valve axis. RESULTS: A three-jet profile was clearly found in the plane crossing the leaflets, with both PDs. The extent of the typical recirculation zone in the Valsalva sinus was much larger in the RWTH PD, on account of the different duration of the swirling motion in the ventricular chamber, caused by the elasticity of the ventricle and its geometry. CONCLUSION: The comparison of the hemodynamical behaviour of the same bileaflet valve tested in two PDs demonstrated the role of the mock loop in affecting the valve performance.

The beneficial vortex and best spatial arrangement in total extracardiac cavopulmonary connection.

OBJECTIVE: Total extracardiac cavopulmonary connection is an established procedure, but the best spatial arrangement remains controversial. On the basis of our clinical experience with total extracardiac cavopulmonary connection, we performed quantitative and qualitative flow analysis on total extracardiac cavopulmonary connection models simulating the two most frequent arrangements applied to our patients to determine the most favorable hydrodynamic pattern. METHODS: We selected two main groups among 110 patients who underwent total extracardiac cavopulmonary connection, those with left-sided inferior vena cava anastomosis (type 1) and those with facing superior and inferior vena cava anastomoses (type 2). Blown-glass total extracardiac cavopulmonary connection phantom models were constructed on the basis of nuclear magnetic resonance and angiographic images. Flow measurements were performed with a Nd:YAG Q-switched laser and a particle imaging velocimetry system. A power dissipation study and a finite-element numeric simulation were also carried out. RESULTS: When applying superior and inferior vena caval flow proportions of total systemic venous return of 40% and 60%, respectively, a vortex was visualized in the type 1 phantom that rotated counterclockwise at the junction of the caval streams. This apparent vortex was not a true vortex; rather, it represented a weakly dissipative recirculating zone modulating the flow distribution into the pulmonary arteries. The power dissipation and finite-element numeric stimulation confirmed the beneficial nature of the apparent vortex and a more energy-saving pattern in the type 1 phantom than in the type 2 phantom. CONCLUSION: Total extracardiac cavopulmonary connection with left-sided diversion of the inferior vena caval conduit anastomosis is characterized by a central vortex that regulates the caval flow partitioning and provides a more favorable energy-saving pattern than is seen with the total extracardiac cavopulmonary connection with directly opposed cavopulmonary anastomoses.

Evaluation of the surface-averaged load exerted on a blood element by the Reynolds shear stress field provided by artificial cardiovascular devices.

Implantable prosthetic devices can often affect the recipient's hemostasis, with possible hemolysis and thrombus formation. Since such devices can produce turbulent flow, it is important to characterize it as accurately as possible, by means of the Reynolds stress tensor. Some parameters related to the latter have been often used to provide a quantity related to the possible damage to blood constituents: the TSS(max), for instance, has been associated with hemolysis. It can be expressed as TSS(max)=(sigma(1)-sigma(3))/2, sigma(1) and sigma(3) being the highest and lowest principal normal stresses (PNSs) in each point of the flow. In the present work, the average value of the shear stress over a spherical surface, representative of a blood component, is derived. All three PNSs (sigma(1), sigma(2) and sigma(3)) are found to have an equal role in the determination of this parameter, since the relative formula shows a marked symmetry with respect to the PNSs. The average shear stress level, for a given (sigma(1), sigma(3)) pair (hence, for a given TSS(max)), has a minimum and maximum value, depending on the particular sigma(2) value yielded by the local structure of the turbulent flow field. A numerical investigation on more complex geometries shows similar results. The role of the intermediate PNS is thus shown for the first time to have a physical relevance. The presented results can be useful whenever a spatial averaging of the shear field is important to be assessed, such as in the case of platelet activation. A new parameter is thus proposed, which can be correlated with prosthetic devices complications.