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      Experimental and Modeling Analyses of Human Motion Across the Static Magnetic Field of an MRI Scanner

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          Abstract

          It is established that human movements in the vicinity of a permanent static magnetic field, such as those in magnetic resonance imaging (MRI) scanners induce electric fields in the human body; this raises potential severe risks of health to radiographers and cleaners exposed routinely to these fields in MRI rooms. The relevant directives and parameters, however, are based on theoretical models, and accurate studies on the simulation of the effects based on human movement data obtained in real conditions are still lacking. Two radiographers and one cleaner, familiar with MRI room activities and these directives, were gait analyzed during the execution of routine job motor tasks at different velocities. Full body motion was recorded in a gait laboratory arranged to reproduce the workspace of a room with an MRI full-body scanner. Body segments were tracked with clusters of at least three markers, from which position and velocity of the centroids were calculated. These were used as input in an established computer physical model able to map the stray field in an MRI room. The spatial peak values of the calculated electric field induced by motion of the head and of the entire body during these tasks, for both the health and sensory effects, were found smaller than the thresholds recommended by the European directives, for both 1.5 T and 3.0 T MRI. These tasks therefore seem to guarantee the safety of MRI room operators according to current professional good practice for exposure risks. Physical modeling and experimental measures of human motion can also support occupational medicine.

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          Human movement analysis using stereophotogrammetry. Part 3. Soft tissue artifact assessment and compensation.

          When using optoelectronic stereophotogrammetry, skin deformation and displacement causes marker movement with respect to the underlying bone. This movement represents an artifact, which affects the estimation of the skeletal system kinematics, and is regarded as the most critical source of error in human movement analysis. A comprehensive review of the state-of-the-art for assessment, minimization and compensation of the soft tissue artifact (STA) is provided. It has been shown that STA is greater than the instrumental error associated with stereophotogrammetry, has a frequency content similar to the actual bone movement, is task dependent and not reproducible among subjects and, of lower limb segments, is greatest at the thigh. It has been shown that in in vivo experiments only motion about the flexion/extension axis of the hip, knees and ankles can be determined reliably. Motion about other axes at those joints should be regarded with much more caution as this artifact produces spurious effects with magnitudes comparable to the amount of motion actually occurring in those joints. Techniques designed to minimize the contribution of and compensate for the effects of this artifact can be divided up into those which model the skin surface and those which include joint motion constraints. Despite the numerous solutions proposed, the objective of reliable estimation of 3D skeletal system kinematics using skin markers has not yet been satisfactorily achieved and greatly limits the contribution of human movement analysis to clinical practice and biomechanical research. For STA to be compensated for effectively, it is here suggested that either its subject-specific pattern is assessed by ad hoc exercises or it is characterized from a large series of measurements on different subject populations. Alternatively, inclusion of joint constraints into a more general STA minimization approach may provide an acceptable solution.
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            Normal walking speed: a descriptive meta-analysis.

            Walking speed has implications for community functioning and is predictive of important outcomes. Determining whether an individual's walking speed is limited requires normal values for comparison. To use meta-analysis to describe normal gait speed for healthy individuals within age and gender strata. PubMed, the Cumulative Index of Nursing and Allied Health (CINAHL), Scopus, Science Citation Index and articles identified by hand searches. Inclusion required that the gait speed of apparently healthy adults was documented as they walked at a normal pace over a course of 3 to 30 m. Summary data were excluded unless obtained from at least 10 participants within a gender and decade stratum. The two authors independently reviewed articles and extracted data. Accuracy was confirmed by the other author. Data were grouped within gender and decade strata. A meta-analysis macro was used to consolidate data by strata and to determine homogeneity. Forty-one articles contributed data to the analysis. Combined, they provided data from 23111 subjects. The gait speed was homogeneous within strata and ranged from a mean of 143.4 cm/second for men aged 40 to 49 years to a mean of 94.3 cm/second for women aged 80 to 99 years. The data presented herein may not be useful as a standard of normal if gait is measured over short distances from the command 'go' or if a turn is involved. The consolidation of data from multiple studies reported in this meta-analysis provides normative data that can serve as a standard against which individuals can be compared. Doing so will aid the interpretation of their performance. Copyright © 2011 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
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              A new anatomically based protocol for gait analysis in children.

              Human movement analysis still suffers from the weakness of the currently used protocols for data collection and reduction. Reliable data comparisons and precise functional assessment require anatomically based definitions of the reference axes and frames, and therefore careful identification and tracking of the landmarks. When impaired children are analysed, the marker-set and other measurement procedures have to be minimised to reduce the time of the experiment and ensure patient collaboration. A new protocol is proposed for the analysis of pelvis and lower limb motion obtained as a compromise between these two requirements. A marker-set is proposed which involves the attachment of 22 skin markers, the calibration by a pointer of 6 anatomical landmarks, and the identification of the hip joint centre by a prediction approach. Anatomical reference frames and joint rotations are defined according to current recommendations. The protocol was assessed by analysing a single child in several repetitions by different examiners, and a population of 10 healthy children, mean age 9.7-years-old. The entire analysis was repeated after subtraction of the offset by static posture angles. The minimum and maximum means of the standard deviations from five examiners of the same child were respectively 2.1 degrees in pelvic obliquity and 6.8 degrees in knee rotation. The minimum and maximum means of the standard deviations from the 10 healthy children were 2.1 degrees in pelvic obliquity and 9.6 degrees in knee internal-external rotation. The protocol is feasible and allows 3D anatomical-based measurements of segment and joint motion and data sharing according to current standards.
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                Author and article information

                Contributors
                Journal
                Front Bioeng Biotechnol
                Front Bioeng Biotechnol
                Front. Bioeng. Biotechnol.
                Frontiers in Bioengineering and Biotechnology
                Frontiers Media S.A.
                2296-4185
                05 May 2021
                2021
                : 9
                : 613616
                Affiliations
                [1] 1Advanced Radiation Oncology Department, Cancer Care Center, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Sacro Cuore Don Calabria Hospital , Negrar di Valpolicella, Italy
                [2] 2Dipartimento di Fisica e Chimica, Università degli Studi di Palermo , Palermo, Italy
                [3] 3Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Ortopedico Rizzoli, Movement Analysis Laboratory , Bologna, Italy
                [4] 4Azienda Ospedaliera di Rilievo Nazionale e di Alta Specializzazione (A.R.N.A.S.) Civico–Di Cristina–Benfratelli, Unità Operativa Complessa (U.O.C.) Fisica Sanitaria , Palermo, Italy
                [5] 5Villa Santa Teresa, Unità Operativa (U.O.) Fisica Sanitaria , Bagheria, Italy
                [6] 6Dipartimento di Scienze Biomediche, Odontoiatriche e delle Immagini Morfologiche e Funzionali (BIOMORF), Università degli Studi di Messina , Messina, Italy
                [7] 7Scuola di Specializzazione in Fisica Medica, Università degli Studi di Messina , Messina, Italy
                Author notes

                Edited by: Simone Tassani, Pompeu Fabra University, Spain

                Reviewed by: Xiaojun Chen, Shanghai Jiao Tong University, China; Michele Raggi, Turingsense EU Lab s.r.l, Italy

                *Correspondence: Davide Gurrera davide.gurrera@ 123456sacrocuore.it

                This article was submitted to Biomechanics, a section of the journal Frontiers in Bioengineering and Biotechnology

                Article
                10.3389/fbioe.2021.613616
                8131562
                2287d70d-9b3f-417e-a032-bf7645fa3578
                Copyright © 2021 Gurrera, Leardini, Ortolani, Durante, Caputo, Gallias, Abbate, Rinaldi, Iacoviello, Acri, Vermiglio and Marrale.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 02 October 2020
                : 10 March 2021
                Page count
                Figures: 12, Tables: 3, Equations: 4, References: 25, Pages: 10, Words: 5755
                Categories
                Bioengineering and Biotechnology
                Original Research

                human movement analysis,static magnetic fields,exposure limit values,mri personnel safety,directive 2013/35/eu

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