Sled acceleration control for low speed impact testing and transient response studies

Whiplash Associated Disorder is the most common soft-tissue injury arising from low-speed car crashes (Siskind et al. 2013). To better understand whiplash injury mechanisms in the head-neck system, a sled was acquired. The sled was previously controlled in open loop mode, without any feedback of the resulting motion. The aim of this project is to safely control the motion and acceleration of the sled in order to be able to generate reproducible acceleration profiles.FSR (Fondation Sécurité Routière

Transient Response of the Head Kinematics - Influence of a Disturbed Visual Flow

Vision influences the controlled kinematics of human body. Previous studies have shown the influence of vision on head stabilization or whole posture. However, latencies between the stimuli and the head motion have never been quantified. The aim of this study is to quantify the influence of a perturbed vision on the head kinematics. Seven healthy volunteers without uncorrected vision (26.7±6.9 years old, 1 female, 2 right-handed/right-dominant eye, 5 right-handed/left-dominant eye) were studied. Visual stimuli were performed through an immersive personal 3D viewer (HMZ-T1, Sony), securely tied on the head. Motion analysis of the head and the torso were performed using the optoelectronic Vicon system (100Hz). Three markers were glued on the personal viewer, close to the nasion, left and right tragus, in order to create the head frame. Three markers were glued to create the torso frame (both acromia and C7). Two different 3D animated scenes were created on Blender and displayed at 24Hz. The first animation was a landscape with a ball rolling on the ground, and then the ball stopped before being virtually launched via a catapult toward the screen. Two velocities were programmed: 4.67 and 10.58 m.s-1. The second animation was a beach with sea and sky, where horizon tilted anticlockwise at 2 different constant rates: 0.24 deg.s-1 and 0.48 deg.s-1 with maximal amplitude of 8° and 16° respectively. The motion of the head relative to the torso was calculated for both scenes on seated and upright position, at the 2 different velocities, 2 times each, for a total of 16 random tests on each volunteer. For the launched ball animated scene, the reaction time seated was, as expected, shorter for the fast launches. For the beach animated scene, the head profiles followed most of the time the kinematic profile of the tilted animation, linearly or by steps, and not necessary until the end. Volunteers who were right-handed and right dominant eye tilted their head clockwise, at the inverse of the stimuli. Both experiments confirmed that visual stimulus could influence the kinematics of the head-neck system. In the ball animation, velocity of the stimulus does not seem to affect the amplitude of movement. In the beach animation, the head motions were variable, but performed at the same mean speed than the stimuli. Furthermore, the limited number of volunteer cannot conclude on the direction of rotation of the head, depending of the dominant hand and eye

Contribution à la modélisation géométrique et mécanique du tronc de l'enfant

Despite of the use of homologated Child Restraint Systems, 2,321 children were killed on European roads in 2007. This social and economical major issue is explained by the lack of biomechanical knowledge on injury mechanisms and associated physical parameters, specifically for children. The present project was supported by the GDR “Biomécanique des chocs“ (CNRS/INRETS/GIE PSA Renault) and funded by the French National Research Agency. The aim of this study is to improve the biomechanical knowledge of the children trunk. The dynamic response of the trunk is essential because it is the main segment used for the whole body restraint when a car crash occurs. In order to improve the reliability of children's models, subject-specific inertial parameters of the body segments were calculated using 3D reconstructions from low dose biplanar X-rays. The fine description of the ribs, costal cartilage and sternum was performed on 3D models from CT-scan. The 3D geometry of the intra-abdominal child organs (kidney, spleen and liver) was defined by measurements based upon 3D modeling using abdominal CT-scan. The quantification of the thoracic and abdominal behaviors was obtained in observing in vivo trunk manipulations carried out within the framework of usual physiotherapist treatments. This research will be used to improve or develop the trunk bio-fidelity of child models and constitute a first step toward an enhanced knowledge of the child biomechanics based directly on in vivo experimentation.Malgré l'obligation d'utiliser des Dispositifs de Retenue Enfant homologués, 2 321 enfants ont été tués en 2007 sur les routes européennes. Ce problème socio-économique majeur est expliqué par le manque de connaissance biomécanique de l'enfant. Le développement de modèles d'enfant nécessite la compréhension de ses paramètres biomécaniques et critères lésionnels. Ce projet, supporté par le GDR « Biomécanique des chocs » (CNRS/INRETS/GIE PSA Renault) et financé par l'Agence Nationale de la Recherche (ANR-06-BLAN-0385 SECUR_ENFANT), a pour objectif de contribuer à l'amélioration de ces connaissances, en s'intéressant particulièrement au tronc de l'enfant. La réponse mécanique de ce segment corporel est essentielle car c'est le principal composant utilisé lors de la retenue en choc automobile. Les paramètres inertiels des segments corporels ont été calculés à partir de reconstructions personnalisées 3D issues de radiographies biplanaires basse dose. La description précise des côtes, du cartilage costal et du sternum a été évaluée à partir de modélisations 3D issues de données d'imagerie scanner. Des reconstructions de reins, rates et foies à partir de scanners abdominaux ont permis de définir la géométrie et le positionnement de ces organes dans le système ostéoarticulaire. Enfin, le comportement mécanique du thorax et de l'abdomen d'enfants a été quantifié à partir de manipulations in vivo faites en routine clinique de kinésithérapie respiratoire. Les résultats de ce travail, basés sur des examens in vivo, sont utiles à l'amélioration de la biofidélité du tronc des modèles d'enfants et contribuent à l'approfondissement des connaissances biomécaniques de l'enfant

Variability of Child Rib Bone Hounsfield Units using in vivo Computed Tomography

The variability assessment of the rib bone mechanical properties during the growth process is still missing. These properties could not be obtained in vivo on children. Relationships have been obtained between Hounsfield Units from computed tomography (CT) and mechanical properties (e.g. for the cortical bone on adults). As a first step for investigation of the mechanical properties of child ribs, the aim of this study was to determine the Hounsfield Units variation of child ribs from CT‐scan data, by rib level, along the rib and within the rib sections. Twenty‐seven right ribs of levels 4, 6 and 9 were processed from 11 thoracic CT scans of children without bone lesions aged between 1 and 10 years. A first set of 10 equidistributed cross‐sections normal to the rib midline were extracted. Sixteen equally distributed elements defined 4 areas into the cortical band: internal, external, caudal and cranial. Within the rib sections, Hounsfield Units were found significantly higher in internal and external areas than in caudal and cranial. In a further step using calibrated CT scans, it would be possible to derive the mechanical properties of in vivo child ribs using bone density correlation with Hounsfield Units

Quantitative geometric analysis of rib, costal cartilage and sternum from childhood to teenagehood

Better understanding of the effects of growth on children’s bones and cartilage is necessary for clinical and biomechanical purposes. The aim of this study is to define the 3D geometry of children’s rib cages: including sternum, ribs and costal cartilage. Three-dimensional reconstructions of 960 ribs, 518 costal cartilages and 113 sternebrae were performed on thoracic CT-scans of 48 children, aged four months to 15 years. The geometry of the sternum was detailed and nine parameters were used to describe the ribs and rib cages. A "costal index" was defined as the ratio between cartilage length and whole rib length to evaluate the cartilage ratio for each rib level. For all children, the costal index decreased from rib level one to three and increased from level three to seven. For all levels, the cartilage accounted for 45 to 60% of the rib length, and was longer for the first years of life. The mean costal index decreased by 21% for subjects over three years old compared to those under three (p<10-4). The volume of the sternebrae was found to be highly age dependent. Such data could be useful to define the standard geometry of the paediatric thorax and help to detect clinical abnormalities.Grant from the ANR (SECUR_ENFANT 06_0385) and supported by the GDR 2610 “Biomécanique des chocs” (CNRS/INRETS/GIE PSA Renault

Evaluation of a Passive Model to Mimic Dynamic Head/Neck Movements

The aim of the present study is to model the dynamic of the head/neck complex to understand muscle stabilization strategies. The boundary conditions of the model are based on previous in vivo experiments on 20 volunteers seated on an accelerated sled in frontal direction (Sandoz et al. 2016). Some of these volunteers performed EOS Xray images in order to personnalize geometrical parameters. EOS imaging system is a low dose X-rays acquisition system allowing to perform bi-planar acquisition of the subject’s cervical spine. From these X-rays, the 3D personalized geometry of each volunteer’s head neck complex can be built

In vivo assessment of the mechanical properties of the child cortical bone using quantitative computed tomography

The mechanical properties of the rib cortical bone are extremely rare on children due to difficulties to obtain specimens to perform conventional tests. Some recent studies used cadaveric bones or bone tissues collected during surgery but are limited by the number of samples that could be collected. A non-invasive technique could be extremely valuable to overcome this limitation. It has been shown that a relationship exists between the mechanical properties (apparent Young’s modulus and ultimate strength) and the bone mineral density (assessed using Quantitative Computed Tomography, QCT), for the femur and recently by our group for the adult ribs ex vivo. Thus the aim of this study was to assess the mechanical properties of the child rib cortical bone using both QCT images in vivo and the previous relationship between bone mineral density and mechanical properties of the rib cortical bone. Twenty-eight children were included in this study. Seven age-groups have been considered (1, 1.5, 3, 6, 10, 15, 18 years old). The QCT images were prescribed for various thoracic pathologies at the pediatric hospital in Lyon. A calibration phantom was added to the clinical protocol without any modifications for the patient. The protocol was approved by the ethical committee. A 3D reconstruction of each thorax was performed using the QCT images. A custom software was then used to obtain cross-sections to the rib midline. The mean bone mineral density was then computed by averaging the Hounsfield Units in a specific cross-section and by converting the mean value (Hounsfield Units) in bone mineral density using the calibration phantom. This bone mineral density was assessed for the 6th rib of each subject. Our relationship between the bone mineral density and the mechanical properties of the rib cortical bone was used to derive the mechanical properties of the child ribs in vivo. The results give values for the apparent Young’s modulus and the ultimate strength. The mechanical properties increase along growth. As an example the apparent Young’s modulus in the lateral region ranges from 7 GPa +/-3 at 1 year old up to 13 GPa +/- 2 at 18 years old. These data are in agreement with the few previous values obtained from child tissues. This methodology opens the way to in vivo measurement of the mechanical properties of the child cortical bone based on calibrated QCT images

Non-invasive assessment of human multifidus muscle stiffness using ultrasound shear wave elastography: A feasibility study

INTRODUCTION: There is a lack of numeric data for the mechanical characterization of spine muscles, especially in vivo data. The multifidus muscle is a major muscle for the stabilization of the spine and may be involved in the pathogenesis of chronic low back pain (LBP). Supersonic shear wave elastography (SWE) has not yet been used on back muscles. The purpose of this prospective study is to assess the feasibility of ultrasound SWE to measure the elastic modulus of lumbar multifidus muscle in a passive stretching posture and at rest with a repeatable and reproducible method. METHOD: A total of 10 asymptotic subjects (aged 25.5±2.2 years) participated, 4 females and 6 males. Three operators performed 6 measurements for each of the 2 postures on the right multifidus muscle at vertebral levels L2-L3 and L4-L5. Repeatability and reproducibility have been assessed according to ISO 5725 standard. RESULTS: Intra-class correlation coefficients (ICC) for intra- and inter observer reliability were rated as both excellent [ICC=0.99 and ICC=0.95, respectively]. Reproducibility was 11% at L2-L3 level and 19% at L4-L5. In the passive stretching posture, shear modulus was significantly higher than at rest (u<0.05). DISCUSSION: This preliminary work enabled to validate the feasibility of measuring the shear modulus of the multifidus muscle with SWE. This kind of measurement could be easily introduces into clinical routine like for the medical follow-up of chronic LBP or scoliosis treatments.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling for funding (with the support of ParisTech and Yves Cotrel Foundations, Société Générale, Proteor and Covea)

Group Creativity in Biomedical Engineering Education

Aim: The present study focuses on a group creativity approach tested during a 5-day interdisciplinary seminar involving 12 members of the teaching team, a creativity facilitator and 87 students from various nationalities enrolled in 4 specialities of a Biomedical Master. Approach: 15 multidisciplinary teams of 5 to 6 students were formed according to their background and specialities. Questionnaires were used to assess students’ thinking styles and teamwork capability. Students were introduced to the six thinking hats technique and to an adapted version of Human Centred Design. During the creativity sessions, students were encouraged to think about things that have frustrated them lately, to find an idea, define what the problem is and “solve” it. The last day, students voted for each project in terms of originality, impact and feasibility. A jury of experts gave a mark (out of 20) to each project. Results: All the projects involved the development of a smart technical device to diagnose, detect, monitor, cure or prevent a health problem such as diabetes, sleep disorder, sudden death syndrome, snake bite, epilepsy, bed sore, posture or hormonal issues. Jury marks were positively correlated with the peer feasibility and impact votes but not with the originality of the projects. The dominant thinking style of the students was “Pragmatist” (42% of student with score ≥60). The team who received the highest number of votes and the highest jury mark (18 out of 20) included students with different thinking styles (Synthesist, Pragmatist, Realist and Analyst). The 6 teams in which there was at least one member with "Realist" dominant thinking style obtained 63% of peers’ feasibility votes. The lowest jury mark (14 out of 20) was awarded to the team including members with only 2 different thinking styles, "Synthesist" and "Idealist". Students with preference for "Synthesist" thinking style perceived their teamwork as less efficient. Conclusion: The approach used was well received by students and the outcome was very satisfactory. Feasibility and impact are favoured over originality by the students and their mentors. Teamwork seems to be influenced by the diversity of the thinking styles of the teams ‘members. The main guidelines developed to improve the teaching of creativity tools concern a) the composition of innovation teams: in addition to the diversity of backgrounds and specialities a more structured approach to form teams should involves measuring team member’s thinking preferences before forming a team and balancing it accordingly, b) thinking style awareness: it could be interesting that one identifies each strategic thinking to leverage strengths and to reinforce or modify those thinking styles

Intra cranial volume quantification from 3D reconstruction based on CT-scan data

The evolution of some congenital diseases impacting the shape of the skull such as the Chiari malformation or Craniosynostosis condition can be quantify measuring the increasing of the intra cranial volume (ICV) (Gault et al. 1993). This volume could be calculated from ana-tomic measurements (Gordon 1966). Nevertheless, in case of important variations of shape, these techniques were not suitable to accurately assess ICV from measure-ments of global parameters. Some studies, using automatic segmentation combined with manual adjustments from MRI acquisition were used to assess the ICV (Reite et al. 2010). However, 3-4 hours were required for each patient to complete the process. Other studies used total auto-matic segmentation to calculate volume of the brain and the ICV (de Jong et al. 2017). But high quality of MRI was necessary to get accurate results.The purpose of this study was to develop a fast, efficient and reproducible procedure to calculate the ICV, based on 3D skull reconstruction obtained from scanner imaging