Shell finite element model for interactive fetal head deformation during childbirth

International audienceIn this paper, we design a flat shell finite element model in order to simulate the fetal head deformation during childbirth. This new method also guarantees the incompressibility of the fetal head enclosed volume

Personalized modeling for real-time pressure ulcer prevention in sitting posture

, Ischial pressure ulcer is an important risk for every paraplegic person and a major public health issue. Pressure ulcers appear following excessive compression of buttock's soft tissues by bony structures, and particularly in ischial and sacral bones. Current prevention techniques are mainly based on daily skin inspection to spot red patches or injuries. Nevertheless, most pressure ulcers occur internally and are difficult to detect early. Estimating internal strains within soft tissues could help to evaluate the risk of pressure ulcer. A subject-specific biomechanical model could be used to assess internal strains from measured skin surface pressures. However, a realistic 3D non-linear Finite Element buttock model, with different layers of tissue materials for skin, fat and muscles, requires somewhere between minutes and hours to compute, therefore forbidding its use in a real-time daily prevention context. In this article, we propose to optimize these computations by using a reduced order modeling technique (ROM) based on proper orthogonal decompositions of the pressure and strain fields coupled with a machine learning method. ROM allows strains to be evaluated inside the model interactively (i.e. in less than a second) for any pressure field measured below the buttocks. In our case, with only 19 modes of variation of pressure patterns, an error divergence of one percent is observed compared to the full scale simulation for evaluating the strain field. This reduced model could therefore be the first step towards interactive pressure ulcer prevention in a daily setup. Highlights-Buttocks biomechanical modelling,-Reduced order model,-Daily pressure ulcer prevention

Biomechanical Lower Limb Model to Predict Patellar Position Alteration after Medial Open Wedge High Tibial Osteotomy

Medial open-wedge high tibial osteotomy is a surgical treatment for patients with a varus deformity and early-stage medial knee osteoarthritis. Observations suggest that this surgery can negatively affect the patellofemoral joint and change the patellofemoral kinematics. However, what causes these effects and how the correction angle can change the surgery's impact on the patellofemoral joint has not been investigated before. The objective of this study was to develop a biomechanical model that can predict the surgery's impact on the patellar position and find the correlation between the opening angles and the patellar position after the surgery. A combined finite element and multibody model of the lower limb was developed. The model's capabilities for predicting the patellofemoral kinematics were evaluated by performing a passive deep flexion simulation of the native knee and comparing the outcomes with magnetic resonance images of the study subject at various flexion angles. The model at a fixed knee flexion angle was then used to simulate the high tibial osteotomy surgery virtually. The results showed a correlation between the wedge opening angles and the patellar position in various degrees of freedom. These results indicate that larger wedge openings result in increased values of patellar distalization, lateral patellar shift, patellar rotation, and patellar internal tilt. The developed model in this study can be used in future studies to monitor the stress distribution on the patellar cartilage and connecting tissues to investigate their relationship with observations of pain and cartilage injury due to post-operative altered patellar kinematics

Using CamiTK for rapid prototyping of interactive Computer Assisted Medical Intervention applications

Computer Assisted Medical Intervention (CAMI hereafter) is a complex multi-disciplinary field. CAMI research requires the collaboration of experts in several fields as diverse as medicine, computer science, mathematics, instrumentation, signal processing, mechanics, modeling, automatics, optics, etc

Diatom DNA metabarcoding for ecological assessment: Comparison among bioinformatics pipelines used in six European countries reveals the need for standardization

Ecological assessment of lakes and rivers using benthic diatom assemblages currently requires considerable taxonomic expertise to identify species using light microscopy. This traditional approach is also time-consuming. Diatom metabarcoding is a promising alternative and there is increasing interest in using this approach for routine assessment. However, until now, analysis protocols for diatom metabarcoding have been developed and optimised by research groups working in isolation. The diversity of existing bioinformatics methods highlights the need for an assessment of the performance and comparability of results of different methods. The aim of this study was to test the correspondence of outputs from six bioinformatics pipelines currently in use for diatom metabarcoding in different European countries. Raw sequence data from 29 biofilm samples were treated by each of the bioinformatics pipelines, five of them using the same curated reference database. The outputs of the pipelines were compared in terms of sequence unit assemblages, taxonomic assignment, biotic index score and ecological assessment outcomes. The three last components were also compared to outputs from traditional light microscopy, which is currently accepted for ecological assessment of phytobenthos, as required by the Water Framework Directive. We also tested the performance of the pipelines on the two DNA markers (rbcL and 185-V4) that are currently used by the working groups participating in this study. The sequence unit assemblages produced by different pipelines showed significant differences in terms of assigned and unassigned read numbers and sequence unit numbers. When comparing the taxonomic assignments at genus and species level, correspondence of the taxonomic assemblages between pipelines was weak. Most discrepancies were linked to differential detection or quantification of taxa, despite the use of the same reference database. Subsequent calculation of biotic index scores also showed significant differences between approaches, which were reflected in the final ecological assessment. Use of the rbcL marker always resulted in better correlation among molecular datasets and also in results closer to these generated using traditional microscopy. This study shows that decisions made in pipeline design have implications for the dataset's structure and the taxonomic assemblage, which in turn may affect biotic index calculation and ecological assessment. There is a need to define best-practice bioinformatics parameters in order to ensure the best representation of diatom assemblages. Only the use of similar parameters will ensure the compatibility of data from different working groups. The future of diatom metabarcoding for ecological assessment may also lie in the development of new metrics using, for example, presence/absence instead of relative abundance data. (C) 2020 The Authors. Published by Elsevier B.V

Modèles biomécaniques pour la simulation interactive de l'accouchement

The training to obstetrical gestures performed directly on the patient raise ethical and medico-legal problems. That is why most of the formation is based on in-situ observations. This approach can not handle all the necessary dimensions to the formation such as instrumental extraction, a good level of dexterity or the capacity to take decision in high risk situations.Simulation based training systems can address this formation problems. Neverteless, today's haptic simulators don't provide quantitative informations about the efforts undergone by pelvic organs. This informations are available only through biomechanical simulations of the foetal descent. To be used in conjunction with an haptic simulator, such simulations must be interactive.In this manuscript, first we propose a state of the art of the existing biomechanical models allowing to model the pelvic organs. After having identified the foetal head as the structure that can potentially undergo important damages during childbirth, we present a model of the foetal head based on shell finite elements CST-DKT that we extend to a co-rotationnal formulation and a volume constraint allowing to take in count the intra-cranial matter. A GPU implementation of this model is also porposed to allow interactive simulations. This model is validated on a simulation of intra-uterine pressure undergone by the foetal head during the second phase of childbirth. Finally, we propose a draft of a complete model intended to simulate interactively the feotal descent.La formation aux gestes en obstétrique réalisée directement auprès du patient pose des problèmes éthiques et médico-légaux. C'est pourquoi une grande partie de cette formation repose sur l'observation in-situ. Cette approche ne permet pas de prendre en charge l'ensemble des dimensions nécessaires à la formation telles que l'extraction instrumentale, l'acquisition d'un niveau de dextérité suffisant ou encore la capacité de prise de décision face à une situation à risque.Les systèmes d'entrainement par simulation consituent une réponse à ce problème de formation. Toutefois, les simulateurs haptiques actuels ne permettent qu'une évaluation qualitative du geste obstétrique et ne fournissent pas d'informations quantitatives sur les efforts subis par les différents organes pelviens. Ces informations quantitatives ne sont accessibles que par des simulation biomécaniques de la descente fœtale. Par contre, pour pouvoir être utilisées conjointement avec un simulateur haptique dans un but d'apprentissage, ces simulations doivent être interactives.Dans ce manuscrit, nous proposons tout d'abord un état de l'art des différents modèles biomécaniques existants permettant de modéliser les organes pelviens et la descente fœtale. Après avoir identifié la tête foetale comme la structure la plus susceptible de subir des dommages importants lors de l'accouchement, nous présentons un modèle de la tête foetale basé sur des éléments finis de coque CST-DKT que nous étendons avec un formulation co-rotationelle et une contrainte de volume permettant de prendre en compte la matière intra-crânienne. Une implémentation GPU de ce modèle est proposée pour permettre des simulations interactives. Ce modèle est validé sur une simulation de la pression intra-utérine subie par la tête fœtale lors de la deuxième phase de l'accouchement. Enfin, nous proposons une ébauche de modèle complet pour la simulation interactive de la descente fœtale

Biomechanical models for interactive simulation of childbirth

La formation aux gestes en obstétrique réalisée directement auprès du patient pose des problèmes éthiques et médico-légaux. C'est pourquoi une grande partie de cette formation repose sur l'observation in-situ. Cette approche ne permet pas de prendre en charge l'ensemble des dimensions nécessaires à la formation telles que l'extraction instrumentale, l'acquisition d'un niveau de dextérité suffisant ou encore la capacité de prise de décision face à une situation à risque.Les systèmes d'entrainement par simulation consituent une réponse à ce problème de formation. Toutefois, les simulateurs haptiques actuels ne permettent qu'une évaluation qualitative du geste obstétrique et ne fournissent pas d'informations quantitatives sur les efforts subis par les différents organes pelviens. Ces informations quantitatives ne sont accessibles que par des simulation biomécaniques de la descente fœtale. Par contre, pour pouvoir être utilisées conjointement avec un simulateur haptique dans un but d'apprentissage, ces simulations doivent être interactives.Dans ce manuscrit, nous proposons tout d'abord un état de l'art des différents modèles biomécaniques existants permettant de modéliser les organes pelviens et la descente fœtale. Après avoir identifié la tête foetale comme la structure la plus susceptible de subir des dommages importants lors de l'accouchement, nous présentons un modèle de la tête foetale basé sur des éléments finis de coque CST-DKT que nous étendons avec un formulation co-rotationelle et une contrainte de volume permettant de prendre en compte la matière intra-crânienne. Une implémentation GPU de ce modèle est proposée pour permettre des simulations interactives. Ce modèle est validé sur une simulation de la pression intra-utérine subie par la tête fœtale lors de la deuxième phase de l'accouchement. Enfin, nous proposons une ébauche de modèle complet pour la simulation interactive de la descente fœtale.The training to obstetrical gestures performed directly on the patient raise ethical and medico-legal problems. That is why most of the formation is based on in-situ observations. This approach can not handle all the necessary dimensions to the formation such as instrumental extraction, a good level of dexterity or the capacity to take decision in high risk situations.Simulation based training systems can address this formation problems. Neverteless, today's haptic simulators don't provide quantitative informations about the efforts undergone by pelvic organs. This informations are available only through biomechanical simulations of the foetal descent. To be used in conjunction with an haptic simulator, such simulations must be interactive.In this manuscript, first we propose a state of the art of the existing biomechanical models allowing to model the pelvic organs. After having identified the foetal head as the structure that can potentially undergo important damages during childbirth, we present a model of the foetal head based on shell finite elements CST-DKT that we extend to a co-rotationnal formulation and a volume constraint allowing to take in count the intra-cranial matter. A GPU implementation of this model is also porposed to allow interactive simulations. This model is validated on a simulation of intra-uterine pressure undergone by the foetal head during the second phase of childbirth. Finally, we propose a draft of a complete model intended to simulate interactively the feotal descent

Shell finite element model for interactive fetal head deformation during childbirth

International audienceIn this paper, we design a flat shell finite element model in order to simulate the fetal head deformation during childbirth. This new method also guarantees the incompressibility of the fetal head enclosed volume

Biomechanical model of the fetal head for interactive childbirth simulation

International audienceThe biomechanical model presented in this paper offers precise dynamic simulation of the fetal head molding in a reasonable computational time making it suitable for use with haptic training simulators. Nevertheless, it can be improved by considering anisotropic material for the cranial bones. In future work, we plan to use our model with more complex scenarios involving the fetal head such as forceps and vacuum delivery