In vivo mechanical response of thigh soft tissues under compression: A two-layer model allows an improved representation of the local tissue kinematics.

Biomechanical parameters have the potential to be used as physical markers for prevention and diagnosis. Finite Element Analysis (FEA) is a widely used tool to evaluate these parameters in vivo. However, the development of clinically relevant FEA requires personalisation of the geometry, boundary conditions, and constitutive parameters. This contribution focuses on the characterisation of mechanical properties in vivo which remains a significant challenge for the community. The aim of this retrospective study is to evaluate the sensitivity of the computed elastic parameters (shear modulus of fat and muscle tissues) derived by inverse analysis as a function of the geometrical modelling assumption (homogenised monolayer vs bilayer) and the formulation of the cost function. The methodology presented here proposes to extract the experimental force-displacement response for each tissue layer (muscle and fat) and construct the associated Finite Element Model for each volunteer, based on data previously collected in our group (N = 7 volunteers) as reported in (Fougeron et al., 2020). The sensitivity analysis indicates that the choice of the cost function has minimal impact on the topology of the response surface in the parametric space. Each surface displays a valley of parameters that minimises the cost function. The constitutive properties of the thigh (reported as median ± interquartile range) were determined to be (µ=198±322Pa,α=37) for the monolayer and (µmuscle=1675±1127Pa,αmuscle=22±14,µfat=537±1131Pa,αfat=32±7) for the bilayer. A comparison of the homogenised monolayer and bilayer models showed that adding a layer reduces the error on the local force displacement curves, increasing the accuracy of the local kinematics of soft tissues during indentation. This allows for an increased understanding of load transmission in soft tissue. The comparison of the two models in terms of strains indicates that the modelling choice significantly influences the localization of maximal compressive strains. These results support the idea that the biomechanical community should conduct further work to develop reliable methodologies for estimating in vivo strain in soft tissue.

Comparison of telerobotic and conventional ultrasonography in children: a crossover bicentric pilot study.

Background: The MELODY system allows for performing ultrasonography on a patient remotely and has been proposed to assess disease characteristics in the context of the coronavirus disease 2019 (COVID-19) pandemic. The aim of this interventional crossover study was to address the feasibility of the system in children aged 1 to 10 years old. Methods: Children underwent ultrasonography with a telerobotic ultrasound system followed by a second conventional examination by a different sonographer. Results: In total, 38 children were enrolled, and 76 examinations were performed, with 76 scans analyzed. The mean [standard deviation (SD)] age of participants was 5.7 (2.7) years (range, 1-10 years). We found substantial agreement between telerobotic and conventional ultrasonography [κ=0.74 (95% CI: 0.53-0.94), P<0.005]. The mean (SD) duration was longer for telerobotic than conventional examinations [26.0 (2.5) vs. 13.9 (11.2) min, P<0.0001]. Abdominal organs and abnormalities were similarly visualized on telerobotic and conventional ultrasonography. Cardiac echocardiography provided reliable diagnoses, with non-significantly different measurements with both techniques, although the visualization score was significantly higher with conventional than telerobotic ultrasonography (P<0.05). On lung analysis, both examinations identified consolidations and pleural effusion, whereas visualization and total lung score were similar with the 2 techniques. Overall, 45% of parents reported that their children felt less pressure with the telerobotic system. Conclusions: Telerobotic ultrasonography may be effective, feasible, and well-tolerated in children.

High-resolution ultrasound and speckle tracking: a non-invasive approach to assess in vivo gastrointestinal motility during development.

Gastrointestinal motor activity has been extensively studied in adults; however, only few studies have investigated fetal motor skills. It is unknown when the gastrointestinal tract starts to contract during the embryonic period and how this function evolves during development. Here, we adapted a non-invasive high-resolution echography technique combined with speckle tracking analysis to examine the gastrointestinal tract motor activity dynamics during chick embryo development. We provided the first recordings of fetal gastrointestinal motility in living embryos without anesthesia. We found that, although gastrointestinal contractions appear very early during development, they become synchronized only at the end of the fetal period. To validate this approach, we used various pharmacological inhibitors and BAPX1 gene overexpression in vivo. We found that the enteric nervous system determines the onset of the synchronized contractions in the stomach. Moreover, alteration of smooth muscle fiber organization led to an impairment of this functional activity. Altogether, our findings show that non-invasive high-resolution echography and speckle tracking analysis allows visualization and quantification of gastrointestinal motility during development and highlight the progressive acquisition of functional and coordinated gastrointestinal motility before birth.

Pancreatic mucinous cystic tumor in Turner syndrome: How a tumor bends to a genetic disease.

INTRODUCTION: Mucinous cystic neoplasms (MCN) are uncommon tumors of the pancreatic corpus/tail occurring mostly in middle-aged women, with a variable clinico-biological behavior. On histology, MCNs concurrently show an epithelial mucosecreting component with ovarian-type stromal cells. PRESENTATION OF CASE: This report describes the first case of a pancreatic MCN with no ovarian-type stroma in a patient with Turner syndrome (TS). DISCUSSION: The mesenchymal component of MCN presumably results from the intra-pancreatic entrapment of ovarian stroma during embryogenesis. In our case, the absence of such stromal component may relate to the "dysgenetic" changes in the ovary involved in TS. CONCLUSION: The present case of primary pancreatic MCN arising in a TS-patient triggers some original speculation on the morphogenesis of pancreatic MCN, also expanding the current clinico-pathological knowledge of this extremely rare entity.

Unusual protrusion of conjunctiva in two neonates with harlequin ichthyosis.

BACKGROUND: We present two patients who developed severe protrusion of the conjunctiva and chemosis secondary to Harlequin ichthyosis (HI). CASE REPORTS: Case 1 was a male infant diagnosed with HI who had parchment-like appearance and conjunctival protrusion with severe chemosis. Case 2 was a female infant on whom HI had been suspected before birth through ultrasonography. She showed thickened skin over the entire body and conjunctival protrusion with severe chemosis. For both cases, a vitamin A derivative was applied and the hyperkeratotic layer was peeled off every day. Great care was taken to sterilize and moisten the ocular surface. The conjunctival protrusion gradually improved and other systemic conditions were successfully treated. HI is a rare condition, but affected infants are surviving longer than previously and hence guidelines for ocular management are now required. CONCLUSIONS: Gentle and patient debridement of the hyperkeratotic skin and moisturizing were important in treating the unusual conjunctival protrusion.