DentalSegmentator: Robust open source deep learning-based CT and CBCT image segmentation.

OBJECTIVES: Segmentation of anatomical structures on dento-maxillo-facial (DMF) computed tomography (CT) or cone beam computed tomography (CBCT) scans is increasingly needed in digital dentistry. The main aim of this research was to propose and evaluate a novel open source tool called DentalSegmentator for fully automatic segmentation of five anatomical structures on DMF CT and CBCT scans: maxilla/upper skull, mandible, upper teeth, lower teeth, and the mandibular canal. METHODS: A retrospective sample of 470 CT and CBCT scans was used as a training/validation set. The performance and generalizability of the tool was evaluated by comparing segmentations provided by experts and automatic segmentations in two hold-out test datasets: an internal dataset of 133 CT and CBCT scans acquired before orthognathic surgery and an external dataset of 123 CBCT scans randomly sampled from routine examinations in 5 institutions. RESULTS: The mean overall results in the internal test dataset (n = 133) were a Dice similarity coefficient (DSC) of 92.2 ± 6.3 % and a normalised surface distance (NSD) of 98.2 ± 2.2 %. The mean overall results on the external test dataset (n = 123) were a DSC of 94.2 ± 7.4 % and a NSD of 98.4 ± 3.6 %. CONCLUSIONS: The results obtained from this highly diverse dataset demonstrate that this tool can provide fully automatic and robust multiclass segmentation for DMF CT and CBCT scans. To encourage the clinical deployment of DentalSegmentator, the pre-trained nnU-Net model has been made publicly available along with an extension for the 3D Slicer software. CLINICAL SIGNIFICANCE: DentalSegmentator open source 3D Slicer extension provides a free, robust, and easy-to-use approach to obtaining patient-specific three-dimensional models from CT and CBCT scans. These models serve various purposes in a digital dentistry workflow, such as visualization, treatment planning, intervention, and follow-up.

Cardiovascular Fitness and Stride Acceleration in Race-Pace Workouts for the Prediction of Performance in Thoroughbreds.

In-training racehorse physiological data can be leveraged to further explore race-day performance prediction. To date, no large retrospective, observational study has analysed whether in-training speed and heart rate recovery can predict racehorse success. Speed (categorised as 'slow' to 'fast' according to the time taken to cover the last 600 m from a virtual finish line) and heart rate recovery (from gallop to 1 min after exercise) of flat racehorses (n = 485) of varying age, sex and type according to distance (e.g., sprinter, miler and stayer) were obtained using a fitness tracker from a single racing yard in Australia. Race-pace training sessions on turf comprised 'fast gallop' (n = 3418 sessions) or 'jumpout' (n = 1419). A posteriori racing information (n = 3810 races) for all 485 racehorses was extracted and combined with training data. Race performance was categorised as win/not-win or podium or not, each analysed by logistic regression. Colts (p < 0.001), stayers (p < 0.001) and being relatively fast over the last 600 m of a benchmark test in training (p < 0.008) were all predictive of race performance. Heart rate recovery after exercise (p = 0.21) and speed recorded at 600 m of a 1 km benchmark test in training (p = 0.94) were not predictive. In-training physiological data analytics used along with subjective experience may help trainers identify promising horses and improve decision-making.

Mechanical characterization of soft-tissue stiffness during mandibular distraction.

The purpose of this study was to determine the stiffness of mandibular soft tissues during mandibular distraction, from the perspective of improving distraction devices such as automated continuous distractors. Uncompleted osteotomy was performed on 11 fresh human hemimandibles via a greenstick fracture, to preserve the uplift of the internal periosteum of the mandibular corpus. In order to replicate continuous distraction, direct measurements were performed through a uniaxial quasi-static tensile test. For all specimens, linear regression was applied to the force-displacement curve for a force region of 10-20 N, and the slope extracted. The mean stiffness was estimated to be 9.12 ± 3.56 N/mm. This study is the first to measure directly the stiffness of the surrounding tissues of the human mandibular corpus, and paves the way to the design of a new generation of distractor devices.

[Improving the accuracy of the preoperative planning of mandibular osteogenic distraction by an external custom-made device]. / Optimisation du transfert de planification de la distraction ostéogénique mandibulaire par dispositif externe sur mesure.

PURPOSE: The aim of this study was to analyze the predictability of virtual surgical planning of mandibular reconstruction by osteogenic distraction (OD) with a custom-made osteogenic distraction device (DEOS) after ballistic trauma and to make recommendations to mitigate potential sources of discrepancy. METHODS: This retrospective study involved 12 patients who were victims of facial mandibular ballistic trauma and were reconstructed with osteogenic distraction with a DEOS device. Postoperative images were compared to the planned situation by means of several measures made in two plans : distraction plane and frontal plane. RESULTS: The mean bone loss was 54.2mm. The anteroposterior difference was systematically inferior or equal postoperatively (10.8mm). The interrami angle difference in the frontal plane was positive, with an average of 4.8°. There was a significant negative correlation in univariate analysis between the antero-posterior difference measurement and the difference of the interrami angle in distraction. CONCLUSION: A significant difference between the planning and postoperative results was shown, explained by the device being too adjustable leading to the loosening of the locking screws of the device. A static analysis showed that there are significant rotational forces at the carriages, which can lead to the loosening of the locking elements. It is then proposed that the device be optimized by customization of some elements.

Locomotory Profiles in Thoroughbreds: Peak Stride Length and Frequency in Training and Association with Race Outcomes.

Racehorses competing in short (i.e., 'sprinters'), middle- or longer-distance (i.e., 'stayers') flat races are assumed to have natural variation in locomotion; sprinters having an innately shorter stride than stayers. No study has objectively tested this theory. Here, racehorses (n = 421) were categorised as sprinters, milers or stayers based on known race distance (n = 3269 races). Stride parameters (peak length and frequency) of those racehorses were collected from prior race-pace training sessions on turf (n = 2689; 'jumpout', n = 1013), using a locomotion monitoring device. Pedigree information for all 421 racehorses was extracted to three-generations. In training, sprinters had a shorter stride of higher frequency and covered consecutive furlongs faster than stayers (p < 0.001). Relatively short or longer stride did not predict race success, but stayers had greater race success than sprinters (p < 0.001). Peak stride length and frequency were moderately heritable (h2 = 0.15 and 0.20, respectively). In conclusion, differences in stride were apparent between sprinters and stayers (e.g., shorter stride in sprinters) during routine training, even after accounting for their pedigree. Objective data on stride characteristics could supplement other less objectively obtained parameters to benefit trainers in the appropriate selection of races for each individual racehorse.

Does sex of the jockey influence racehorse physiology and performance.

The racing industry is supported by a predominance of female stablehands and work riders, but few become professional jockeys. Female jockeys have recently had notable race success. No study has assessed whether the sex of the rider may subtly influence racehorse physiology to affect performance. Here, using a validated exercise tracking system (the 'Equimetre'™) that records many physiological parameters simultaneously, this study characterised racehorse cardiovascular (heart rate, heart rate recovery) and biomechanical (stride length and frequency) parameters at various exercise intensities (slow canter to hard gallop) to address the question whether any parameter varied according to sex of the rider. A total of 530 Thoroughbreds, varying in age (2-7 years old) and sex (including geldings), from one racing yard in Australia, completed a total of 3,568 exercise sessions, monitored by a single trainer, on varying track surfaces (sand, turf, or fibre). Different work riders,103 in total (male, n = 66; female, n = 37) of which n = 43 were current or past registered professional jockeys, participated in the study. Data were analysed using analysis of variation (ANOVA) or mixed-effect models, as appropriate. Sex of the rider did not influence (P > 0.05) racehorse speed nor stride length at any training intensity. Racehorse heart rate and peak heart rate increased with training intensity (P < .001), with no difference according to sex of rider (P > 0.05). Racehorse heart rate recovery was influenced by sex of the rider, but only at the extremes of the reversed, usual training intensity on each surface (e.g. heart rate after galloping on sand was significantly lower with male riders, P = 0.03). Finally, analysis of 52,464 race results indicated a similar chance of a top-three placing for male and female jockeys. In conclusion, this study, using objectively obtained data, demonstrates for the first time no overt effect of the rider's sex on racehorse physiology in training and performance in racing. Such data could encourage greater female participation in racing and improve access of female jockeys to better quality mounts in racing events.

Repeated-Dose Toxicity, Biodistribution, and Shedding Assessments With a ChAd155 Respiratory Syncytial Virus Vaccine Candidate Evaluated in Rabbits and Rats.

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections (LRTI) in infants, and toddlers and vaccines are not yet available. A pediatric RSV vaccine (ChAd155-RSV) is being developed to protect infants against RSV disease. The ChAd155-RSV vaccine consists of a recombinant replication-deficient chimpanzee-derived adenovirus (ChAd) group C vector engineered to express the RSV antigens F, N, and M2-1. The local and systemic effects of three bi-weekly intramuscular injections of the ChAd155-RSV vaccine was tested in a repeated-dose toxicity study in rabbits. After three intramuscular doses, the ChAd155-RSV vaccine was considered well-tolerated. Changes due to the vaccine-elicited inflammatory reaction/immune response were observed along with transient decreases in platelet count without physiological consequences, already reported for other adenovirus-based vaccines. In addition, the biodistribution and shedding of ChAd155-RSV were also characterized in two studies in rats. The distribution and persistence of the ChAd155-RSV vaccine candidate was consistent with other similar adenovector-based vaccines, with quantifiable levels of ChAd155-RSV observed at the injection site (muscle) and the draining lymph nodes up to 69 days post administration. The shedding results demonstrated that ChAd155-RSV was generally not detectable in any secretions or excreta samples. In conclusion, the ChAd155-RSV vaccine was well-tolerated locally and systemically.

Validation of an equine fitness tracker: ECG quality and arrhythmia detection.

BACKGROUND: Cardiac arrhythmias in exercising horses are the focus of much interest, both in terms of what is considered normal and potential associations with poor performance and sudden cardiac death. One barrier to performing large-scale studies is the lack of an easily applicable device, to allow recording of large numbers of high-quality exercising electrocardiograms (ECGs). The EquimetreTM is a new wearable device which records a single lead ECG, amongst other parameters. Validation of such wearable devices is essential before further studies are undertaken. OBJECTIVES: To evaluate the quality of ECG using the EquimetreTM and compare arrhythmia detection during exercise with the reference TelevetTM system. STUDY DESIGN: Prospective blinded clinical study. METHODS: Simultaneous ECGs were recorded with both systems in 49 healthy horses during exercise. High intensity exercise (>40km/h) was performed by 29 racehorses, and lower intensity exercise for the remainder of the racehorses and show jumpers. Tracings were excluded if >10% artefact was present (duration of artefact relative to duration of exercise). For included ECGs, the duration of artefact was recorded and compared. ECGs were evaluated using Kubios premium software. Arrhythmia detection (yes/no) and arrhythmia classification (sinus arrhythmia, narrow complex of similar morphology to the sinus complexes or wide complex with a different morphology) were compared using Cohen's Kappa coefficient. RESULTS: Nine TelevetTM ECGs and 3 EquimetreTM ECGs were excluded due to artefact >10%. TelevetTM ECGs included significantly more artefact during exercise than EquimetreTM ECGs (5% vs. 0.25% p<0.001). Arrhythmia analysis was performed on 38 horses' paired ECGs. The Kappa coefficient was excellent for arrhythmia detection (K=0.97) and arrhythmia classification (K=0.93). MAIN LIMITATIONS: Relatively low numbers of horses with arrhythmias (n=21) were included. The ECG recordings only provided one lead, making arrhythmia classification challenging in some cases. CONCLUSIONS: The Equimetre device provides a reliable ECG for arrhythmia detection during exercise. This system may be useful clinically and for future large-scale investigations into the occurrence and significance of exercising arrhythmias.

Fully automatic segmentation of craniomaxillofacial CT scans for computer-assisted orthognathic surgery planning using the nnU-Net framework.

OBJECTIVES: To evaluate the performance of the nnU-Net open-source deep learning framework for automatic multi-task segmentation of craniomaxillofacial (CMF) structures in CT scans obtained for computer-assisted orthognathic surgery. METHODS: Four hundred and fifty-three consecutive patients having undergone high-resolution CT scans before orthognathic surgery were randomly distributed among a training/validation cohort (n = 300) and a testing cohort (n = 153). The ground truth segmentations were generated by 2 operators following an industry-certified procedure for use in computer-assisted surgical planning and personalized implant manufacturing. Model performance was assessed by comparing model predictions with ground truth segmentations. Examination of 45 CT scans by an industry expert provided additional evaluation. The model's generalizability was tested on a publicly available dataset of 10 CT scans with ground truth segmentation of the mandible. RESULTS: In the test cohort, mean volumetric Dice similarity coefficient (vDSC) and surface Dice similarity coefficient at 1 mm (sDSC) were 0.96 and 0.97 for the upper skull, 0.94 and 0.98 for the mandible, 0.95 and 0.99 for the upper teeth, 0.94 and 0.99 for the lower teeth, and 0.82 and 0.98 for the mandibular canal. Industry expert segmentation approval rates were 93% for the mandible, 89% for the mandibular canal, 82% for the upper skull, 69% for the upper teeth, and 58% for the lower teeth. CONCLUSION: While additional efforts are required for the segmentation of dental apices, our results demonstrated the model's reliability in terms of fully automatic segmentation of preoperative orthognathic CT scans. KEY POINTS: • The nnU-Net deep learning framework can be trained out-of-the-box to provide robust fully automatic multi-task segmentation of CT scans performed for computer-assisted orthognathic surgery planning. • The clinical viability of the trained nnU-Net model is shown on a challenging test dataset of 153 CT scans randomly selected from clinical practice, showing metallic artifacts and diverse anatomical deformities. • Commonly used biomedical segmentation evaluation metrics (volumetric and surface Dice similarity coefficient) do not always match industry expert evaluation in the case of more demanding clinical applications.

Ultrasound shearwave elastography to characterize muscles of healthy and cerebral palsy children.

Shear wave elastography (SWE) is an ultrasound technique to obtain soft tissue mechanical properties. The aim of this study was to establish the reliability of SWE in young children, define reference data on healthy ones and compare the shear modulus of healthy and spastic muscles from cerebral palsy (CP). The reproducibility is evaluated: at rest, on 7 children without any musculoskeletal pathology by 3 different operators, on 2 muscles: biceps brachii long head and medial gastrocnemius. The comparison study was made, on the same 2 muscles, at rest and under passive stretching, with a control group (29 healthy children), a spastic group (spastic muscles of 16 children from CP) and a non-spastic group (non-spastic muscles of 14 children from CP). The intra-operator reliability and inter-operator reliability, in terms of standard deviation, were 0.6 kPa (11.2% coefficient of variation (CV)) and 0.8 kPa (14.9% CV) for the biceps, respectively, and 0.4 kPa (11.5% CV) and 0.5 kPa (13.8% CV) for the gastrocnemius. At rest, no significant difference was found. Under passive stretching, the non-spastic CP biceps were significantly stiffer than the control ones (p = 0.033). Spastic gastrocnemius had a higher shear modulus than in the control muscles (p = 0.0003) or the non-spastic CP muscles (p = 0.017). CP stretched medial gastrocnemius presented an abnormally high shear moduli for 50% of patients.

Nonclinical safety assessment of repeated administration and biodistribution of a novel rabies self-amplifying mRNA vaccine in rats.

The novel self-amplifying mRNA (SAM) technology for vaccines consists of an engineered replication-deficient alphavirus genome encoding an RNA-dependent RNA polymerase and the gene of the target antigen. To validate the concept, the rabies glycoprotein G was chosen as antigen. The delivery system for this vaccine was a cationic nanoemulsion. To characterize the local tolerance, potential systemic toxicity and biodistribution of this vaccine, two nonclinical studies were performed. In the repeated dose toxicity study, the SAM vaccine was administered intramuscularly to rats on four occasions at two-week intervals followed by a four-week recovery period. SAM-related changes consisted of a transient increase in neutrophil count, alpha-2-macroglobulin and fibrinogen levels. Transient aspartate aminotransferase and alanine aminotransferase increases were also noted in females only. At necropsy, observations related to the elicited inflammatory reaction, such as enlargement of the draining lymph nodes were observed that were almost fully reversible by the end of the recovery period. In the biodistribution study, rats received a single intramuscular injection of SAM vaccine and then were followed until Day 60. Rabies RNA was found at the injection sites and in the draining lymph nodes one day after administration, then generally decreased in these tissues but remained detectable up to Day 60. Rabies RNA was also transiently found in blood, lungs, spleen and liver. No microscopic changes in the brain and spinal cord were recorded. In conclusion, these results showed that the rabies SAM vaccine was well-tolerated by the animals and supported the clinical development program.

Muscle Shear Wave Elastography in Inclusion Body Myositis: Feasibility, Reliability and Relationships with Muscle Impairments.

Degenerative muscle changes may be associated with changes in muscle mechanical properties. Shear wave elastography (SWE) allows direct quantification of muscle shear modulus (MSM). The aim of this study was to evaluate the feasibility and reliability of SWE in the severely disordered muscle as observed in inclusion body myositis. To explore the clinical relevance of SWE, potential relationships between MSM values and level muscle impairments (weakness and ultrasound-derived muscle thickness and echo intensity) were investigated. SWE was performed in the biceps brachii at 100°, 90°, 70° and 10° elbow flexion in 34 patients with inclusion body myositis. MSM was assessed before and after five passive stretch-shortening cycles at 4°/s from 70° to 10° elbow angle and after three maximal voluntary contractions to evaluate potential effects of muscle pre-conditioning. Intra-class correlation coefficients and standard errors of measurements were >0.83 and <1.74 kPa and >0.64 and <1.89 kPa for within- and between-day values, respectively. No significant effect of passive loading-unloading and maximal voluntary contractions was found (all p values >0.18). MSM correlated to predicted muscle strength (all Spearman correlation coefficients (ρ) > 0.36; all p values < 0.05). A significant correlation was found between muscle echo intensity and muscle shear modulus at 70° only (ρ = 0.38, p <0.05). No correlation was found between muscle thickness and MSM (all ρ values > 0.23 and all p values > 0.25, respectively). Within- and between-day reliability of muscle SWE was satisfactory and moderate, respectively. SWE shows promise for assessing changes in mechanical properties of the severely disordered muscle. Further investigations are required to clarify these findings and to refine their clinical value.

Local Texture Anisotropy as an Estimate of Muscle Quality in Ultrasound Imaging.

This study introduces local pattern texture anisotropy as a novel parameter to differentiate healthy and disordered muscle and to gauge the severity of muscle impairments based on B-mode ultrasound images. Preliminary human results are also presented. A local pattern texture anisotropy index (TAI) was computed in one region of interest in the short head of the biceps brachii. The effects of gain settings and box sizes required for TAI computation were investigated. Between-day reliability was studied in patients with sporadic inclusion body myositis (n = 26). The ability of the TAI to discriminate dystrophic from healthy muscle was evaluated in patients with Duchenne muscular dystrophy and healthy controls (n = 16). TAI values were compared with a gray-scale index (GSI). TAI values were less influenced by gain settings than were GSI values. TAI had lower between-day variability (typical error = 2.3%) compared with GSI (typical error = 2.3% vs. 8.3%, respectively). Patients with Duchenne muscular dystrophy had lower TAIs than controls (0.76 ± 0.06 vs. 0.87 ± 0.03, respectively, p <0.05). At 40% gain, TAI values correlated with percentage predicted elbow flexor strength in inclusion body myositis (R = 0.63, p <0.001). The TAI may be a promising addition to other texture-based approaches for quantitative muscle ultrasound imaging.

The OC43 human coronavirus envelope protein is critical for infectious virus production and propagation in neuronal cells and is a determinant of neurovirulence and CNS pathology.

The OC43 strain of human coronavirus (HCoV-OC43) is an ubiquitous respiratory tract pathogen possessing neurotropic capacities. Coronavirus structural envelope (E) protein possesses specific motifs involved in protein-protein interaction or in homo-oligomeric ion channel formation, which are known to play various roles including in virion morphology/assembly and in cell response to infection and/or virulence. Making use of recombinant viruses either devoid of the E protein or harboring mutations either in putative transmembrane domain or PDZ-binding motif, we demonstrated that a fully functional HCoV-OC43 E protein is first needed for optimal production of recombinant infectious viruses. Furthermore, HCoV-OC43 infection of human epithelial and neuronal cell lines, of mixed murine primary cultures from the central nervous system and of mouse central nervous system showed that the E protein is critical for efficient and optimal virus replication and propagation, and thereby for neurovirulence.

Comparative finite element analysis of skull mechanical properties following parietal bone graft harvesting in adults.

INTRODUCTION: Parietal bone grafts are commonly used in cranio-maxillo-facial surgery. Both the outer and the internal layer of the calvarium can be harvested. The bone defect created by this harvesting may induce significant weakening of the skull that has not been extensively evaluated. Our aim was to evaluate the consequences of parietal bone graft harvesting on mechanical properties of the skull using a finite element analysis. METHODS: Finite elements models of the skull of 3 adult patients were created from CT scans. Parietal external and internal layer harvest models were created. Frontal, lateral, and parietal loading were modeled and von Mises stress distributions were compared. RESULTS: The maximal von Mises stress was higher for models of bone harvesting, both on the whole skull and at the harvested site. Maximal von Mises stress was even higher for models with internal layer defect. CONCLUSIONS: Harvesting parietal bone modifies the skull's mechanical strength and can increase the risk of skull fracture, mainly on the harvested site. Outer layer parietal graft harvesting is indicated. Graft harvesting located in the upper part of the parietal bone, close to the sagittal suture and with smooth internal edges and corners should limit the risk of fracture.

Bezafibrate Improves Insulin Sensitivity and Metabolic Flexibility in STZ-Induced Diabetic Mice.

Bezafibrate (BEZ), a pan activator of peroxisome proliferator-activated receptors (PPARs), has been generally used to treat hyperlipidemia for decades. Clinical trials with type 2 diabetes patients indicated that BEZ also has beneficial effects on glucose metabolism, although the underlying mechanisms of these effects remain elusive. Even less is known about a potential role for BEZ in treating type 1 diabetes. Here we show that BEZ markedly improves hyperglycemia and glucose and insulin tolerance in mice with streptozotocin (STZ)-induced diabetes, an insulin-deficient mouse model of type 1 diabetes. BEZ treatment of STZ mice significantly suppressed the hepatic expression of genes that are annotated in inflammatory processes, whereas the expression of PPAR and insulin target gene transcripts was increased. Furthermore, BEZ-treated mice also exhibited improved metabolic flexibility as well as an enhanced mitochondrial mass and function in the liver. Finally, we show that the number of pancreatic islets and the area of insulin-positive cells tended to be higher in BEZ-treated mice. Our data suggest that BEZ may improve impaired glucose metabolism by augmenting hepatic mitochondrial performance, suppressing hepatic inflammatory pathways, and improving insulin sensitivity and metabolic flexibility. Thus, BEZ treatment might also be useful for patients with impaired glucose tolerance or diabetes.

Lumbar annulus fibrosus biomechanical characterization in healthy children by ultrasound shear wave elastography.

OBJECTIVES: Intervertebral disc (IVD) is key to spine biomechanics, and it is often involved in the cascade leading to spinal deformities such as idiopathic scoliosis, especially during the growth spurt. Recent progress in elastography techniques allows access to non-invasive measurement of cervical IVD in adults; the aim of this study was to determine the feasibility and reliability of shear wave elastography in healthy children lumbar IVD. METHODS: Elastography measurements were performed in 31 healthy children (6-17 years old), in the annulus fibrosus and in the transverse plane of L5-S1 or L4-L5 IVD. Reliability was determined by three experienced operators repeating measurements. RESULTS: Average shear wave speed in IVD was 2.9 ± 0.5 m/s; no significant correlations were observed with sex, age or body morphology. Intra-operator repeatability was 5.0 % while inter-operator reproducibility was 6.2 %. Intraclass correlation coefficient was higher than 0.9 for each operator. CONCLUSIONS: Feasibility and reliability of IVD shear wave elastography were demonstrated. The measurement protocol is compatible with clinical routine and the results show the method's potential to give an insight into spine deformity progression and early detection. KEY POINTS: • Intervertebral disc mechanical properties are key to spine biomechanics • Feasibility of shear wave elastography in children lumbar disc was assessed • Measurement was fast and reliable • Elastography could represent a novel biomarker for spine pathologies.

Reliable protocol for shear wave elastography of lower limb muscles at rest and during passive stretching.

Development of shear wave elastography gave access to non-invasive muscle stiffness assessment in vivo. The aim of the present study was to define a measurement protocol to be used in clinical routine for quantifying the shear modulus of lower limb muscles. Four positions were defined to evaluate shear modulus in 10 healthy subjects: parallel to the fibers, in the anterior and posterior aspects of the lower limb, at rest and during passive stretching. Reliability was first evaluated on two muscles by three operators; these measurements were repeated six times. Then, measurement reliability was compared in 11 muscles by two operators; these measurements were repeated three times. Reproducibility of shear modulus was 0.48 kPa and repeatability was 0.41 kPa, with all muscles pooled. Position did not significantly influence reliability. Shear wave elastography appeared to be an appropriate and reliable tool to evaluate the shear modulus of lower limb muscles with the proposed protocol.

Three-dimensional parabolic equation model for low frequency sound propagation in irregular urban canyons.

A three-dimensional wide-angle parabolic equation (3DPE) is used to model low frequency sound propagation in irregular urban canyons at low computational cost. This one-way wave equation is solved using the Alternating Direction Implicit method. A finite difference scheme adapted to the geometry of the urban environment is then developed. Abrupt variations of the street width are treated as a single scattering problem using the Kirchhoff approximation. Numerical results are compared with experimental data obtained on a scale model of a street. Comparisons show the ability of the 3DPE model to provide reliable transmitted fields even for large irregularities.

Non-invasive biomechanical characterization of intervertebral discs by shear wave ultrasound elastography: a feasibility study.

OBJECTIVES: Although magnetic resonance is widely spread to assess qualitatively disc morphology, a simple method to determine reliably intervertebral disc status is still lacking. Shear wave elastography is a novel technique that allows quantitative evaluation of soft-tissues' mechanical properties. The aim of this study was to assess preliminary the feasibility and reliability of mechanical characterization of cervical intervertebral discs by elastography and to provide first reference values for asymptomatic subjects. METHODS: Elastographic measurements were performed to determine shear wave speed (SWS) in C6-C7 or C7-T1 disc of 47 subjects; repeatability and inter-operator reproducibility were assessed. RESULTS: Global average shear wave speed (SWS) was 3.0 ± 0.4 m/s; measurement repeatability and inter-user reproducibility were 7 and 10%, respectively. SWS was correlated with both subject's age (p = 1.3 × 10(-5)) and body mass index (p = 0.008). CONCLUSIONS: Shear wave elastography in intervertebral discs proved reliable and allowed stratification of subjects according to age and BMI. Applications could be relevant, for instance, in early detection of disc degeneration or in follow-up after trauma; these results open the way to larger cohort studies to define the place of this technique in routine intervertebral disc assessment. KEY POINTS: A simple method to obtain objectively intervertebral disc status is still lacking. Shear wave elastography was applied in vivo to assess intervertebral discs. Elastography showed promising results in biomechanical disc evaluation. Elastography could be relevant in clinical routine for intervertebral disc assessment.