Prediction of Rotator Cuff Muscle Fibre Orientations Using a Population-Averaged Atlas Generated With Anatomical and Diffusion-Weighted Magnetic Resonance Images.

Measurements of muscle architecture are crucial for understanding muscle function but are often difficult to obtain in human muscles in vivo. This study aimed to create population-averaged atlases of human rotator cuff muscle shape and muscle fibre orientations from anatomical magnetic resonance images (MRI) and diffusion-weighted images (DWI) and to utilise these atlases to predict muscle fibre orientations from anatomical MRI data alone. An image registration framework was applied to coregister anatomical MRI and DWI data of 11 male and 9 female subjects into sex-specific common spaces, forming the basis for the atlases.

Ambulant children with cerebral palsy have similar leg muscle moment arms to typically developing children.

Many children with cerebral palsy (CP) have muscle contractures and bony deformities. It has been hypothesised that these musculoskeletal abnormalities could increase or decrease muscle moment arms and cause movement dysfunction. In this study, we first investigated the relationship between skeletal growth (tibia length) and three-dimensional measurements of Achilles tendon and tibialis anterior moment arms from magnetic resonance images of 200 typically developing children aged 5 to 15 years.

Childhood muscle growth: Reference curves for lower leg muscle volumes and their clinical application in cerebral palsy.

Skeletal muscles grow substantially during childhood. However, quantitative information about the size of typically developing children's muscles is sparse. Here, the objective was to construct muscle-specific reference curves for lower leg muscle volumes in children aged 5 to 15 y.

How mandibular and hyoid morphology alters tongue muscle architecture in healthy adults: An anatomical atlas and statistical shape model of the tongue.

The tongue is a muscular hydrostat whose complex fibre architecture enables its diverse functions in swallowing, speech, and breathing. Current understanding of the tongue's structure is largely based on ex vivo dissections, which are not directly linked to function. This study aimed to develop an anatomical atlas of the living human tongue incorporating detailed muscle architecture.

A mechanically consistent muscle model shows that the maximum force-generating capacity of muscles is influenced by optimal fascicle length and muscle shape.

Muscle forces are difficult to measure in vivo, so the force-generating capacity of muscles is commonly inferred from muscle architecture. It is often assumed, implicitly or explicity, that a muscle's maximum force-generating capacity is proportional to physiological cross-sectional area (PCSA), and that a muscle's operating range is proportional to mean optimal fascicle length. Here, we examined the effect of muscle architecture (PCSA and fascicle length) on muscle function (maximal isometric force and operating range) using a three-dimensional finite element model which accounts in a mechanically consistent way for muscle deformation and other complexities of muscle contraction.

Improving cross-domain generalizability of medical image segmentation using uncertainty and shape-aware continual test-time domain adaptation.

Continual test-time adaptation (CTTA) aims to continuously adapt a source-trained model to a target domain with minimal performance loss while assuming no access to the source data. Typically, source models are trained with empirical risk minimization (ERM) and assumed to perform reasonably on the target domain to allow for further adaptation. However, ERM-trained models often fail to perform adequately on a severely drifted target domain, resulting in unsatisfactory adaptation results.

Three-dimensional architecture of the human subscapularis muscle in vivo.

Detailed analysis of skeletal muscle architecture provides insights into skeletal muscle function. To date, measurements of the human subscapularis architecture have been limited to cadaveric measurements. In this study we demonstrate the feasibility of using anatomically constrained fibre tractography to reconstruct and quantify the 3D architecture of the human subscapularis muscle, and provide the first quantitative measurements of the architecture of the human subscapularis muscle in vivo.

Three-dimensional architecture and moment arms of human rotator cuff muscles in vivo: Interindividual, intermuscular, and intramuscular variations.

The human rotator cuff consists of four muscles, each with a complex, multipennate architecture. Despite the functional and clinical importance, the architecture of the human rotator cuff has yet to be clearly described in humans in vivo. The purpose of this study was to investigate the intramuscular, intermuscular, and interindividual variations in architecture and moment arms of the human rotator cuff.

Hybrid dual mean-teacher network with double-uncertainty guidance for semi-supervised segmentation of magnetic resonance images.

Semi-supervised learning has made significant progress in medical image segmentation. However, existing methods primarily utilize information from a single dimensionality, resulting in sub-optimal performance on challenging magnetic resonance imaging (MRI) data with multiple segmentation objects and anisotropic resolution. To address this issue, we present a Hybrid Dual Mean-Teacher (HD-Teacher) model with hybrid, semi-supervised, and multi-task learning to achieve effective semi-supervised segmentation.

Compositional and Functional MRI of Skeletal Muscle: A Review.

Due to its exceptional sensitivity to soft tissues, MRI has been extensively utilized to assess anatomical muscle parameters such as muscle volume and cross-sectional area. Quantitative Magnetic Resonance Imaging (qMRI) adds to the capabilities of MRI, by providing information on muscle composition such as fat content, water content, microstructure, hypertrophy, atrophy, as well as muscle architecture. In addition to compositional changes, qMRI can also be used to assess function for example by measuring muscle quality or through characterization of muscle deformation during passive lengthening/shortening and active contractions.

Three-dimensional skeletal muscle architecture in the lower legs of living human infants.

Little is known about the skeletal muscle architecture of living humans at birth. In this study, we used magnetic resonance imaging (MRI) to measure the volumes of ten muscle groups in the lower legs of eight human infants aged less than three months. We then combined MRI and diffusion tensor imaging (DTI) to provide detailed, high-resolution reconstructions and measurements of moment arms, fascicle lengths, physiological cross-sectional areas (PCSAs), pennation angles and diffusion parameters of the medial (MG) and lateral gastrocnemius (LG) muscles.

Strain-dependent shear properties of human adipose tissue in vivo.

Introduction: Human adipose tissue (fat) deforms substantially under normal physiological loading and during impact. Thus, accurate data on strain-dependent stiffness of fat is essential for the creation of accurate biomechanical models. Previous studies on ex vivo samples reported human fat to be nonlinear and viscoelastic.

A new framework for analysis of three-dimensional shape and architecture of human skeletal muscles from in vivo imaging data.

A new framework is presented for comprehensive analysis of the three-dimensional shape and architecture of human skeletal muscles from magnetic resonance and diffusion tensor imaging data. The framework comprises three key features: ) identification of points on the surface of and inside a muscle that have a correspondence to points on and inside another muscle, ) reconstruction of average muscle shape and average muscle fiber orientations, and ) utilization of data on between-muscle variation to visualize and make statistical inferences about changes or differences in muscle shape and architecture. The general use of the framework is demonstrated by its application to three case studies.

Quantity versus quality: Age-related differences in muscle volume, intramuscular fat, and mechanical properties in the triceps surae.

With aging comes reductions in the quality and size of skeletal muscle. These changes influence the force-generating capacity of skeletal muscle and contribute to movement deficits that accompany aging. Although declines in strength remain a significant barrier to mobility in older adults, the association between age-related changes in muscle structure and function remain unresolved.

Deep learning methods for automatic segmentation of lower leg muscles and bones from MRI scans of children with and without cerebral palsy.

Cerebral palsy is a neurological condition that is known to affect muscle growth. Detailed investigations of muscle growth require segmentation of muscles from MRI scans, which is typically done manually. In this study, we evaluated the performance of 2D, 3D, and hybrid deep learning models for automatic segmentation of 11 lower leg muscles and two bones from MRI scans of children with and without cerebral palsy.

Regional variation in lateral and medial gastrocnemius muscle fibre lengths obtained from diffusion tensor imaging.

Assessment of regional muscle architecture is primarily done through the study of animals, human cadavers, or using b-mode ultrasound imaging. However, there remain several limitations to how well such measurements represent in vivo human whole muscle architecture. In this study, we developed an approach using diffusion tensor imaging and magnetic resonance imaging to quantify muscle fibre lengths in different muscle regions along a muscle's length and width.

Movement of the ribs in supine humans for small and large changes in lung volume.

An object-tracking algorithm was used on computed tomography (CT) images of the thorax from six healthy participants and nine participants with chronic obstructive pulmonary disease (COPD) to describe the movement of the ribs between the static lung volumes of functional residual capacity (FRC) and total lung capacity (TLC). The continuous motion of the ribs during tidal breathing was also described using four-dimensional CT datasets from seven participants with thoracic esophageal malignancies. Rib motion was defined relative to a local joint coordinate system where rotations about the axes that predominantly affected the anteroposterior and transverse diameters of the rib cage were referred to as pump-handle and bucket-handle movements, respectively.

MRI-based Measurement of Effects of Strength Training on Intramuscular Fat in People with and without Spinal Cord Injury.

Introduction: The accurate quantification of the proportion of fat in human muscles could help monitor disease status and test effectiveness of interventions in people with neurological conditions whose skeletal muscles are frequently infiltrated with fat.

Methods: We compared two commonly used magnetic resonance imaging methods to quantify fat in muscles. Measurements were obtained before and after 6 or 8 wk of strength training in a total of 116 muscles spanning the range of intramuscular fat proportions observed in able-bodied young adults and people with spinal cord injury.

Intramuscular fat in children with unilateral cerebral palsy.

Background: Many children with cerebral palsy develop muscle contractures. The mechanisms of contracture are not well understood. We investigated the possibility that, because fat is stiffer than passive muscle, elevated intramuscular fat contributes to contracture.

Intramuscular Fat in the Medial Gastrocnemius Muscle of People Who Have Had a Stroke.

To compare intramuscular fat fraction in people who have ankle contractures following stroke with the intramuscular fat fraction in control participants. mDixon MRI images were used to quantify intramuscular fat fractions in the medial gastrocnemius muscles of people who had experienced a hemiparetic stroke ( = 14, mean age 60 ± 13 years) and control participants ( = 18, mean age 66 ± 12 years). Intramuscular fat fractions were similar in the paretic and non-paretic sides of stroke patients (mean on paretic side 14.

Architecture of the medial gastrocnemius muscle in people who have had a stroke: A diffusion tensor imaging investigation.

Unlabelled: People who have had a stroke often develop ankle contractures which may be caused by changes in architecture of calf muscles. Anatomically constrained diffusion tensor imaging has recently been used to make three-dimensional, whole-muscle measurements of muscle architecture. Here, we compared the architecture of the medial gastrocnemius muscle in the paretic and non-paretic sides of people who have had a hemiparetic stroke and control participants using novel imaging techniques.

Muscle architecture in children with cerebral palsy and ankle contractures: an investigation using diffusion tensor imaging.

Background: Children with cerebral palsy frequently have ankle contractures which may be caused by changes in architecture of calf muscles. Here, we compared the architecture of medial gastrocnemius muscles in children with unilateral cerebral palsy and typically developing children using novel imaging techniques.

Methods And Procedures: Muscle volumes, fascicle lengths, pennation angles and physiological cross-sectional areas were measured from diffusion tensor images and mDixon scans obtained from 20 ambulant children with unilateral spastic cerebral palsy who had ankle contractures (age 11 ± 3 years; mean ± standard deviation) and 20 typically developing children (11 ± 4 years).