A computational approach to calculate personalized pennation angle based on MRI: effect on motion analysis.

Purpose: Muscles are the primary component responsible for the locomotion and change of posture of the human body. The physiologic basis of muscle force production and movement is determined by the muscle architecture (maximum muscle force, [Formula: see text], optimal muscle fiber length, [Formula: see text], tendon slack length, [Formula: see text], and pennation angle at optimal muscle fiber length, [Formula: see text]). The pennation angle is related to the maximum force production and to the range of motion.

Soft-tissue balance in short and straight stem total hip arthroplasty.

The growing numbers of short stem hip implants have redefined total hip arthroplasty with new stem geometries and possible functional differences. Several systematic reviews have reported good clinical results with this new class of stems, although kinematic alterations are still unclear in many aspects. The good clinical results obtained at the authors' institution led to the current study.

Skeletal muscle fascicle arrangements can be reconstructed using a Laplacian vector field simulation.

Skeletal muscles are characterized by a large diversity in anatomical architecture and function. Muscle force and contraction are generated by contractile fiber cells grouped in fascicle bundles, which transmit the mechanical action between origin and insertion attachments of the muscle. Therefore, an adequate representation of fascicle arrangements in computational models of skeletal muscles is important, especially when investigating three-dimensional muscle deformations in finite element models.

2-D strain assessment in the mouse through spatial compounding of myocardial velocity data: in vivo feasibility.

Ultrasound assessment of myocardial strain can provide valuable information on regional cardiac function. However, Doppler-based methods often used in practice for strain estimation suffer from angle dependency. In this study, a partial solution to that fundamental limitation is presented.

Comparison of conventional parallel beamforming with plane wave and diverging wave imaging for cardiac applications: a simulation study.

When imaging the heart, good temporal resolution is beneficial for capturing the information of short-lived cardiac phases (in particular, the isovolumetric phases). To increase the frame rate, parallel beamforming is a commonly used technique for fast cardiac imaging. Conventionally, a 4 multiple-line-acquisition (4MLA) system increases the frame rate by a factor of 4, making use of a broadened transmit beam to reduce block-like artifacts.

Regional cardiac motion and strain estimation in three-dimensional echocardiography: a validation study in thick-walled univentricular phantoms.

Automatic quantification of regional left ventricular deformation in volumetric ultrasound data remains challenging. Many methods have been proposed to extract myocardial motion, including techniques using block matching, phase-based correlation, differential optical flow methods, and image registration. Our lab previously presented an approach based on elastic registration of subsequent volumes using a B-spline representation of the underlying transformation field.

2D myocardial strain assessment in the mouse: a comparison between a synthetic lateral phase approach and block-matching using computer simulation.

Estimating myocardial strain in the mouse with clinical equipment remains difficult due to the high heart rate and the small size of the mouse heart. Measuring the strain component perpendicular to the ultrasound beam is especially challenging because of the lack of phase information in that direction and the large speckle width compared to the wall thickness. In this study, the performance of a Synthetic Lateral Phase (SLP) approach was contrasted to a standard and a regularized 2D Speckle Tracking (2D ST) algorithm using simulated data sets.

Left-ventricular shape determines intramyocardial mechanical heterogeneity.

Left-ventricular remodeling is considered to be an important mechanism of disease progression leading to mechanical dysfunction of the heart. However, the interaction between the physiological changes in the remodeling process and the associated mechanical dysfunction is still poorly understood. Clinically, it has been observed that the left ventricle often undergoes large shape changes, but the importance of left-ventricular shape as a contributing factor to alterations in mechanical function has not been clearly determined.

Burrowing and subsurface locomotion in anguilliform fish: behavioral specializations and mechanical constraints.

Fish swimming is probably one of the most studied and best understood locomotor behaviors in vertebrates. However, many fish also actively exploit sediments. Because of their elongate body shape, anguilliform fishes are not only efficient swimmers but also very maneuverable.

Kinematics of swimming in two burrowing anguilliform fishes.

Anguilliform or eel-like fishes are typically bottom dwellers, some of which are specialized burrowers. Although specializations for burrowing are predicted to affect the kinematics of swimming, it remains unknown to what extent this is actually the case. Here we examine swimming kinematics and efficiency of two burrowing anguilliform species, Pisodonophis boro and Heteroconger hassi, with different degrees of specialization for burrowing.

Distribution of active fiber stress at the beginning of ejection depends on left-ventricular shape.

Left-ventricular shape is an important determinant of regional wall mechanics during passive filling. To examine the influence of left-ventricular shape for the ejection phase, the distribution of active fiber stress at the beginning of ejection was calculated in a finite element study. Hereto, finite element models were constructed with varying left-ventricular shapes, ranging from an elongated ellipsoid to a sphere, but keeping the initial cavity and wall volume constant.

Geometric regularization for 2-D myocardial strain quantification in mice: an in-silico study.

Myocardial strain quantification in the mouse based on 2-D speckle tracking using real-time ultrasound datasets is feasible but remains challenging. The major difficulty lies in the fact that the frame rate-to-heart rate ratio is relatively low, causing significant decorrelation between subsequent frames. In this setting, regularization is therefore particularly important to discard motion estimates that are improbable.

The influence of left-ventricular shape on end-diastolic fiber stress and strain.

Passive filling is a major determinant for the pump performance of the left ventricle and is determined by the filling pressure and the ventricular compliance. We quantified the influence of left-ventricular shape on the overall compliance and the distribution of passive fiber stress and strain during the filling period in normal myocardium. Hereto, fiber stress and strain were calculated in a finite element analysis during the inflation of left ventricles of different shape, ranging from an elongated ellipsoid to a sphere, but keeping the initial cavity and wall volume constant.

A fast convolution-based methodology to simulate 2-D/3-D cardiac ultrasound images.

This paper describes a fast convolution-based methodology for simulating ultrasound images in a 2-D/3-D sector format as typically used in cardiac ultrasound. The conventional convolution model is based on the assumption of a space-invariant point spread function (PSF) and typically results in linear images. These characteristics are not representative for cardiac data sets.

On the calculation of principle curvatures of the left-ventricular surfaces.

A local description of the shape of the left ventricle is relevant in assessing the process of adverse ventricular remodeling, associated with most cardiac pathologies, and in monitoring reverse remodeling by therapy. To quantify local shape of the left ventricle, one can calculate the curvature of its epicardial or endocardial surface. The 3D geometry of the heart and especially the ventricles, can typically be described using finite element meshes.

Three-dimensional cardiac strain estimation using spatio-temporal elastic registration of ultrasound images: a feasibility study.

Current ultrasound methods for measuring myocardial strain are often limited to measurements in one or two dimensions. Cardiac motion and deformation however are truly 3-D. With the introduction of matrix transducer technology, 3-D ultrasound imaging of the heart has become feasible but suffers from low temporal and spatial resolution, making 3-D strain estimation challenging.