scholarly journals Rectus Femoris Knee Muscle Moment Arms Measured in Vivo During Dynamic Motion With Real-Time Magnetic Resonance Imaging

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Niccolo M. Fiorentino ◽  
Jonathan S. Lin ◽  
Kathryn B. Ridder ◽  
Michael A. Guttman ◽  
Elliot R. McVeigh ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Knee Joint ◽  
Healthy Subjects ◽  
Rectus Femoris ◽  
Resonance Imaging ◽  
Moment Arms ◽  
Joint Flexion ◽  
Tendon Excursion

Moment arms represent a muscle's ability to generate a moment about a joint for a given muscle force. The goal of this study was to develop a method to measure muscle moment arms in vivo over a large range of motion using real-time magnetic resonance (MR) imaging. Rectus femoris muscle-tendon lengths and knee joint angles of healthy subjects (N = 4) were measured during dynamic knee joint flexion and extension in a large-bore magnetic resonance imaging (MRI) scanner. Muscle-tendon moment arms were determined at the knee using the tendon-excursion method by differentiating measured muscle-tendon length with respect to joint angle. Rectus femoris moment arms were averaged across a group of healthy subjects and were found to vary similarly during knee joint flexion (mean: 3.0 (SD 0.5) cm, maximum: 3.5 cm) and extension (mean: 2.8 (SD 0.4) cm, maximum: 3.6 cm). These moment arms compare favorably with previously published dynamic tendon-excursion measurements in cadaveric specimens but were relatively smaller than moment arms from center-of-rotation studies. The method presented here provides a new approach to measure muscle-tendon moment arms in vivo and has the potential to be a powerful resource for characterizing musculoskeletal geometry during dynamic joint motion.

In Vivo Tracking of the Human Patella Using Cine Phase Contrast Magnetic Resonance Imaging

1999 ◽  
Vol 121 (6) ◽  
pp. 650-656 ◽  
Author(s):  
F. T. Sheehan ◽  
F. E. Zajac ◽  
J. E. Drace
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Knee Joint ◽  
Phase Contrast ◽  
Three Dimensional ◽  
Resonance Imaging ◽  
Contrast Magnetic Resonance ◽  
Knee Joint Kinematics ◽  
Cine Phase Contrast

Improper patellar tracking is often considered to be the cause of patellar-femoral pain. Unfortunately, our knowledge of patellar-femoral-tibial (knee) joint kinematics is severely limited due to a lack of three-dimensional, noninvasive, in vivo measurement techniques. This study presents the first large-scale, dynamic, three-dimensional, noninvasive, in vivo study of nonimpaired knee joint kinematics during volitional leg extensions. Cine-phase contrast magnetic resonance imaging was used to measure the velocity profiles of the patella, femur, and tibia in 18 unimpaired knees during leg extensions, resisted by a 34 N weight. Bone displacements were calculated through integration and then converted into three-dimensional orientation angles. We found that the patella displaced laterally, superiorly, and anteriorly as the knee extended. Further, patellar flexion lagged knee flexion, patellar tilt was variable, and patellar rotation was fairly constant throughout extension.

Finite Element Modeling of Knee Joint Contact Pressures and Comparison to Magnetic Resonance Imaging of the Loaded Knee

2003 ◽  
Author(s):  
Jiang Yao ◽  
Art D. Salo ◽  
Monica Barbu-McInnis ◽  
Amy L. Lerner
Keyword(s):  
Magnetic Resonance Imaging ◽  
Finite Element ◽  
Magnetic Resonance ◽  
Knee Joint ◽  
Material Properties ◽  
Three Dimensional ◽  
Resonance Imaging ◽  
Three Dimensional Model ◽  
Model Predictions

A finite element model of the knee joint could be helpful in providing insight on mechanisms of injury, effects of treatment, and the role of mechanical factors in degenerative conditions. However, preparation of such a model involves many geometric simplifications and input of material properties, some of which are poorly understood. Therefore, a method to compare model predictions to actual behaviors under controlled conditions could provide confidence in the model before exploration of other loading scenarios. Our laboratory has developed a method to apply axial loads to the in vivo human knee during magnetic resonance imaging, resembling weightbearing conditions. Image processing algorithms may then be used to assess the three-dimensional kinematics of the tibia and femur during loading. A three-dimensional model of the tibio-menisco-femoral contact has been generated and the image-based kinematic boundary conditions were applied to investigate the distribution of stresses and strains in the articular cartilage and menisci throughout the loading period. In this study, our goal is to investigate the contact patterns during long term loading of up to twenty minutes in the healthy knee. Specifically, we assess the use of both elastic and poroelastic material properties in the cartilage, and compare model predictions to known loading conditions and images of tissue deformations.

Monitoring stem cell migration in the nervous system by in vivo magnetic resonance imaging

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S692-S692
Author(s):  
Mathias Hoehn ◽  
Uwe Himmelreich ◽  
Ralph Weber ◽  
Pedro Ramos-Cabrer ◽  
Susanne Wegener ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Nervous System ◽  
Stem Cell ◽  
Cell Migration ◽  
Magnetic Resonance ◽  
Resonance Imaging ◽  
Stem Cell Migration

Supramolecular Enhancement of Aminoxyl ORCA Contrast Agents

2019 ◽  
Author(s):  
Hamilton Lee ◽  
Jenica Lumata ◽  
Michael A. Luzuriaga ◽  
Candace Benjamin ◽  
Olivia Brohlin ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Side Effects ◽  
Magnetic Resonance ◽  
Tobacco Mosaic Virus ◽  
Contrast Agents ◽  
Single Molecule ◽  
Organic Radical ◽  
Resonance Imaging ◽  
Physiological Conditions

<div><div><div><p>Many contrast agents for magnetic resonance imaging are based on gadolinium, however side effects limit their use in some patients. Organic radical contrast agents (ORCAs) are potential alternatives, but are reduced rapidly in physiological conditions and have low relaxivities as single molecule contrast agents. Herein, we use a supramolecular strategy where cucurbit[8]uril binds with nanomolar affinities to ORCAs and protects them against biological reductants to create a stable radical in vivo. We further over came the weak contrast by conjugating this complex on the surface of a self-assembled biomacromolecule derived from the tobacco mosaic virus.</p></div></div></div>

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