SPECIAL INTEREST SESSION
Biomechanics
Wednesday 22 April 2009
Room 312 16:00-18:00

Moderators:

 Kimberly K. Amrami and Bruce M. Damon
 
16:00 547. Quantitative Analysis of the Post-Contractile BOLD Effect in Human Skeletal Muscle
    Theodore F. Towse1, Jill M. Slade2,3, Jeffrey A. Ambrose1, Mark C. DeLano2, Ronald A. Meyer1,2
1Physiology, Michigan State University, East Lansing, MI, USA; 2Radiology, Michigan State University, East Lansing, MI, USA; 3Manipulative Medicine, Michigan State University, East Lansing, MI, USA
    Brief single contractions of muscle are followed by increases in blood flow and oxygenation, resulting in a post-contractile BOLD response. This study shows that the magnitude and time course of muscle post-contractile BOLD responses are quantitatively explained from changes in muscle blood volume and hemoglobin saturation measured by near-infrared spectroscopy (NIRS). Furthermore, using a simple one-compartment vascular model the NIRS and MRI changes can be accurately predicted from changes in muscle blood flow and oxygen consumption.
     
16:12 548. Twisting Motion as a Confound to Skeletal Muscle BOLD
    Andrew D. Davis1,2, Greg D. Wells3,4, Bereket Falk5, Michael D. Noseworthy6,7
1Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada; 2Medical Physics and Applied Radiation Sciences, St. Joseph's Healthcare, Hamilton, Ontario, Canada; 3Department of Anesthesia, University of Toronto, Toronto, Ontario, Canada; 4Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; 5Department of Physical Education and Kinesiology, Brock University, St. Catharines, Ontario, Canada; 6Electrical and Computer Engineering, School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada; 7Brain-Body Institute, St. Joseph's Healthcare, Hamilton, Ontario, Canada
    BOLD data was acquired at 3T in skeletal muscle of the lower leg during an on/off isometric exercise paradigm. This was compared to data taken by substituting a twisting motion for the exercise. Both data sets were analysed using a square wave based GLM. The twisting data was found to mimic the exercise data, confounding the analysis. In-plane twists must therefore be eliminated from during-exercise BOLD scans, since the motion effects may be mistaken for true changes in perfusion and oxygenation.
     
16:24 549. Development of a Spin Tag Sequence with Spiral Acquisition for Elucidating Shear at the Deep Gastrocnemius Aponeurosis and Other Dynamics of the Musculoskeletal Elements of the Lower Leg
    Gajanan Nagarsekar1, John Hodgson1, David Shin1, Shantanu Sinha1
1Radiology, University of California at San Diego, San Diego, CA, USA
    In order to visualize dynamics of the active and passive components of the musculoskeletal system at 100% maximum voluntary contractions, a rapid method using gated spin tagging with spiral acquisition was developed that allowed acquisition of high resolution images in 16~21 contractions. Movement of soleus and gastrocnemius during isometric and passive plantar-flexion was imaged in 6 subjects using a home-built computer controlled foot pedal device. Significant differences in displacement between the two muscles were observed. These surprising findings suggest minimal mechanical interactions between the soleus and gastrocnemius aponeuroses and significant functional disparity between adjacent regions of soleus and gastrocnemius muscles.
     
16:36 550. Dependence of the Ratio of Fiber Length Strain to Aponeurosis Strain (Gear Ratio) of the Human Medical Gastrocnemius on Anatomical Position and Loading Conditions
    David Dongsuk Shin1, John A. Hodgson2, Gajanan Nagarsekar3, V Reggie Edgerton2, Shantanu Sinha3
1Biomedical Engieering, University of California, Los Angeles, CA, USA; 2Physiological Science, University of California, Los Angeles, CA, USA; 3Radiology, University of California, San Diego, CA, USA
    Velocity encoded phase contrast MRI and a computer-controlled hydraulic ankle rotation apparatus were used to measure the in vivo gear ratio of the medial gastrocnemius (MG) in 6 healthy human subjects. The gear ratio changed significantly in three regions of MG, increasing from distal to proximal (distal: 1.00 ± 0.03, mid: 1.10 ± 0.02, proximal: 1.22 ± 0.03). Slightly less gain was observed in passive (1.13 ± 0.02) compared to active mode (1.08 ± 0.03). For the first time, the architectural parameter of gear ratio and its variation with anatomical position under different loading and movement conditions were measured.
     
16:48 551. Hamstrings and Quadriceps Muscle Displacements During Knee Joint Flexion as Determined by 3D DENSE
    Niccolo Fiorentino1, Xiaodong Zhong2, Michael Rehorn2, Fred Epstein2,3, Silvia Blemker1,2
1Mechanical & Aerospace Engineering, University of Virginia, Charlottesville, VA, USA; 2Biomedical Engineering, University of Virginia, Charlottesville, VA, USA; 3Radiology, University of Virginia, Charlottesville, VA, USA
    A 3D DENSE sequence was used to image a volume of tissue in the mid-to-distal thigh during knee joint flexion. Three-dimensional displacements for the quadriceps and hamstrings muscle groups were determined in 20 transverse 5-mm slices and over 80% of the flexion motion. The mean reconstructed displacements of the hamstrings and quadriceps muscle groups were found to be 2.9 +/- 1.2 mm and -1.4 +/- 0.7 mm, respectively, which is expected from a protagonist-antagonist pair. This study demonstrates that 3D cine DENSE MRI is a feasible method for capturing the 3D deformation of skeletal muscle tissue volumes.
     
17:00 552. Vibration Imaging for Functional Analysis of Flexor Muscle Compartments
    Yogesh Kannan Mariappan1, Kevin J. Glaser1, Armando Manduca2, Richard L. Ehman1
1Department of Radiology, Mayo clinic, Rochester, MN, USA; 2Biomathematics resource, Mayo clinic, Rochester, MN, USA
    We investigated a novel technique for the analysis of the functional compartments of the forearm flexor muscles. The fingers were vibrated individually with pressure-activated drivers and the resultant motions within these muscles were imaged with a modified phase-contrast MR imaging technique that is highly sensitive to cyclic motion. The results show that this technique provides detailed mapping of the regions of the complex flexor muscle compartment that correspond to each digit for both the flexor digitorum profundus and the flexor digitorum superficialis. The results also demonstrate the extent of mechanical interdependence between flexors, offering potential methods for studying normal and abnormal hand and wrist biomechanics.
     
17:12 553.

Dynamic 31P MRS of Exercising Human Muscle in a 7T Whole Body System, with STEAM and Semi-LASER Localisation
    Martin Meyerspeer1,2, Thomas Mandl1,2, Tom Scheenen3, Ewald Moser1,2
1Center for Biomedical Technology and Physics, Vienna Medical University, Vienna, Austria; 2High Field MR Centre of Excellence, Vienna Medical University, Vienna, Austria; 3Radiology (667), Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands
    We demonstrate that localised 31P MRS can be used to follow metabolic changes with high temporal resolution and, by selecting a single muscle, high specificity in a 7T whole body scanner. The SNR benefit of the high field strength can be exploited, as localised high order shimming yielded line widths comparable to previous results at 3T, even during and after tissue motion under exercise. In consequence, PCr recovery curves were successfully fitted to non-averaged single acquisitions (TR=8s) of spectra localised in a single exercising muscle, yielding consistent results. Application of adiabatic 31P-semi-LASER further increased SNR in comparison with 31P-STEAM.
     
17:24 554.

Dual Gradient Echo MRI Method for the Evaluation of Muscle Microvascular Function
    Otto Alexander Sanchez1, Elizabeth Anne Copenhaver1, Marti Ann Chance1, Michael James Fowler2, Jane Kent-Braun3, Bruce Murray Damon1,4
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA; 2Diabetes, Endocrinology, & Metabolic Division, Vanderbilt University, Nashville, TN, USA; 3Kinesiology, University of Massachusetts-Amherst, Amherst, MA, USA; 4Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
    To test the ability of a dual GRE MRI method to detect microvascular dysfunction, the time course of SI6 and SI46 , reflecting blood volume and %HbO2, respectively were compared between healthy subjects and individuals at high risk of microvascular disease (type 2 diabetics). Changes in SI between baseline and peak (δSI) and time to peak TTP following isometric contractions of 50%MVC and MVC were compared between groups. Subjects with type 2 diabetes had a higher BMI and HbA1c values than healthy individuals. δSI6 and δSI46 were significantly lower in diabetic subjects following 50%MVC. This method can potentially detect microvascular dysfunction.
     
17:36 555. 23Na-MRI Contrasts for Application in Muscular Sodium Channel Diseases
    Armin Michael Nagel1, Marc-André Weber2, Christian Matthies1, Julien Dinkel, Karin Jurkatt-Rott3, Frank Lehmann-Horn3, Lothar Rudi Schad4
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; 2Department of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany; 3Applied Physiology, University Ulm, Ulm, Germany; 4Computer Assisted Clinical Medicine, Faculty of Medicine Mannheim, University Heidelberg, Mannheim, Germany
    Three different 23Na-MRI contrasts were applied and compared with regard to the information they provide about the compartments from which the 23Na signal originates. In particular, a T1-weighted, a concentration-weighted contrast, and an inversion recovery sequence, the latter of which suppresses the 23Na fluid signal were used. It was shown that the 23Na-IR sequence is well suitable to visualize an intracellular sodium accumulation, caused by provocation of the lower leg muscles in patients with hypokalemic periodic paralysis, a muscular sodium channelopathy. This is substantiated by the fact, that the total sodium concentration stays constant after provocation.
     
17:48 556. Effects of a 3-Month Training Program on Muscular Lipid Metabolism and Physical Health in Sedentary Non-Insulin-Dependant Diabetes Mellitus Patients
    Michael Ith1, Monika Mattes-Schaub1, Roland Kreis1, Kim-Anne Lê2, Luc Tappy2, Jean-Paul Schmid3, Emanuel Christ4, Chris Boesch1
1Department Clinical Research, University Bern, Bern, Switzerland; 2Physiology Department, University Lausanne, Lausanne, Switzerland; 3Cardiology Department, University Bern, Bern, Switzerland; 4Diabetology Department, University Bern, Bern, Switzerland
    For patients with impaired insulin sensitivity there is a clear consensus that weight loss improves their metabolic state, however, the effect of increased physical activity is less clear. This study therefore aimed to investigate the effects of a 3-month structured training program on physical performance, clinical parameters as well as levels and utilization of intramyocellular lipids (IMCL) in patients with non-insulin dependent diabetes mellitus type 2. The presented results will demonstrate a significant improvement of metabolic state and physical performance together with reduced levels of IMCL thereby approaching values of a simultaneously investigated control group.