|Muscle: Blood Flow & Physiology|
Dynamic BOLD MRI of Calf and Foot Muscles
Markus Klarhöfer1, Sebastian Kos2, Markus Aschwanden2, Augustinus Ludwig Jacob2, Klaus Scheffler1, Deniz Bilecen2
1University of Basel, Basel, Switzerland; 2University Hospital Basel, Basel, Switzerland
Purpose was to evaluate the feasibility of interleaved MR BOLD imaging in calf and foot muscles for the examination of blood supply of most peripheral tissues. 15 healthy volunteers underwent a short term ischemia / reactive hyperemia experiment. Simultaneous T2* mapping was possible with a temporal resolution of 1 second. Reactive hyperemia led to higher and faster T2* changes in m. soleus of the calf than in m. adductor hallucis of the foot. However, further studies have to clarify, if disorders in the vascular periphery cause significant changes of the T2* evolution in foot muscles during a cuff compression paradigm.
Hyperemic Flow Heterogeneity in Human Leg Muscle: An
MRI Study Using Arterial Spin Labeling
Wen-Chau Wu1, 2, Jiongjiong Wang1, John A. Detre1, Felix W. Wehrli1, Emile Mohler1, Sarah Ratcliffe1, Thomas F. Floyd1
1University of Pennsylvania, Philadelphia, USA; 2National Taiwan University, Taipei, Taiwan
We report the results of the application of continuous ASL (CASL) to systematically study perfusion differences between all major muscle groups in the calf. Results show that the hyperemic response to a 5-min ischemia is significantly larger in the deep flexor and soleus muscle than more superficial muscles. The finding correlates with the fiber composition of muscles. CASL proves to be able to detect the flow heterogeneity between muscle groups in human extremities. The ability to reliably measure heterogeneity may help understanding the vascular/metabolic mechanisms in skeletal muscle and possibly provide diagnostic information for the assessment of peripheral vascular disease.
Perfusion Tensor Imaging of Human
Kun Lu1, Eric C. Wong1, Lawrence R. Frank1, 2
1University of California San Diego, La Jolla, USA; 2VA, La Jolla, USA
The ability to non-invasively measure tissue perfusion is critical for assessing the physiological functions of human skeletal muscle in both healthy and disease states. The traditional techniques to measure tissue perfusion in human muscle are invasive and measure only bulk properties which do not render information on either spatial or temporal heterogeneity. Velocity selective arterial spin labeling (VSASL) MRI has been shown previously to be sensitive to muscle perfusion in humans , but does not allow a full exploration of important properties associated with the muscle perfusion, such as perfusion anisotropy and perfusion directions. Perfusion Tensor Imaging (PTI) was proposed in 2004 by Frank and Wong  in a study of perfusion anisotropy in the human brain, where VSASL was applied with a spherical velocity encoding scheme similar to that used in diffusion tensor imaging (DTI). The perfusion measurements can then be characterized by a perfusion tensor (P), analogous to the diffusion tensor in DTI, from which the estimates of the mean perfusion, fractional perfusion anisotropy and principle perfusion direction can be derived. This study demonstrates that PTI can also be used to measure perfusion properties of human skeletal muscle.
|16:36||607.||Mapping Functional Electrical Stimulation in
Denervated Thigh Muscles of Paraplegic Patients with T2 Parameter
Martin Meyerspeer1, 2, Thomas Mandl1, Martin Reichel1, Winfried Mayr1, Christian Hofer2, Helmut Kern3, Ewald Moser1
1Vienna Medical University, Vienna, Austria; 2Wilhelminenspital Vienna,, Vienna, Austria; 3Wilhelminenspital Vienna, Vienna, Austria
Functional electrical stimulation (FES) for paraplegic patients, with the long-term goal of restoring muscle function, has several positive therapeutic effects. In denervated muscle, FES induced activation follows the electrical field which can be modelled in simulations.For verifying these models, maps of relative T2 change induced by FES were calculated: T2 parameter images were acquired using multi-slice multi-spin-echo MRI before and after FES in 9 denervated paraplegic patients and 3 healthy subjects. Images acquired pre and post exercise were realigned and normalised.Results show that the training effect f FES of denervated muscles can be visualised by T2 parameter images.
Implementation of FAST-MRS in Mouse Permits the Rapid
Assessment of Muscle ATP Synthesis In-Vivo
Douglas E. Befroy1, Roberto Codella1, Gerald I. Shulman1, 2, Douglas L. Rothman1
1Yale University School of Medicine, New Haven, Connecticut, USA; 2Howard Hughes Medical Institute, New Haven, Connecticut, USA
The emergence of many transgenic mouse models with modulated muscle gene expression offers vast potential for the investigation of muscle metabolism. However, the application of the conventional saturation-transfer (CST) technique to assess metabolic reaction rates in mouse has been restricted by the small amount of muscle tissue available for MRS, necessitating very long experimental durations for a full CST experiment. We demonstrate that implementation of the Four-Angle Saturation Transfer (FAST) technique in mouse offers a rapid and practical alternative to CST for measuring muscle ATP synthesis in-vivo.
Detection of Residual Dipolar Couplings by 2D MRS
Techniques in Skeletal Muscle
S. Sendhil Velan1, Kartik Narasimhan1, Rolf F. Schulte2, Ali Bahu1, Richard G. Spencer3, Raymond R. Raylman1, Michael Albert Thomas4, Stephen E. Alway1
1West Virginia University, Morgantown, USA; 2GE Global Research, Munich, Germany; 3NIH/National Institute on Aging, Baltimore, USA; 4University of California, Los Angeles, Los Angeles, USA
In this study we employed localized 2D MRS approaches for detecting both J and residual dipolar couplings in skeletal muscle. The cross peaks in L COSY and J PRESS spectra can be generated by either J couplings usually observed in isotropic liquids, but normally not varying in size, or direct dipole-dipole interaction, only observable in oriented media. The residual dipolar couplings vanished in L COSY and collapsed in J PRESS spectra when the angle between the internuclear vector and the external magnetic field is 54 . Our results agree with the hypothesis that the elongated spaces between the actin and myosin chains hinder the creatine molecule from isotropic tumbling.
Metabolic Adaptations in Skeletal Muscle in
the Early Stage of Insulin Resistance Measured in Vivo by 1H and
Nicole M.A. van den Broek1, Henk MML De Feyter1, Klaas Nicolay1, Jeanine J. Prompers1
1Eindhoven University of Technology, Eindhoven, Netherlands
Literature suggests decreased mitochondrial oxidative capacity and intramyocellular lipid (IMCL) accumulation might be a major risk factor to develop insulin resistance. Skeletal muscle oxidative capacity and IMCL content in a rat model of early, lifestyle-induced insulin resistance was investigated using in vivo 1H and 31P MRS. After 2 weeks high-fat diet, Wistar rats were insulin resistant and had elevated IMCL levels compared to controls. Remarkably, tPCr is decreased in the insulin resistant rats. This means mitochondrial dysfunction does not play a role in the early stage of insulin resistance in a validated animal model of lifestyle-induced insulin resistance.
Mitochondrial Ultrasensitivity to ADP Explains Muscle
Energetics During Recovery from Exercise
Jeanine J. Prompers1, Nicole M.A. van den Broek1, Klaas Nicolay1, Jeroen A.L. Jeneson1
1Eindhoven University of Technology, Eindhoven, Netherlands
The recent discovery of extensive and dynamic protein phosphorylation in the mitochondrial matrix has rekindled the debate on the mechanistic underpinnings of energy balance in the active mammalian cell. We have previously reported evidence that the mitochondrial sensitivity to ADP may well be central to cellular energy balance. Here, we report new evidence in the form of rich 31P NMR spectroscopy data sets of ATP metabolism in human skeletal muscle and quantitative analysis of the post-exercise recovery state confirming our hypothesis that mitochondria are ultrasensitive to variations in the cytosolic concentration of the ATP hydrolysis product ADP.
|High Energy Phosphate Metabolism in Primary Biliary
Cirrhosis (PBC) Patients Monitored by 31P Magnetic Resonance
Spectroscopy: Abnormalities in PH Handling
Kieren Grant Hollingsworth1, Julia L. Newton1, Roy Taylor1, David E. Jones1, Andrew M. Blamire1
1Newcastle University, Newcastle Upon Tyne, UK
Primary Biliary Cirrhosis is an autoimmune liver disease with 50% of patients suffering profound, debilitating fatigue. This study uses phosphorus spectroscopy to non-invasively probe the concentrations of high-energy phosphates during a plantar flexion exercise. 8 healthy control subjects, 8 PBC patients without fatigue and 7 PBC patients with significant fatigue were put through two 3 minute periods of exercise, with loads of 25% and 35% of maximum voluntary contraction. Several significant abnormalities in pH and mitochondrial handling were found amongst the PBC patients, some of which affected all PBC patients and others which were restricted to the fatigued PBC patients.
Combined 31P MRSI and MRI Shows Distinct
Abnormalities in Affected Muscles in Facioscapulohumeral Muscular
Hermien E. Kan1, Dennis W.J. Klomp1, Marielle Wohlgemuth1, Tom W.J. Scheenen1, George W. Padberg1, Arend Heerschap1
1Radboud University Nijmegen Medical Center, Nijmegen, Netherlands
Facioscapulohumeral muscular dystrophy (FSHD) is characterized by asymmetric dysfunctioning of individual muscles. We used a combined approach of MRI and 31P MRSI to characterize anatomic and metabolic differences between affected and apparently non-affected muscles. We show, for the first time, dedicated application of 31P MRSI in affected and non-affected muscles in FSHD showing increased tissue pH and decreased PCr/ATP in affected muscles. Interestingly, non-affected muscles show no abnormalities, indicative of normal metabolism. It is unknown if this is also the case in other muscular dystrophies, as these are commonly studied by unlocalized 31P MRS