Relaxometry in the Musculoskeletal System
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Monday 7 May 2012
Room 212-213  10:45 - 12:45 Moderators: Ari Borthakur, Christine Chung

10:45 0046.   
Rapid Volumetric T2 Measurements in Muscle Pre- and Post-Exercise using Quantitative DESS
Lauren M Shapiro1, Bragi Sveinsson1,2, Marcus T Alley1, Brian A Hargreaves1, and Garry E Gold1,3
1Department of Radiology, Stanford University, Stanford, CA, United States, 2Department of Electrical Engineering, Stanford University, Stanford, CA, United States, 3Department of Bioengineering, Stanford University, Stanford, CA, United States

Change in T2 relaxation time in muscle is an indication of muscle activity. Unfortunately, two-dimensional spin echo techniques to acquire T2 maps suffer from long acquisition times, blurring, artifacts and limited coverage. We evaluate the effect of exercise upon muscle T2 using a recently validated 3D quantitative DESS (qDESS) sequence in entire muscles at 3.0T. We compare T2 values in the medial and lateral gastrocnemius and tibialis anterior in 8 volunteers before exercise and at three points post-exercise. T2 values in all muscles peaked immediately post-exercise, and significant T2 differences between exercised and non-exercised legs were seen.

10:57 0047.   Introducing Dynamic Multi-exponential T2-Relaxation for Studying Muscle Pattern and Activation in the Human
Burkhard Mädler1, Jürgen Gieseke2,3, and Volker A. Coenen1
1Neurosurgery and Stereotaxis, University Bonn, Bonn, NRW, Germany, 2Philips Healthcare, Best, Netherlands, 3Radiology, University Bonn, Bonn, NRW, Germany

We successfully demonstrate the ability of acquiring high resolution in-vivo T2-relaxation data for quantitative multi-component analysis in human muscle with adequate B1-correction techniques. The T2-components identified are in agreement with recent non-spatially resolved studies from high SNR single voxel T2-experiment. The ability to monitor dynamic changes in muscle-compartmentalization might provide a powerful technique to assess the effectiveness of specific exercise and rehabilitation protocols and monitor treatment efficacy of interventions. This information may proof very valuable to understand compensatory muscle activation in the healthy human subjects as well as patterns associated with injury and/or pathophysiology.

11:09 0048.   Correlation of Meniscal T2* with Multiphoton Microscopy and Changes of Articular Cartilage T2 in an Ovine Model of Meniscal Repair
Matthew F Koff1, Lisa A Fortier2, Scott A Rodeo3, Parina Shah1, Bethsabe Romero4, Sarah Pownder2, Rebecca Williams5, Suzanne Maher6, and Hollis G Potter1
1Department of Radiology and Imaging - MRI, Hospital for Special Surgery, New York, New York, United States, 2College of Veterinary Medicine, Cornell University, Ithaca, New York, United States, 3Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, New York, United States,4Department of Molecular Medicine, Cornell University, Ithaca, New York, United States, 5Department of Biomedical Engineering, Cornell University, Ithaca, New York, United States, 6Department of Biomechanics, Hospital for Special Surgery, New York, New York, United States

MRI is commonly used to evaluate repairs of knee meniscus, and ultra-short echo imaging (UTE) allows for a quantitative assessment of the repair site. This study correlated T2* mapping using UTE imaging with quantitative histologic multiphoton microscopy (MPM) methods, and also evaluated the effect of meniscal repair on cartilage T2 values. Meniscal T2* values correlated with MPM measures of collagen content and crosslinking. Increased cartilage T2 values indicated an altered biomechanical loading pattern in the joint. These data lend strong support to the use of T2 and T2* applications to clinical meniscal repair and the assessment of risk for osteoarthritis.

11:21 0049.   Ultrashort TE-enhanced T2* mapping of deep articular cartilage detects sub-clinical degeneration
Ashley Williams1, Yongxian Qian2, and Constance R Chu1
1Cartilage Restoration Center, University of Pittsburgh, Pittsburgh, PA, United States, 2Magnetic Resonance Research Center, University of Pittsburgh

UTE-T2* mapping is sensitive to short-T2 signals and therefore has the potential to provide prognostic indication of otherwise clinically occult knee osteoarthritis in deep articular cartilage. UTE-T2* maps were evaluated in 53 human subjects. Significant elevations of UTE-T2* values in deep femoral condylar cartilage of subjects with ACL and/or meniscal injury without clinical evidence of subsurface cartilage abnormality suggest that UTE-T2* mapping is sensitive to sub-clinical cartilage degeneration. Significant decreases in UTE-T2* values measured longitudinally over 12 months following ACL reconstruction suggest that UTE-T2* can be used to quantitatively monitor changes to cartilage status in response to therapeutic interventions.

11:33 0050.   Multi-Exponential T2 Mapping of Human Patellar Cartilage Using mcDESPOT
Fang Liu1, Samuel A. Hurley1, Nade Sritanyaratana2, Walter F. Block1,2, and Richard Kijowski3
1Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 3Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, United States

mcDESPOT was used to create multi-exponential T2 relaxation time and water fraction maps of patellar cartilage in 3 asymptomatic volunteers at 3.0T in a 20 minute scan time. T2 and water fraction values for the tightly bound macromolecular water component (Wm) and loosely bound bulk water component (Wb) were similar to values reported for ex-vivo bovine cartilage specimens using NMR spectroscopy. T2 for the Wb component was higher in the superficial than the deep layer of cartilage. Wm fraction was higher in the deep layer of cartilage, while Wb fraction was higher in the superficial layer.

11:45 0051.   
T1rho dispersion in constituent-specific degradation models of articular cartilage with correlation to biomechanical properties
Elli-Noora Salo1,2, Timo Liimatainen3, Shalom Michaeli4, Silvia Mangia4, Jutta Ellermann4, Miika T. Nieminen1,5, and Mikko J. Nissi2,4
1Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland, 2Department of Applied Physics, University of Eastern Finland, Kuopio, Finland,3Department of Biotechnology and Molecular Medicine, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland, 4Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States, 5Department of Medical Technology, University of Oulu, Oulu, Finland

T1lower case Greek rho relaxation time has been proposed and demonstrated as a marker for articular cartilage degeneration. However, the sensitivity of T1lower case Greek rho to different tissue constituents remains somewhat unclear. In this study, we investigated T1lower case Greek rho relaxation dispersion at four clinically relevant spin-lock fields (lower case Greek gammaB1 = 125-1000 Hz) in proteoglycan- and collagen-specific enzymatic degradation models. The results suggest that the properties of the collagen network contribute significantly to T1lower case Greek rho relaxation and dispersion in cartilage. Increasing spin-lock power altered the T1lower case Greek rho sensitivity to the constituents, as well as the correlation with biomechanical properties.

11:57 0052.   T2 Mapping Sequence for Detecting Cartilage Lesion within the Knee Joint at 3.0T: Diagnostic Performance in 114 Patients with Surgical Correlation
Richard Kijowski1, Donna Blankenbaker1, Arthur De Smet1, Geoffrey Baer2, and Ben Graf2
1Radiology, University of Wisconsin, Madison, Wisconsin, United States, 2Orthopedic Surgery, University of Wisconsin, Madison, Wisconsin, United States

A routine MRI protocol consisting of multi-planar fast spin-echo sequences and a sagittal T2 mapping sequence were performed at 3.0T on the knee of 114 symptomatic patients who underwent subsequent arthroscopy. Two radiologists reviewed all MRI examinations to determine the presence or absence of cartilage lesions first using the routine MRI protocol alone and then using the routine MRI protocol along with the T2 maps. Adding the T2 mapping sequence to the routine MRI protocol improved the sensitivity for detecting surgically confirmed cartilage lesions from 72% to 88% with only a moderate reduction in specificity.

12:09 0053.   In plane T2 mapping and diffusion tensor imaging of lumbar nerve roots using a reduced-FOV acquisition
Dimitrios C Karampinos1, Gerd Melkus1, Timothy M Shepherd1, Suchandrima Banerjee2, Emine U Saritas3, Ajit Shankaranarayanan2, Chistopher P Hess1, Thomas M Link1, William P Dillon1, and Sharmila Majumdar1
1Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 3Department of Bioengineering, University of California, Berkeley, Berkeley, CA, United States

T2 mapping and diffusion tensor imaging may quantitate inflammatory changes to lumbar nerve roots affected by degenerative spine disease. However, imaging spinal nerve roots accurately is difficult due to their small caliber and oblique course in all three planes. We describe initial success using a reduced-FOV single-shot spin-echo EPI acquisition to obtain T2 mapping and DTI of the bilateral lumbar nerve roots at the L4 level for healthy volunteers.

12:21 0054.   Validation of bound and free water measurement using bi-component analysis of UTE images of cortical bone
Jiang Du1, Shawn Grogan2, Won Bae1, Christine B Chung1, Darryl DLima2, and Graeme M Bydder1
1Radiology, University of California, San Diego, San Diego, California, United States, 2Scripps Clinic, San Diego, California, United States


12:33 0055.   
Can bound and mobile bone water be distinguished by T2* at 9.4T?
Henry H. Ong1, and Felix W. Wehrli1
1Laboratory for Structural NMR Imaging, Departement of Radiology, University of Pennsylvania School of Medicine, Philadelphia, PA, United States

Differentiating bound and mobile bone water (BW) may provide valuable insight in bone health and microarchitecture. Previous reports have used T2* relaxometry to quantify bound and mobile BW at 0.6T and 3T. Here, we investigate the potential to quantify bound and mobile BW with T2* relaxometry at 9.4T. We compared 3-component exponential fits of FIDs from human cortical bone specimens with measurements of BW concentration, porosity, and bound and mobile BW fractions unambiguously quantified by deuterium NMR. The results show that at this field strength the 3-components primarily correlate with collagen protons and mobile BW but not with bound BW.