Lauren M Shapiro¹, Bragi Sveinsson^1,2, Marcus T Alley¹, Brian A Hargreaves¹, and Garry E Gold^1,3
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.

Burkhard Mädler¹, Jürgen Gieseke^2,3, and Volker A. Coenen^1
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.

Matthew F Koff¹, Lisa A Fortier², Scott A Rodeo³, Parina Shah¹, Bethsabe Romero⁴, Sarah Pownder², Rebecca Williams⁵, Suzanne Maher⁶, and Hollis G Potter^1
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.

Ashley Williams¹, Yongxian Qian², and Constance R Chu^1
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.

Fang Liu¹, Samuel A. Hurley¹, Nade Sritanyaratana², Walter F. Block^1,2, and Richard Kijowski^3
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.

Elli-Noora Salo^1,2, Timo Liimatainen³, Shalom Michaeli⁴, Silvia Mangia⁴, Jutta Ellermann⁴, Miika T. Nieminen^1,5, and Mikko J. Nissi^2,4
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

T₁ relaxation time has been proposed and demonstrated as a marker for articular cartilage degeneration. However, the sensitivity of T₁ to different tissue constituents remains somewhat unclear. In this study, we investigated T₁ relaxation dispersion at four clinically relevant spin-lock fields (B₁ = 125-1000 Hz) in proteoglycan- and collagen-specific enzymatic degradation models. The results suggest that the properties of the collagen network contribute significantly to T₁ relaxation and dispersion in cartilage. Increasing spin-lock power altered the T₁ sensitivity to the constituents, as well as the correlation with biomechanical properties.

Richard Kijowski¹, Donna Blankenbaker¹, Arthur De Smet¹, Geoffrey Baer², and Ben Graf^2
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.

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 Majumdar^1
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.

Jiang Du¹, Shawn Grogan², Won Bae¹, Christine B Chung¹, Darryl DLima², and Graeme M Bydder^1
1Radiology, University of California, San Diego, San Diego, California, United States, ²Scripps Clinic, San Diego, California, United States

 

Henry H. Ong¹, and Felix W. Wehrli^1
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.