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Wen Ling¹, Ravinder R. Regatte², Gil Navon¹, Alexej Jerschow²

¹Tel Aviv University, Israel; ²New York University, New York, New York, USA

Glycosaminogycan (GAG) plays numerous vital functions in the human body. GAG concentration [GAG] in vivo is a sensitive biomarker indicative of both osteoarthritis (OA) and intervertebral disk (IVD) degenerative diseases. Currently existing techniques for GAG monitoring, such as, dGEMRIC (delayed gadolinium-enhanced MRI contrast), T1?, and 23Na MRI have some practical limitations. By exploiting the exchangeable protons of GAG we demonstrate that one can directly map the localized GAG concentration in vivo (gagCEST). The gagCEST approach is exploited on both human articular cartilage and animal IVD. Moreover, we also report the observation of the Nuclear Overhauser effect (NOE) from macromolecules in tissue, which contributes significantly to CEST/MT contrast mechanism in MRI and may lead to further diagnostic abilities.

Ernesto Staroswiecki¹, ², Neal Kepler Bangerter¹, Paul Thomas Gurney¹, Garry Evan Gold¹, Samantha Jane Holdsworth¹, Thomas Grafendorfer², Brian Andrew Hargreaves¹

¹Stanford University, Stanford, USA; ²GE Healthcare, Waukesha, USA

Quantification of sodium in cartilage correlates positively with proteoglycan content, making sodium MRI very attractive for tracking early degenerative changes associated with osteoarthritis. However, the challenges associated with in-vivo sodium imaging, including extremely rapid T2 relaxation decay, low concentration, and low gyromagnetic ratio, have hindered its adoption.  Short-TE gradient-spoiled sequences with efficient k-space trajectories can improve image quality. Accurate characterization of sodium T2* in the tissue of interest improves sequence parameter optimization and may be a marker of underlying physiologic structure.  In this work we present in-vivo measurements of sodium T2* in human articular cartilage at 3T and 7T.

Radu Ioan Bolbos¹, Benjamin C. Ma¹, Thomas M. Link¹, Sharmila Majumdar¹, Xiaojuan Li¹

¹University of California San Francisco, San Francisco, USA

Meniscus injury and cartilage degenerations preceded by damage of the collagen-proteoglycan (PG) matrix are present in acute knee injuries such as ACL tear. Previous studies have suggested potential associated degenerative processes of proteoglycans in meniscus and cartilage. T1 ρ relaxation time mapping techniques were used to assess lateral meniscus and adjacent cartilage in 16 patients with ACL tears. T1 ρ elevation in posterior horn of meniscus was significantly correlated with cartilage T1 ρ elevation in posterior compartment of LT, which demonstrated a strong injury-related relationship between meniscus and cartilage biochemical changes.

Jonathan Cheng¹, Ehsan Saadat¹, Radu Ioan Bolbos¹, Bjoern Jobke¹, Sarmad Muneeb Siddiqui¹, ², Michael D. Ries¹, Thomas M. Link¹, Xiaojuan Li¹, Sharmila Majumdar¹

¹University of California, San Francisco, San Francisco, California , USA; ²University of California, Berkeley, Berkeley, California , USA

We demonstrated that MR T1rho imaging is capable of quantifying proteoglycan (PG) content in human osteoarthritic articular cartilage. Human cartilage samples were harvested from total knee arthroplasty surgeries and imaged with T1rho ex vivo. Later, biopsy punches were taken from the samples and proteoglycan content was determined biochemically. T1rho relaxation times and PG content were significantly negatively correlated, showing a potential for T1rho to predict PG content in vivo.

Carl Siversson¹, Carl-Johan Tiderius¹, Leif Dahlberg¹, Jonas Svensson¹

¹Lund University, Malmo, Sweden

In 3D Look-Locker delayed Gadolinium enhanced MRI of cartilage (dGEMRIC) local flip angle variations may cause erroneous T1 values. The aim of this work was to evaluate the extent of this effect and try to correct for it in in vivo data. This was achieved by calculating and compensating for the local flip angle as it varies in the slice encoding direction, thus extending the number of slices usable for the dGEMRIC measurement.

Wei Li¹, Nitya Krishnan², Pottumarthi V. Prasad¹

¹Evanston Hospital and Northwestern University Feinberg School of Medicine, Evanston, Illinois, USA; ²Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA

The purpose of this study was to validate the accuracy of VFA approach for dGEMRIC in both phantoms and in vivo compared to standard 2D IR-TSE technique. Two separate phantom tests, one for estimating the optimal flip-angle combination and the other for evaluating the spread in T1 values across slices were performed. Four OA patients and 4 healthy human subjects were imaged sagittally using 2D IR-TSE and 3D VFA sequences. Our preliminary results indicate that VFA method is able to provide adequate accuracy of T1 for dGEMRIC, with major advantages of entire joint coverage and shorter acquisition times.

Ping-Chang Lin¹, Kenneth W. Fishbein¹, Richard G. Spencer¹

¹National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA

Mono-parametric characterization of cartilage with MRI has met with limited success; there is a large degree of overlap in mean parameter values for e.g. normal and OA cartilage.  We extend MRI analysis of cartilage by delineating the relationship between pairs of MR parameters pre- and post-enzymatic degradation.  Results are visualized as clusters of parameter values in two-dimensional space, with axes consisting of T₁, T₂, and MT rate taken pairwise.  We find that parameter clusters exhibit motion in parameter space defined by translation, rotation, and changes in shape and size, with differences seen between trypsin and collagenase digestion.

Jose G. Raya¹, Gerd Melkus², Olaf Dietrich¹, Daniel Ludwig Weber², Lucianna Filidoro¹, Maimilian Felix Reiser¹, Peter Michael Jakob², Christian Glaser¹

¹Ludwig Maximilian University of Munich, Munich, Germany; ²University of Würzburg, Würzburg, Germany

Articular cartilage is a highly structured tissue and plays an important role in the pathogenesis of osteoarthritis. The purpose of this work was to establish a protocol for multiparametric (T2, T1, ADC and FA) examination of healthy and diseased articular cartilage at 17.6T. Three differentiated zones (radial, transitional and tangential) could be identified in healthy cartilage, whereas no transitional zone was present in diseased cartilage. ADC and T2 were increased and FA reduced on diseased cartilage. Lesions appeared larger in the ADC and FA maps than in T2 maps indicating a higher sensitivity of DTI to loss of cartilage integrity.

Joshua Jay Jacobson¹, Rafael O'Halloran¹, Alexey A. Samsonov¹, Richard Kijowski¹, Sean B. Fain¹, Walter F. Block¹

¹University of Wisconsin Madison, Madison, Wisconsin, USA

T2 mapping can be used to quantify early changes consistent with cartilage degradation before changes can be detected in morphological scans.  However, the lengthy scan times approaching 10 minutes limit their utilization. We recognize that recent methods to exploit temporal correlations in time-resolved imaging (HYPR) can be applied to parametric imaging, by simply replacing the temporal dimension with a parametric dimension. We present a method to utilize an iterative constrained reconstruction algorithm with an undersampled acquisition to reduce scan time by a factor of four.

Jiang Du¹, Atsushi Takahashi², Christine B. Chung¹, Graeme M. Bydder¹

¹University of California, San Diego, San Diego, California , USA; ²GE Healthcare Technologies, Menlo Park, California , USA

The human musculoskeletal (MSK) system contains a variety of tissues with short T2 components such as the deep layers of articular cartilage, menisci, ligaments, tendons, entheses and cortical bone. The 2D UTE sequences allow these previously “MR invisible” tissues to be directly imaged and quantified. Here we present a UTE spectroscopic imaging (UTESI) technique for high resolution imaging and quantification, and apply it to six types of short T2 tissues in the MSK on a clinical 3T scanner