Sarah Pownder¹, Matthew F Koff¹, Andrew James², Harry H Gebhard², Roger Hartl², Robby D Bowles³, Lawrence J Bonassar³, and Hollis G Potter^1
1Department of Radiolgy and Imaging - MRI, Hospital for Special Surgery, New York, NY, United States, ²Department of Neurological Surgery, Weill Cornell Brain and Spine Center, ³Department of Biomedical Engineering, Cornell University

This study used a clinical magnet (3T) to assess morphologic and quantitative MR features (T1rho and T2 mapping) of a rat tail with a tissue engineered disc replacement. The disc construct was shorter, wider and had a thicker annulus than the normal disc. The T2 values of the nucleus, annulus, and endplate of the disc construct were significantly shorter than the normal disc. T1rho values of the disc tended to be shorter than normal disc. This study demonstrates the feasibility of quantitative MRI, at clinically relevant field strengths, to assess preclinical intervertebral disc morphology and biochemical composition.

Chan Hong Moon¹, Lloydine Jacobs^2,3, Jung-Hwan Kim¹, Xiang He¹, James Kang^2,3, and Kyongtae Ty Bae^1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States, ²Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, United States, ³Ferguson Laboratory for Orthopaedic and Spine Research

We successfully obtained high-resolution, high-contrast T2 and T1rho images and measured T2 and T1rho in normal rabbit spine discs using in-house dual-tuned RF coil and SL sequence at 3T. Further study is necessary to demonstrate difference in T2 and T1rho between normal and degenerative disc models in rabbits in order to validate these imaging biomarkers for degenerative disc disease.

Rachelle Berger¹, Matthew Fenty², Bryan Fry¹, Philip M. Maurer³, Dawn M. Elliott⁴, and Ari Borthakur^2
1Department of Biochemistry & Molecular Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA, United States, ²CMROI, Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, PA, United States, ³3B Orthopaedics, Philadelphia, PA, United States, ⁴McKay Orthopaedic Lab, Department of Orthopaedic Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA, United States

The hypothesis was tested that T1ρ relaxation time combined with the disc height in patients with disc degenerative disease (DDD) can detect painful discs non-invasively. Mean values for both biomarkers individually exhibited significant differences between non-painful and painful discs. The combination of biomarkers improved the predictive value to 95% (area under the curve from a ROC analysis). The long-term objective of this study is to evaluate quantitative and non-invasive biomarkers of disc degeneration in patients with lower back pain.

CHENYANG WANG^1,2, MARK ELLIOTT³, THOMAS CONNICK³, WALTER WITSHCEY³, JOSEPH CALABRO⁴, ARI BORTHAKUR³, and RAVINDER REDDY^3
1SCHOOL OF MEDICINE, YALE UNIVERSITY, NEW HAVEN, CT, United States, ²BIOENGINEERING, UNIVERSITY OF PENNSYLVANIA, PHILADELPHIA, PA, United States,³RADIOLOGY, UNIVERSITY OF PENNSYLVANIA, PHILADELPHIA, PA, United States, ⁴SIEMENS MEDICAL SOLUTIONS, United States

Intervertebral disc degeneration is a common and sometimes painful condition. The initial sign of intervertebral disc degeneration involves the breakdown of proteoglycans and the accompanying depletion of Na+. Sodium MRI has previously been used to study the depletion of Na+ in intervertebral disc ex vivo. In this study, we carried out in vivo sodium MRI of intervertebral disc on a 7 T MRI scanner. The tissue [Na+] value calculated from the sodium MR images were correlated with intervertebral disc degenerative grade, in order to elucidate the trend in [Na+] content in IVDs undergoing degeneration.

L. Tugan Muftuler¹, Yen K Hong², Hon J Yu¹, Vance O Gardner³, Anton N Hasso⁴, and Nitin N Bhatia^5
1Center for Functional Onco-imaging, University of California, Irvine, CA, United States, ²Microbiology & Molecular Genetics, University of California, ³Orthopaedic Education and Research Institute, Orange, CA, ⁴Radiological Sciences, University of California, Irvine, CA, ⁵Orthopaedic Surgery, University of California, Irvine, CA

The majority of chronic back pain is associated with degeneration of the intervertebral disc (IVD), which can manifest itself in many different clinical conditions. The factors that lead to disc degeneration and its pathophysiology are still not completely understood. IVD is avascular; nutrition is supplied via diffusion mechanism from the capillary beds of the cartilaginous vertebral body endplates. Disruption in subchondral bone/endplate perfusion has long been suspected as a factor in pathogenesis of IVD degeneration. In the presented study we used dynamic contrast-enhanced MRI (DCEMRI) to investigate the endplate perfusion and its association with spinal disc degeneration.

Kathryn Jane Stevens¹, Pauline W Worters¹, Garry Evan Gold¹, Jarrett K Rosenberg¹, and Brian A Hargreaves^1
1Department of Radiology, Stanford University Medical Center, Stanford, CA, United States

MRI of the lumbar spine is often of limited value in patients after instrumented spinal fusion due to the extensive associated metal artifact. Slice Encoding for Metal Artifact Correction (SEMAC) is an MRI technique that corrects for spatial distortions by performing extra slice encoding and using view-angle tilting. MRI in 8 patients with previous spinal fusions demonstrated significantly decreased in-plane and through-plane artifact on SEMAC images compared to 2D FSE. This allowed improved visualization of the spinal canal, spinal nerve roots and neural foramina, which we hope will translate to improved diagnostic capabilities in patients with failed back surgery syndrome.

Michael J Wald¹, Chamith S. Rajapakse¹, Jeremy F. Magland¹, and Felix W. Wehrli^1
1Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States

Even though bone volume fraction is predictive of bone strength, the variation in mechanical properties with test direction requires inclusion of measures of structural orientation. Here, we examine whether the inclusion of trabecular bone fabric can improve the bone volume fraction-based prediction of the elastic constants derived from linear FE analysis of MR images of the distal tibia in specimens and live subjects. A strong power-law dependence of elastic moduli with bone volume fraction was observed, however the exponents depended on test direction and anatomical location. Inclusion of fabric information establishes a general model of the elastic constants independent of anatomical location and test direction.

Jenny Folkesson¹, Julio Carballido-Gamio², Dimitrios C Karampinos¹, Thomas Baum¹, Thomas M Link¹, Sharmila Majumdar¹, and Roland Krug^1
1Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States, ²Grupo Tecnologico Santa Fe, Mexico City, Mexico

The purpose of this work was to evaluate the feasibility of marrow composition quantification in high resolution proximal femur bone MRI. Automatic volume of interest placement was performed using an atlas built from IDEAL images . Separation of trabecular bone, red and yellow marrow was performed using 3-class fuzzy clustering. In the test cohort (2 fracture, 8 non-fracture females), fracture subjects had lower red marrow fraction (p<0.05). These initial results suggest that marrow composition analysis is feasible using HR MRI, and could potentially help understand underlying factors related to aging and fracture history.

Yusuf A Bhagat¹, Chamith S Rajapakse¹, Jeremy F Magland¹, Michael J Wald¹, Theresa M Scattergood², Peter J Snyder², and Felix W Wehrli^1
1Laboratory for Structural NMR Imaging, University of Pennsylvania, Philadelphia, PA, United States, ²Division of Endocrinology, Diabetes and Metabolism, University of Pennsylvania, Philadelphia, PA, United States

Recent advances in high-resolution structural imaging of trabecular and cortical bone and the use of these data as input into micro-finite-element (µFE) models have shown potential for assessing the effect of treatment in patients with osteoporosis. Here, we report initial baseline and select follow-up data in an ongoing investigation of women with low bone density (N=30) receiving either zoledronic acid or teriparatide, conducted at 3T and 7T. The baseline data show moderate associations with pQCT bone density while µFE-derived axial stiffness is strongly correlated with bone volume fraction at the same site. Finally, repeat data in select subjects indicate large anabolic effects.

Jerome L Ackerman^1,2, Yaotang Wu^2,3, Timothy G. Reese^1,2, Haihui Cao^2,3, Mirko I. Hrovat⁴, Steven P. Toddes⁵, and Rostislav A. Lemdiasov^5
1Martinos Center, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States,³Department of Orthopedic Surgery, Children's Hospital, Boston, MA, United States, ⁴Mirtech, Inc., Brockton, MA, ⁵InsightMRI, Inc., Leominster, MA, United States

Solid state MRI requires fast recovery of the scanner receiver in order to capture short T₂ signals with good fidelity. To circumvent the unacceptably long ³¹P receiver recovery time of a clinical scanner, we developed a frequency converter utilizing the fast recovery of the proton channel to acquire solid state ³¹P images of high quality. In effect, a special RF “front end” is interposed between the scanner and the ³¹P RF coil. Isotropic 3D ³¹P images of the bones of the wrists of volunteers were obtained with SNR ~30 in typically 37 min at 3T, exhibiting spatial resolution of ~5mm.