Alan C. Seifert¹, Cheng Li¹, Hamidreza Saligheh Rad¹, Chamith S. Rajapakse¹, Wenli Sun¹, Shing Chun Benny Lam¹, and Felix W. Wehrli^1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States

Increased cortical porosity is a major cause of impaired strength of osteoporotic bone. Ultrashort echo-time MRI can detect short-T2 components in cortical bone and enables measurement of bulk bone water content (BWC). The suppression ratio (SR, ratio of signal without and with long-T2 suppression) may better reflect bone porosity. BWC is quantified in 72 humans and SR in 40 humans and 13 bone specimens, and these measurements are compared to x-ray-based modalities. Although SR is not an absolute measurement of pore volume fraction, SR is more highly correlated with age and porosity than pQCT mineral density or BWC.

Thomas Baum¹, Stefan Ruschke¹, Olga Gordijenko¹, Eduardo Grande Garcia¹, Hendrik Kooijman², Rainer Burgkart³, Ernst J Rummeny¹, Jan S Bauer⁴, and Dimitrios C Karampinos^1
1Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Munich, Bavaria, Germany, ²Philips Healthcare, Hamburg, Hamburg, Germany, ³Department of Orthopedics and Orthopedic Sports Medicine, Technische Universität München, Munich, Bavaria, Germany,⁴Department of Neuroradiology, Klinikum rechts der Isar, Technische Universität München, Munich, Bavaria, Germany

There is a growing interest in understanding the linkage between bone marrow adiposity and bone weakening. The present pilot ex vivo study investigates, using human spine specimens, the relationship between MRS-based vertebral bone marrow proton density fat fraction, MDCT-based measures of BMD and trabecular microstructure, and biomechanical strength. The reported results confirm the previously reported negative association between bone marrow fat content and bone mineral density and provide the first direct validation of a negative association between bone marrow fat content and bone biomechanical strength.

Pippa Storey¹, Gregory Chang¹, Stephen Honig², Kashif Khokhar¹, Mary T. Bruno¹, David R. Stoffel¹, and Sandra L. Moore^1
1Radiology Department, New York University School of Medicine, New York, NY, United States, ²Division of Rheumatology, New York University School of Medicine, New York, NY, United States

Destruction of trabecular bone can result from osteoporosis or malignant processes, and is difficult to characterize adequately using conventional methodologies. We compared simultaneous fat, water and T2* mapping with high resolution trabecular imaging in the hips of 30 patients with osteoporosis or osteopenia. T2* is known to be sensitive to trabecular density since the magnetic susceptibility of mineralized bone differs from that of marrow. In addition, fat content may potentially allow discrimination of osteoporosis from malignant infiltration. Elevated T2* was found to be correlated with trabecular paucity, both in terms of anatomic distribution and across patients (Spearman r=0.64, p=0.00014).

Mary Kate Manhard^1,2, Sasidhar Uppuganti³, Mathilde C Granke³, Jeffry S Nyman³, and Mark D Does^1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Department of Orthopaedics & Rehab, Vanderbilt University, Nashville, TN, United States

Ultra-short echo time (UTE) measures of bound and pore water using the DAFP and AIR sequences were found in cortical bone of the radius in cadaveric specimens. The concentrations of bound and pore water were correlated to mechanical properties found from a three-point bend test. DXA and μCT imaging measures on the same bones were also correlated to mechanical properties. Bound and pore water correlated well with bending strength, while DXA and μCT showed slightly weaker correlations. Additionally, bound water was significantly correlated with toughness. These results validate the potential for MRI as a useful tool for predicting fracture risk.

Jiang Du¹, Shihong Li¹, Won Bae¹, Reni Biswas¹, Sheronda Statum¹, Eric Chang¹, and Christine B Chung^1
1Radiology, University of California, San Diego, San Diego, CA, United States

Magnetization transfer (MT) imaging is one way of indirectly assessing pools of protons with extremely fast transverse relaxation. However, conventional long TE MT imaging sequences are not applicable to short T2 tissues such as cortical bone. Ultrashort echo time (UTE) sequences can detect signal from short T2 species. The combination of UTE with MT (UTE-MT) provides a valuable option to assess different bone components. In this study we evaluated UTE-MT imaging of cortical bone and its application in assessing cortical porosity and biomechanical properties of cadaveric human bone samples using a clinical whole body 3T scanner.

Heather T. Ma¹, James F. Griffith², Chenfei Ye³, Xinxin Zhao⁴, and David K. Yeung^2
1Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, Guangdong, China, ²Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong, ³Department of Electronic and Information Engineering, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, Guangdong, China, ⁴Department of Electronic and Information Engineering, Harbin Institute of Technology Shenzhen Graduate School, Guangdong, China

This study characterized bone marrow perfusion properties in a quantitative way by adopting surrounding muscle as the reference. A muscle-based pharmacokinetic model was established by adapting a reference region-based model in the bone marrow. Contrast agent extravasation rate constants for bone marrow and the extravascular-extracellular volume fractions for muscle were observed to diminish with the decreased bone mineral density (BMD), while muscle perfusion indices had no significant change among groups with different BMD. The results indicated that the impaired perfusion function is only a function of the bone marrow and not of the adjacent musculature.