MRI Analysis of Bone & Physeal Cartilage
Friday 24 April 2009
Room 312 10:30-12:30

Moderators:

 Jiang Du and Felix W. Wehrli
 
10:30 842. Bulk Susceptibility Mapping Using Ultrashort TE Spectroscopic Imaging (UTESI)
    Jiang Du1, Alan Chiang1, Atsushi M. Takahashi2, Christine B. Chung1, Graeme M. Bydder1
1Radiology, University of California-San Diego, San Diego, CA, USA; 2Global Applied Science Laboratory, GE Healthcare Technologies, Menlo Park, CA, USA
    Bulk magnetic susceptibility (BMS) effects have received attention in high resolution solid state NMR and in MR imaging of heterogeneous or compartmentalized structures, such as the Achilles tendon and bone. It is difficult to directly quantify BMS effects in these short T2 tissues using clinical MR scanners with conventional sequences. Ultrashort TE spectroscopic imaging (UTESI) provides high resolution imaging of short T2 tissues, and allows BMS effects to be evaluated in vivo. In this study we applied the UTESI technique to investigate BMS in the Achilles tendon and cortical bone of healthy volunteers using a clinical 3T scanner.
     
10:42 843. Creating Short T2 Contrast with Three-Dimensional Ultrashort TE (3D UTE) Imaging
    Jiang Du1, Atsushi M. Takahashi2, Sheronda Statum1, Reni Biswas1, Christine B. Chung1, Graeme M. Bydder1
1Radiology, University of California-San Diego, San Diego, CA, USA; 2Global Applied Science Laboratory, GE Healthcare Technologies, Menlo Park, CA, USA
    There is increased interest in imaging short T2 species such as the meniscii, tendons and cortical bone. These tissues show little or no signal with conventional MR sequences. Short T2 contrast is typically generated either with echo subtraction or long 90„a saturation pulses followed by gradient dephasing. Here we report on a 3D UTE sequence (minimum TE = 8 ƒÝs) using several long T2 suppression techniques including long T2 saturation, adiabatic inversion, dual echo subtraction, and combinations of these. The efficacy of these approaches was demonstrated through in vitro and in vivo imaging of meniscii, tendons and cortical bone.
     
10:54 844. Detection of Short-Term Temporal Changes in Mechanical Properties of Bone in Early Postmenopausal Women Using μMRI
    Chamith S. Rajapakse1, Jeremy Magland1, Peter J. Snyder2, Felix W. Wehrli1
1Laboratory for Structural NMR Imaging, University of Pennsylvania School of Medicine, Philadelphia, PA, USA; 2Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
    Next to bone volume fraction, the architecture of the trabecular network determines the bone’s mechanical competence. Here we examined the changes in Young’s and shear moduli of the trabecular bone in the distal tibia immediately following menopause in women receiving either estradiol or no treatment. Mechanical parameters were estimated on the basis of micro-finite-element analysis using grayscale MR images as input into the model. Results suggest that estradiol preserves the elastic moduli whereas absence of estrogen supplementation leads to a reduction in mechanical parameters ranging from 3-5% (p<0.005) over a 24-month period.
     
11:06 845. MR Multi-Parametric Approach to Evaluate Osteoporosis at 3T: T2, T2*, ADC, Gi and 1H-MRS Measurements in Healthy, Osteopenic and Osteoporotic Subjects
    Silvia Capuani1, Mauro Rebuzzi1, Fabrizio Fasano2,3, Gisela Hagberg2, Marco Di Mario4, Bruno Maraviglia5, Vincenzo Vinicola6
1CNR-INFM SOFT, Physics Department Sapienza University of Rome, Rome, Italy; 2Santa Lucia Foundation, Neuroimaging Laboratory, Rome, Italy; 3Siemens Medical, Milan, Italy; 4Santa Lucia Foundation, Radiology Department, Rome, Italy; 5MARBilab Enrico Fermi Center, Rome, Italy; 6Santa Lucia Foundation, Rehabilitation Hospital, Rome, Italy
    Aims of this study were: 1) to correlate T2, T2*, ADC and Gi of the calcanei spongy-bone measured in healthy, osteopenic and osteoporotic women with their correspondent bone-marrow fat-content, assessed by 1H-MRS and their T-score 2) to assess the ability of each MR parameter to predict the osteopenic and/or osteoporotic status of bone; 3) to identify the MR-parameter which better predicts the bone fracture risk. Our results show the great potentiality of ADC and T2* in combination with 1H-spectroscopy in the diagnosis of osteoporosis. This study highlights that the best parameter to assess the bone status is skeletal-site-dependent.
     
11:18 846. Combined Water and Fat Suppressed Proton Projection MRI (WASPI) and Micro CT Measurement of Bone Mineralization
    Haihui Cao1,2, Jerome Ackerman2,3, Thomas D. Crenshaw4, Patricia Dunning5, Melvin Glimcher1,2, Yaotang Wu1,2
1Department of Orthopaedic Surgery, Children's Hospital, Boston, MA, USA; 2Harvard Medical School, Boston, MA, USA; 3Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; 4Department of Animal Sciences, University of Wisconsin, Madison, WI, USA; 5Department of Radiology, Children's Hospital, Boston, MA, USA
    Non-invasive measurement of the degree of bone mineralization is critical for the diagnosis of metabolic bone diseases. Combined WASPI and Micro CT was utilized to measure degree of mineralization of porcine bone specimens from pigs fed diets with either marginal or excess Calcium and Phosphorus. By transferring CT and MRI images into one coordinate system, one can extract bone mineral density measured by micro CT and bone matrix density measured by WASPI from the same region of interest. The preliminary data show potential merits of combined WASPI and micro CT measurements for noninvasive in vivo characterization of bone mineralization.
     
11:30 847. Magnetic Resonance Elastography in Trabecular Bone: Preliminary Results
    Jun Chen1, Hugh McGregor1, Kevin Glaser1, Yogesh Mariappan1, Arunark Kolipaka1, Richard Ehman1
1Mayo Clinic, Rochester, MN, USA
    Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue leading to diminished biomechanical competence of the skeleton and low-trauma or atraumatic fractures. Assessing the overall biomechanical properties of the bone, is more valuable than BMD alone for osteoporosis diagnosis. This work demonstrated the feasibility of using MRE to measure the stiffness of trabecular bone (TB). High-frequency mechanical flexural waves were induced in the bone. Spin-echo MRE successfully recorded the submicron mechanical motions in the bone, using the marrow soft tissue as a marker. The beam inversion yielded trabecular bone stiffness values that agree with results in the literature. We speculate that with optimized drivers and sequences these MRE methods can be applied in vivo, to directly measure the stiffness of trabecular bone in extremities.
     
11:42 848. The Ultrastructure of Bone Using Selective Saturation in SWIFT at 9.4 T
    Jutta Ellermann1,2, Djaudat Idiyatullin2, Curt Corum2, Steen Moeller2, Wen Ling2, Michael Garwood2
1Department of Radiology, University of Minnesota Medical Center, Minneapolis, MN, USA; 2Center for Magnetic Resonance Research, University of Minnesota Medical Center, Minneapolis, MN, USA
    In musculoskeletal imaging there is an abundance of water and fat interfaces leading to problems of image blurring. These interfaces are particularly programmatic when acquiring images with very short TE in order to visualize rapidly decaying signals such as cortical bone, tendons etc. Such an imaging acquisition approach is recently introduced, novel acquisition scheme SWIFT (Sweep Imaging with Fourier Transform) which operates with an effective TE~0. Here we introduce for the first time a water/fat saturation scheme in SWIFT and demonstrate that selectively saturated SWIFT images display resolved bone ultrastructure including lamellar organization of bone, tendon- cortical bone interface and trabeculae.
     
11:54 849. Registration of MR Trabecular Bone Images of the Proximal Femur in a Longitudinal Study
    Janet Blumenfeld1, Julio Carballido-Gamio2, Jenny Folkesson2, Dana Carpenter2, Thomas M. Link2, Sharmila Majumdar1,2
1Bioengineering, UC-Berkeley/UC-San Francisco, San Francisco, CA, USA; 2Radiology, UC-San Francisco, San Francisco, CA, USA
    This study is the first time that image registration has been implemented in a longitudinal study investigating changes in MR-derived trabecular bone structure. Image registration ensures that the same analysis region is used in baseline and follow-up images. The registration technique uses a mutual information based method to accurately register longitudinal MR images of the proximal femur. Results demonstrate improved accuracy in trabecular bone measurements between baseline and one year follow-up images and suggest that this algorithm is robust enough to be used routinely in longitudinal studies of trabecular bone in other musculoskeletal sites, such as the tibia and wrist.
     
12:06 850. Correlation of MRI and Histological Examination of Physeal Bars in a Rabbit Model
    Matthew F. Koff1, LeRoy Chong2, Patrick Virtue3, Liang Li Ying4, Li Foong Foo1, Hollis Potter1
1Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, USA; 2Department of Diagnostic Radiology, Changi General Hospital, Singapore; 3GE Healthcare, Waukesha, WI, USA; 4Department of Orthopedic Surgery, Hospital for Special Surgery, New York, NY, USA
    A bony bridge, or bar, across an open growth plate may be evaluated with MRI. This study used an animal model to validate indirect measurements of bar area from MR images with direct histological measurements. A bar was created in the tibia of 18 rabbits. At 6 weeks post-op, volumetric ex-vivo MR images of the knee were acquired. The bar area was calculated from a 3D reconstruction of the segmented images and from matching histologic sections of the tibia. A strong correlation (r=0.8) was found between the measurements. The results provide a foundation for quantitative evaluation of in-vivo human physes.
     
12:18 851. Examination of the Correlation Between Hypervascularity and Physeal Bone Bridge Formation
    Bernhard Neumayer1, Eva Elisa Fischerauer2, Clemens Diwoky1, Annelie-Martina Weinberg2, Rudolf Stollberger1
1Institute of Medical Engineering, TU Graz, Graz, Austria; 2Department for Paediatric and Adolescent Surgery, Medical University of Graz, Graz, Austria
    The formation of bone bridges can be initiated by physeal lesions or by implants advanced through the growth plate. An incomplete decomposition of these structures can lead to full or partial growth arrest. This study documented the formation of bone bridges and examined hypervascularity as one hypothesized underlying mechanism. Five Sprague-Dawley rats were subjected to growth plate lesion and morphology and vascularity were observed using MRI. Polymerase chain reaction analyses for a different cohort being subjected to the same treatment investigated growth and oxygenation factors. Correlation of results of RRM and PCR analyses confirm hypervascularity prior to bone bridge formation.