ISMRM 23rd Annual Meeting & Exhibition 30 May - 05 June 2015 Toronto, Ontario, Canada

Combined Educational & Scientific Session

UTE & Zero TE Imaging Techniques & Applications

SKILL LEVEL: Intermediate

ORGANIZERS: Eric Y. Chang, M.D., Garry E. Gold, M.D., Richard Kijowski, M.D., William B. Morrison, M.D., Ravinder R. Regatte, Ph.D. & Siegfried Trattnig, M.D.

Tuesday 2 June 2015

Overview
This hybrid course will provide an in-depth discussion of advanced functional imaging of musculoskeletal systems for evaluating joint mechanics, structure and composition. The lectures will discuss the technical aspects and the clinical and research applications of emerging MR methods, joint mechanics and function. The didactic lectures will be followed by presentation of scientific abstracts discussing novel MR methods for evaluating joint mechanics, structure and composition. This course is intended to bridge the gap between basic science research and clinical translation.

Target Audience
Radiologists and physicists who perform clinical imaging and/or research using advanced techniques.

Educational Objectives
Upon completion of this course, participants should be able to:
Recognize the added value of advanced UTE techniques for MSK diseases;
Describe the current UTE protocols and role of UTE in evaluation of cartilage, fibrocartilage, ligaments, bone , tendons; and
Integrate UTE techniques in routine clinical practice.

PROGRAM
Moderators: Jutta Ellermann, M.D., Ph.D., Felix W. Wehrli, Ph.D.
16:00   Quantitative UTE Techniques
Neal K. Bangerter, Ph.D.
16:30   Clinical Applications
Graeme M. Bydder, M.B., Ch.B.
17:00 0499.   
Performance of Bi-Component T2* Fitting of Bound and Pore Bone Water Fractions is Dependent on Field Strength
Alan C. Seifert1, Suzanne L. Wehrli2, and Felix W. Wehrli1
1University of Pennsylvania, Philadelphia, PA, United States, 2Children's Hospital of Philadelphia, Philadelphia, PA, United States

Discrimination between bound and pore bone water is vital for quantification of bone matrix density and porosity. The two main approaches are T2-selective magnetization preparation and bi-exponential T2* fitting. T2* of pore water, however, is shortened by field gradients arising from the difference in susceptibility between water and bone. We scanned human cortical bone specimens at 4 field strengths, and validated bi-exponential fitting against CT porosity and gravimetrically-determined matrix density. Our results indicate that T2* bi-exponential fitting of FIDs may be a suitable method for quantifying bound and pore water fractions at 1.5T, but may fail at higher field strengths.

17:12 0500.   Assessment of cortical porosity at 11.7 T and its correlation with CT porosity and biomechanics
Robert Nikolov1, Jun Chen1, Won Bae1, Reni Biswas1, Robert Healey1, Eric Chang1,2, Christine Chung1,2, Graeme Bydder1, and Jiang Du1
1Radiology, University of California, San Diego, San Diego, California, United States, 2Radiology, VA San Diego Healthcare System, La Jolla, California, United States

Conventional long echo time (TE) imaging sequences are not applicable to short T2 tissues such as cortical bone. However, through use of high resolution imaging afforded by 11.7T we are able to detect water found in the pores of cortical human bone and measure pore sizes and water fraction which correlate to: cortical porosity (CT), bound/unbound water ratio using UTE-MT (3T), and biomechanical properties. Average porosity (CT) correlates positively with percent water content (R2 = 0.47 ; p<0.001) and clusters of 5 voxels corresponding to a pore size of 8000 m2 (R2 = 0.62 ; p<0.001).

17:24 0501.   Actual Flip Angle Imaging to Improve T1 Measurement for Short T2 Tissues
Misung Han1, Peder EZ Larson1, Roland Krug1, and Viola Rieke1
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States

A variable flip angle method is a rapid T1 mapping method by exploiting steady-state signals at multiple flip angles. When combined with ultrashort echo-time imaging, T1 measurement for short T2* tissues is also possible. However, flip angle errors due to miscalibration or B1 inhomogeneities, and T2* relaxation effects during RF excitation can degrade the accuracy of T1 quantification. In this work, we propose the use of the actual flip imaging technique to correct flip angles to improve T1 measurement for short T2 tissues. Ex vivo study on bovine cortical bone and in vivo study on the Achilles tendon are presented.

17:36 0502.   
18F-FDG and 18F-NaF PET/MR Imaging of Osteoarthritis in the Knee: Considerations and Initial Results
Feliks Kogan1, Audrey Fan1, Sloane Brazina1, Dawn Holley1, Andrew Quon1, and Garry Gold1
1Department of Radiology, Stanford University, Stanford, CA, United States

New hybrid PET/MR systems allow for simultaneous, sensitive, and quantitative assessments of early bone activity in osteoarthritis (OA) with PET, which can be correlated with high-resolution quantitative MR methods of other tissues to study the pathogenesis of OA We demonstrate initial results of simultaneous time-of-flight PET/MR hybrid imaging of the knee OA. Results suggest that PET/MR may detect knee abnormalities unseen on MRI alone and is a promising tool for early detection of OA change in the bone.

17:48 0503.   Imaging of Grafted Mesenchymal Stem Cells in Bone Tissue
Sergey Magnitsky1, Geetha Mohan1, Curtis Corum2, Djaudat Idiyatullin2, Nancy Lane3, and Sharmila Majumdar1
1Radiology, UCSF, San Francisco, CA, United States, 2Radiology, University of Minnesota, MN, United States, 3UC Davis, CA, United States

Mesenchymal stem cells (MSCs) have high potential for a treatment of bone loss disease. Progress in this promising area of research will require an in vivo technique to observe the grafted cells and engraftment pattern overtime. We implemented SWIFT pulse sequence to develop an in vivo imaging protocol to monitor MSC engraftment in the bone tissue. Our preliminary experiments have shown that SWIFT pulse sequence allowed to generate a positive MR signal from iron labeled cells and detect grafted cells in cortical bones. Proposed method will have a profound impact on stem cell treatment of bone degenerative diseases.

18:00   Adjournment & Meet the Teachers