• Document: Musculoskeletal MRI Technical Considerations
  • Size: 8.92 MB
  • Uploaded: 2019-07-20 04:22:25
  • Status: Successfully converted


Some snippets from your converted document:

Musculoskeletal MRI
 Technical Considerations Garry E. Gold, M.D. Professor of Radiology, Bioengineering and Orthopaedic Surgery Stanford University Outline l Joint Structure l Image Contrast l Protocols: 3.0T Take-Home Points l RF Coil is key - for any MSK imaging l Consider 512 freq. matrix l Use IR, but selectively l Sequences and Imaging Planes Complementary Outline l Joint Structure l Image Contrast l Protocols: 3.0T Knee Tissues l Bone: cortical, cancellous l Marrow: fatty (yellow) hematopoietic (red) l Muscles l Tendons and ligaments l Cartilage: articular vs. fibrocartilage l Joint fluid Outline l Joint Structure l Image Contrast l Protocols: 3.0T Image Contrast l Concepts l Pulse Sequences l Fat Suppression Image Contrast l Concepts l Pulse Sequences l Fat Suppression Contrast - Concepts Sequences determine image contrast based on proton density and relaxation times Contrast Mechanisms Proton Density T2 Contrast T1 Contrast • Fat Suppression • Mixed or “T2/T1” contrast T2 Contrast Short Echo-Time (PD) Long Echo-Time (T2) Signal Joint Fluid Cartilage/Muscle Time • Long TR avoids T1 contrast Proton Density Fluid: higher signal relative to cartilage PD PD + Fat Sat T2 Fluid: very high signal relative to cartilage Dx? T1 Contrast Short TR Long TR Cartilage/Muscle Signal Signal Time Joint Fluid Time • Short TE avoids T2 contrast T1 Spin Echo Fluid: low signal relative to cartilage Image Contrast l Concepts l Pulse Sequences l Fat Suppression Image Contrast Pulse Sequences • Spin Echo • Fast/Turbo Spin Echo • Inversion Recovery (fast) • Gradient Echo • Special Purpose: 3D-FSE, T2-mapping Spin Echo • T1 weighting • Short TR, short TE • 1.5T: TR 600-800 ms • 3.0T: TR 800-1000 ms • Longer TR: More slices and better SNR Fast/Turbo Spin Echo l TE ~ 54-70 sufficient for T2W l Need less slice gap then SE l Blurring on PD weighted images l Longer TE, shorter ETL decreases blurring l Increasing receiver bandwidth decreases blurring l Never need conventional PD, T2 l T1 FSE possible with short ETL, high BW Image Space K-Space PD FSE/TSE - T2 Blurring PD FSE GRE FSE/TSE - Echo Train Length To avoid significant blurring artifact l PD Images: ETL 4-6 l T2W Images: ETL 8-12 * depends on receiver bandwidth Special Sequences l 3D FSE (SPACE, CUBE, VISTA) l Fast spin echo PD and T2 contrast l 3D imaging, little blurring l T2 Mapping l Cartilage collagen breakdown l Muscle after exercise 2D vs 3D Slab Imaging 2D Multislice 3D Slab l Shorter scan times • Averaging helps SNR l Efficient when TR is long • Continuous coverage and all slices can be interleaved • Better for image reformat 3D-FSE Knee at 3.0T 0.6 × 0.6 × 0.6 mm (256 × 256 × 200) in 8 minutes Coronal Sagittal Axial Acquisition Reformat Reformat 3D-FSE: Coronal Source 3.0T isotropic resolution of 0.6 mm 3D-FSE: Sagittal Reformat 3.0T isotropic resolution of 0.6 mm T2 Mapping Increased T2 relaxation time is a marker for decreased collagen organization in cartilage TE = 20 Signal TE = 40 Color T2 Map TE = 60 TE = 80 Echo Time (ms) Dardzinski BJ, et al. Radiology, 205: 546-550, 19

Recently converted files (publicly available):