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Technical Advances in Musculoskeletal Imaging






Musculoskeletal MR imaging presents unique technological challenges. Although peripheral joints offer intrinsic rich soft tissue contrast the anatomy is often complex, with small structures, many of which course in oblique planes. High-resolution imaging of the small-scale anatomy of menisci, labra, carpal bones, and articular cartilage demand 2D multislice sequences with in-plane resolution of at least 0.5 mm (preferably 0.2 to 0.3 mm), with a slice thickness of 1 to 3 mm .The many soft tissue interfaces inherent to musculoskeletal anatomy and morphology also present challenges to successful imaging. Changes in magnetic susceptibility can occur at the interfaces between cartilage, cortical bone, and bone marrow. Therefore the Musculoskeletal Imaging whose Technical Advances, when placed in a magnetic field, these interfaces generate abrupt changes in local magnetic field gradients, creating a faster signal decay due to spin-spin dephasing (T2*). In addition, patients may have metallic prostheses or postsurgical metallic debris, which produce additional magnetic susceptibility artifacts.Fat, both in subcutaneous tissues and bone mar row, may also present imaging problems. The hyperintense signal of fat on conventional T1-weighted and proton density-weighted sequences can ob scure underlying pathology. In addition, at fat-water in terfaces, there may be a chemical shift artifact that degrades images. Finally, musculoskeletal soft tis sues have relatively short T2 relaxation times due to their highly organized molecular structure in fiber networks. The T2 relaxation of tendons and ligaments is in the range of a few milliseconds (msec) Technical Advances; that of cartilage is 10 to 30 msec. These structures also show a significant variation in T2 relaxation based on their physical orientation to the main magnetic field. When fibers form an angle of 55 degrees from the main magnetic field, T2 time be comes longer, generating a hyperintense signal.