Imaging is performed with the patient in the supine position, arm at the side, and the shoulder slightly externally rotated . A dedicated surface coil is placed close around the shoulder to optimize signal-to-noise ratio. Imaging time usually is 1 hour or less.
Specific imaging protocols vary by institution. At our hospital the standard shoulder MRI protocol includes triplanar imaging. The following sequences are obtained: coronal oblique proton density (PD), coronal oblique T2 with fat saturation, sagittal oblique T2, sagittal oblique T1, and axial gradient echo.
Axial (transverse) images are obtained perpendicular to the long axis of the body. From an axial image through the supraspinatus muscle, the coronal oblique sequences are prescribed parallel to the supraspinatus tendon. Sagittal oblique sequences then are oriented perpendicular to the coronal images.
For MR arthrography gadolinium contrast is injected directly into the gleno-humeral joint under fluoroscopic guidance. The injected solution distends the capsule, separates the glenohumeral ligaments, and outlines intra-articular structures.
Corresponding author. E-mail address: [email protected] (W.E. Palmer).
At the authors' hospital a 22- or 20-gauge 3.5 in spinal needle is inserted into the glenohumeral joint and approximately 12 mL of a solution containing gadolinium, normal saline solution, iodinated contrast, and lidocaine is injected. (Solution is made by mixing 0.4 mL of gadopentate dimeglumine with 50 mL of normal saline. Then 10 mL of this solution is mixed with 5 mL of iodinated contrast and 5 mL of preservative-free lidocaine 1%.) MRI is initiated within 30 min before fluid in the joint can be resorbed .
Triplanar T1 sequences with or without fat suppression are obtained to take advantage of the contrast provided by the injected solution. A T2-weighted sequence is performed to evaluate the extra-articular structures for pathology, such as bursal surface partial-thickness rotator cuff tear, soft tissue mass, and bone marrow abnormality.
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