Gradient-recalled echo sequences in direct shoulder MR arthrography for evaluating the labrum.

OBJECTIVE: The purpose of this study was to determine the utility of fat-suppressed gradient-recalled echo (GRE) compared with conventional spin echo T1-weighted (T1W) sequences in direct shoulder MR arthrography for evaluating labral tears. MATERIALS AND METHODS: Three musculoskeletal radiologists retrospectively reviewed MR arthrograms performed over a 12-month period for which surgical correlation was available. Of 180 serial arthrograms, 31 patients had surgery with a mean of 48 days following imaging. Paired coronal oblique and axial T1W or GRE sequences were analyzed by consensus for labral tear (coronal oblique two-dimensional multi-echo data image combination, 2D MEDIC; and axial three-dimensional double-echo steady-state, 3D DESS; Siemens MAGNETOM Sonata 1.5-T MR system). Interpretations were correlated with operative reports. RESULTS: Of 31 shoulders, 25 had labral tears at surgery. The GRE sequences depicted labral tears in 22, while T1W images depicted tears in 16 (sensitivity 88% versus 64%; p<0.05). Subdividing the labrum, GRE was significantly more sensitive for the posterior labrum (75% versus 25%; p<0.05) with a trend toward greater sensitivity at the anterior labrum (78% versus 56%; p=0.157) but not significantly different for the superior labrum (50% versus 57%; p>0.7). Specificities were somewhat lower for GRE. CONCLUSION: Thin section GRE sequences are more sensitive than T1W for the detection of anterior and posterior labral tears. As the specificity of GRE was lower, it should be considered as an adjunctive imaging sequence that may improve depiction of labral tears, particularly smaller tears, in routine MR arthrography protocols.

Ultrasound of the knee.

Ultrasound of the knee is best suited for the evaluation of tendons, fluid collections and effusion, synovitis, periarticular soft tissue masses, muscles, and the collateral ligaments. Advantages of sonographic evaluation include the lack of ionizing radiation, the noninvasive nature of the examination, focused evaluation correlated with the specific site of pain, multiplanar capability, and utility in patients for whom magnetic resonance imaging (MRI) is contraindicated. The ability to visualize the microanatomy of tendons, ligaments, nerves, and muscles is also an advantage over MRI. Moreover, ultrasound is generally readily accessible and of lower cost than MRI. Ultrasound is less suited for the evaluation of internal derangement. Certain structures that are exquisitely evaluated by MRI, including the menisci, cruciate ligaments, bone marrow, and articular cartilage, are suboptimally evaluated by sonography. This article reviews the structures and pathological processes for which ultrasound has been shown useful, emphasizing appropriate technique and normal anatomy, appearance of pathological processes, and advantages and limitations of sonographic evaluation.