The purpose of this study is to evaluate the capabilities of MRI on the normal rotator cuff. Four normal shoulders from four volunteers (25-31 y. o., mean 27 y. o. ) were used for imaging. In addition, images from twelve patients (19-80 y. o., mean 43.0 y. o. ) who had no apparent rotator cuff tear were reviewed retrospectively. For anatomical study, these images were compared with corresponding sections of four cadaveric shoulders.
Our previous study has shown that FE image is the best for observing of the normal shoulder, in comparison with other spin echo MR images, such as the Ti weighted, the T2 weighted and the proton density weighted ones. In this study, FE images were taken under Shimadzu 1.0 Tesla superconductive MRI system, using a local flexible coil. They were taken in the oblique coronal (scapular) plane and in the plane transverse to the axis of the supraspinatus muscle (TASS plane).
Two kinds of signal intensities were observed within the normal rotator cuff. Similar findings were observed in all the patients with the exception of an 80 y. o. woman. Their age including the normal volunteers ranged from 19 y. o. to 77 y. o. with a mean age of 38.7 y. o. Comparisons between these images and the cadaveric rotator cuffs showed the good correlation of the images with the anatomical structures. The area of low signal intensity represents the original tendon layer in the rotator cuff, while the comparatively high signal intensity region corresponds to the roughly distributed connective tissue within the rotator cuff. These findings on the images should not be regarded as abnormal.
These results demonstrate that MRI is useful for the observation of the normal rotator cuff.
