Faculty Collaboration Database

Increased signal in the normal supraspinatus tendon on MR imaging: diagnostic pitfall caused by the magic-angle effect. AJR Am J Roentgenol 1995 Jul;165(1):109-14

Date

07/01/1995

Pubmed ID

7785568

DOI

10.2214/ajr.165.1.7785568

Scopus ID

2-s2.0-0029037689 (requires institutional sign-in at Scopus site)   61 Citations

Abstract

OBJECTIVE: Increased signal intensity within the distal portion of the supraspinatus tendon during MR imaging is a frequent observation even in healthy subjects. This finding has been variously attributed to the presence of fat, muscle, connective tissue, abnormal vascularity, or degenerative changes. More recently, the effect of tendon orientation in the static magnetic field (Bo) has been implicated. It has been shown that tendons at the magic angle of 55 degrees to Bo show markedly increased signal. This study was designed to determine the contribution of the magic-angle effect to the MR signal in the distal portion of the supraspinatus tendon.

SUBJECTS AND METHODS: Five healthy volunteers were imaged in a 1.5-T unit using short TR/TE sequences in standard supine position; they were then reimaged laterally flexed at the waist to reorient the plane of the distal portion of the supraspinatus tendon by approximately 20 degrees relative to Bo. In the second part of the study, three cadaveric shoulders were similarly imaged, first in standard position and then reoriented approximately 35 degrees by simple rotation of the specimen. The supraspinatus tendon was evaluated in each subject by noting the length of the segment with increased signal and the position of this segment relative to the insertion of the tendon on the greater tuberosity. Comparisons were made for each live and cadaveric subject between neutral and rotated positions.

RESULTS: Segments of increased signal changed in length and position for each live and cadaveric subject from the neutral to the reoriented position.

CONCLUSION: Our study suggests that tendon orientation contributes significantly to the presence of increased signal within the supraspinatus tendon, as caused by the magic-angle effect. Failure to recognize this effect may lead to diagnostic inaccuracy when evaluating the rotator cuff on short TR/TE sequences.

Author List

Timins ME, Erickson SJ, Estkowski LD, Carrera GF, Komorowski RA

Author

Scott J. Erickson MD Professor in the Radiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adult
Child
Diagnostic Errors
Female
Humans
In Vitro Techniques
Magnetic Resonance Imaging
Male
Middle Aged
Posture
Rotator Cuff
Shoulder
Tendons