1. In patients with calcific tendonitis, the addition of susceptibility-weighted imaging (SWI) to conventional shoulder joint magnetic resonance imaging (MRI) sequences provides more robust spatial information to localize calcifications with respect to the rotator cuff tendons without radiation exposure.
2. While combined SWI and MRI improved detection of calcific tendonitis compared to detection by MRI alone, it yielded slightly overestimated calcifications diameters.
Evidence Rating Level: 2 (Good)
Study Rundown: Calcific tendonitis refers to the deposition of calcium—predominantly hydroxyapatite—in a tendon, most often in those of the rotator cuff, causing a great deal of shoulder pain. Calcific tendonitis is typically diagnosed using MRI to locate the calcium deposits while ruling out other shoulder pathologies which may clinically present similarly. SWI is an emerging MRI technique which reflects the magnetic susceptibility of tissues and is much more sensitive to paramagnetic deoxygenated blood, allowing it to characterize not only magnitude-but also phase information in the tissue. Although SWI detection of calcium deposits in other diseases have shown great promise, exploration of this technique in identifying rotator cuff calcifications is not well studied. The present study compared the diagnostic performance of SWI and conventional radiographic evaluations of the rotator cuff in patients with calcific tendonitis. Imaging of the rotator cuff via standard MR sequences and SWI were compared to conventional radiography to identify calcified lesions in patients with suspected calcific tendonitis. The results showed that SWI-detection yielded significantly greater sensitivity in discerning calcifications and resulted in greater inter-observer agreement when compared with conventional MRI sequences. These findings suggest that addition of SWI to standard imaging may advance diagnostic capability and may potentially improve patient care by providing more anatomic detail. Major limitations of this study were that SWI findings were not directly shown with histopathologic examinations and that SWI findings were not examined for correlation to patient symptomatology in any manner. While these findings represent a major step forward for understanding the potential of SWI in calcific tendonitis detection, future studies are warranted before SWI is incorporated in clinical practice to identify calcifications of the rotator cuff.
In-Depth [prospective cohort]: Fifty-four patients clinically suspected of having calcific tendonitis of the rotator cuff were included in the study. Half of the subjects were positive for calcium deposits on radiographic imaging while the other subjects had no calcifications in the shoulder. On traditional radiography, a total of 56 calcifications were detected in the 27 positive subjects, all of whom underwent standard MRI and SWI, including magnitude and phase imaging. On SWI, 55 out of 56 calcifications (98%) were identifiable (95%CI 0.943, 1) with specificity of 96% (95%CI 0.886, 1), while 33 (59%) were identifiable using standard T1- and T2-MRI weighted sequences (95%CI 0.422, 0.758) with a specificity of 67% (95%CI 0.493, 0.847). Calcification diameter was used to assess correlation between imaging methods and SWI was found to be highly correlated with radiography (R2 = 0.90), though lesion diameter was slightly overestimated with SWI (on SWI: 7.6 mm ± 5.4; on radiography: 5.3 mm ± 5.1). Higher interobserver agreement (R2 = 0.99, p < .001; 95%CI 0.989, 0.996) was established on SWI than on standard magnetic resonance sequences (R2 = 0.67, p = .62; 95%CI 0.703, 0.899).
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