Hybrid Technology Fusion MRI/US and Sonoelastography in Diagnosis of Fatty Degeneration and Atrophy of Supraspinatus Muscle of the Shoulder

Abstract

Evaluation of the rotator cuff muscles is of value for surgical indications and successful postoperative prognosis. Ultrasound is widely used for detection of rotator cuff tears, but it’s role in evaluation of the rotator cuff muscles is not yet defined. A new method Fusion MRI/US with elastography is able to show differences in tissue stiffness, and a simultaneous combination of two methods helps to overcome limitations from US – narrow field of view, and from MRI – impossibility for real time examination and low space resolution.Purpose.To investigate diagnostic performance and interobserver reliability of US elastography and to study possibilities of Fusion MRI/US technique in grading fatty degeneration and atrophy of the supraspinatus muscle.Materials and methods.72 patients from 128 with shoulder pain and disability with written diagnostic confirm were specially selected for the study with US elastography and MRI and 29 patients were enrolled for Fusion MRI/US study. Oblique sagittal scans through the supraspinatus muscle were performed during US elastography study in the standard manner for comparance with MRI. The amount of fatty degeneration was graded according to the modified Goutallier five-point scale, with use of a 3-point scale – with US elastography. US results for grade of atrophy and fatty degeneration were retrospectively reviewed by 2 blinded to each other results experts. Sensitivity and interobserver reliability was estimated.Results.The sensitivity of standard US in comparance to US elastography in assessment of muscle atrophy with the reference to MRI was 53% and 76%, respectively. The sensitivity of US and US elastography increased with increasing of the grade of muscle atrophy. The sensitivity of US and US elastography in detection of fatty degeneration was slightly better 65% and 85%, respectively. US elastography were more sensitive in evaluation of fatty degeneration in full thickness than in partial thickness rotator cuff tears. In all cases of full thickness tears US with elastography had a 100% sensitivity in assessment of atrophy and fatty degeneration in the reference to MRI. While in partial tears the sensitivity decreased to 66%. The agreement between MRI and US elastography for the grade of fatty degeneration of the supraspinatus was substantial (kappa = 0.78). The interobserver reliability for US was fair (kappa = 0.41), and for US elastography substantial (kappa=0,71).Conclusion. Sonoelastography helps to increase the diagnostic performance of US in identifying and grading fatty degeneration and atrophy of the supraspinatus. US with elastography can be used as a primary modality for fatty changes and atrophy of the supraspinatus.