Abstract
BackgroundConventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative MRI sequences. We aimed to examine a threshold-based fat quantification method in the supraspinatus muscle on standard T1-weighted MR images and compare the threshold-based method with Goutallier grades and MR spectroscopy.MethodsWe retrospectively examined 38 symptomatic patients, who underwent T1 and T2-weighted fast spin-echo MR imaging and a single voxel spin-echo MR spectroscopy. The supraspinatus muscle and fossa were manually segmented in T1-weighted sagittal images and clustering-based thresholding was applied to quantify the fat fractions in the segmented areas using custom MATLAB software. Threshold-based fat fractions were compared with the Goutallier grades and MR spectroscopy fat/water ratios. A one-way analysis of variance and Pearson correlation were tested in the MATLAB software.ResultsInter-observer reliability of threshold-based fat fractions for the supraspinatus muscle and fossa were 0.977 and 0.990 respectively, whereas the reliability of the Goutallier grading was 0.798. Threshold-based fat fractions in the supraspinatus fossa were significantly different between various Goutallier grades (one-way ANOVA, p < 0.001). Threshold-based fat fractions in the supraspinatus muscle strongly correlated with the MR spectroscopy fat/water ratio (Pearson correlation R-square = 0.83).ConclusionsThreshold-based fat quantification on standard T1-weighted MR images was highly reliable and produced comparable results to conventional Goutallier grades and MR spectroscopy fat/water ratios and could serve as an alternative method for accurate fat quantification in rotator cuff muscles.
Highlights
Conventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative magnetic resonance imaging (MRI) sequences
We retrospectively examined the supraspinatus muscle on MR images of symptomatic patients from the outpatient shoulder clinic to evaluate the rotator cuff tendon status as well as muscle quality for preoperative evaluation
Reliability of Goutallier classification The inter-observer reliability of the Goutallier grades between the three raters was fairly good with an interclass correlation coefficient (ICC) of 0.80
Summary
Conventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative MRI sequences. Surgical repairs of torn rotator cuff muscles must be considered prior to the progression of severe fatty infiltration or atrophy of the muscles [4,5,6]. Various computed tomography (CT) and magnetic resonance imaging (MRI) techniques have been introduced to non-invasively examine the degree of fatty degeneration of the rotator cuff muscles [7]. The Goutallier grades have been reported to correlate with the severity of fatty infiltration in the rotator cuff muscles, their inconsistent intra-observer and inter-observer agreements need to be improved for use in accurate clinical diagnostic applications [11,12,13,14]
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