Rationale and Objectives
To assess the usefulness of T2*-corrected fat fraction (FF) map from volume-interpolated breathhold examination (VIBE) magnetic resonance (MR) sequence in patients with the rotator cuff pathology.
Materials and Methods
The phantom study was performed to validate the FF maps. Eighty-nine shoulder MR arthrographies were analyzed: (1) divided into three groups namely tendinopathy/normal tendons, partial-thickness tears, and full-thickness tears, and (2) occupation ratio (OR) was measured for muscular atrophy. Uncorrected and T2*-corrected FF maps were reconstructed from the VIBE images. The Pearson correlation test was used to correlate the FFs with ORs. The FF and the OR were compared between groups using the Student t test.
Results
T2*-corrected FF maps could provide a higher correlation than uncorrected FF maps. There were significantly negative correlations between the ORs and the FFs ( P < .01). In the normal and the partial-thickness tear group, the OR did not show a significant difference, although the FF maps showed a significant difference ( P < .01).
Conclusions
This quantitative assessment of the T2*-corrected FF in the rotator cuff muscles was found to be reliable and correlated well with the ORs. The T2*-corrected FF maps could be used for more sophisticated assessments of the fat even in the partial-thickness tear.
Key points:
1. Fat fraction (FF) in the rotator cuff is an important prognostic factor.
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Materials and methods
Phantom Study
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Patient Population
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MR Protocol
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Fat Fraction Maps
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T2*−correctedfatfraction(FF)=F(W+F)×100 T
2
*
-
corrected
fat
fraction
(
FF
)
=
F
(
W
+
F
)
×
100
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Uncorrectedfatfraction(FF)=(IP−OP)(IP+OP)×100 Uncorrected
fat
fraction
(
FF
)
=
(
IP
−
OP
)
(
IP
+
OP
)
×
100
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MRI of Rotator Cuff Tendon Tears
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MRI of Muscle Atrophy
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MRI of Fat Quantification
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Statistical Analysis
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Results
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Table 1
Mean Values and Standard Deviations of the Occupation Ratios and Fat Fractions
Occupation Ratio Uncorrected FF T2*-corrected FF Subscapularis NL/TP 98.11 ± 3.03 9.01 ± 3.52 7.88 ± 1.99 PT 94.71 ± 10.20 11.52 ± 5.24 12.73 ± 7.67 FT 72.25 ± 17.45 20.30 ± 11.28 30.11 ± 22.85 Supraspinatus NL/TP 96.03 ± 5.92 8.14 ± 1.89 6.61 ± 1.81 PT 91.87 ± 9.81 9.74 ± 3.97 7.89 ± 2.41 FT 68.99 ± 22.44 13.19 ± 5.74 22.23 ± 19.43 Infraspinatus NL/TP 98.35 ± 2.13 9.05 ± 2.31 5.81 ± 1.76 PT 92.65 ± 9.59 9.70 ± 3.61 8.74 ± 5.14 FT 68.97 ± 28.38 22.83 ± 7.86 37.71 ± 24.67
FF, fat fraction; FT, full-thickness tear; NL, normal; PT, partial tear; TP, tendinopathy.
The values are represented as mean ± standard deviation.
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Table 2
Pearson Correlations of the Occupation Ratios and Fat Fractions
Correlation Coefficient (95% Confidence Interval) Uncorrected Fat Fraction T2*-corrected Fat Fraction Subscapularis −.65 (−.75 to −.51) ∗ −.86 (−.91 to −.80) ∗ Supraspinatus −.59 (−.71 to −.44) ∗ −.78 (−.86 to −.69) ∗ Infraspinatus −.72 (−.81 to −.60) ∗ −.94 (−.96 to −.91) ∗
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Table 3
Correlations of Occupation Ratios and Fat Fractions with the Tear Sizes (Length/Width) in Patients with Full-thickness Tears
Correlation Coefficient ( P Value) Occupation Ratio Uncorrected FF T2*-corrected FF Tear length Subscapularis −.486 (.356) .769 (.074) .543 (.297) Supraspinatus −.467 (.018) ∗ .639 (<.001) ∗ .766 (<.001) ∗ Infraspinatus .464 (.302) −.378 (.403) −.286 (.556) Tear width Subscapularis −.886 (.033) ∗ .894 (.016) ∗ .943 (.017) ∗ Supraspinatus −.622 (.001) ∗ .534 (.006) ∗ .657 (<.001) ∗ Infraspinatus .0367 (.963) −.140 (.765) .256 (.580)
FF, fat fraction.
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Table 4
Comparisons of Occupation Ratios and Fat Fractions between Groups
Occupation Ratio Uncorrected FF T2*-corrected FF Subscapularis NL/TP and PT .175 .035 .005 ∗ PT and FT .025 ∗ .112 .040 ∗ NL/TP/PT and FT .021 ∗ .072 .024 ∗ Supraspinatus NL/TP and PT .126 .116 .064 PT and FT <.001 ∗ .002 ∗ <.001 ∗ NL/TP/PT and FT <.001 ∗ .005 ∗ <.001 ∗ Infraspinatus NL/TP and PT .321 .598 .338 PT and FT .079 <.001 ∗ .021 ∗ NL/TP/PT and FT .035 ∗ .004 ∗ .014 ∗
FF, fat fraction; FT, full-thickness tear; NL, normal; PT, partial tear; TP, tendinopathy.
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Discussion
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Acknowledgement
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