Repeatability of chemical-shift-encoded water-fat MRI and diffusion-tensor imaging in lower extremity muscles in children.
OBJECTIVE
The purpose of this study was to assess the repeatability of water-fat MRI and diffusion-tensor imaging (DTI) as quantitative biomarkers of pediatric lower extremity skeletal muscle.


METHODS
MRI at 3 T of a randomly selected thigh and lower leg of seven healthy children was studied using water-fat separation and DTI techniques. Muscle-fat fraction, apparent diffusion coefficient (ADC), and fractional anisotropy (FA) values were calculated. Test-retest and interrater repeatability were assessed by calculating the Pearson correlation coefficient, intraclass correlation coefficient, and Bland-Altman analysis.


RESULTS
Bland-Altman plots show that the mean difference between test-retest and interrater measurements of muscle-fat fraction, ADC, and FA was near 0. The correlation coefficients and intraclass correlation coefficients were all between 0.88 and 0.99 (p < 0.05), suggesting excellent reliability of the measurements. Muscle-fat fraction measurements from water-fat MRI exhibited the highest intraclass correlation coefficient. Interrater agreement was consistently better than test-retest comparisons.


CONCLUSIONS
Water-fat MRI and DTI measurements in lower extremity skeletal muscles are objective repeatable biomarkers in children. This knowledge should aid in the understanding of the number of participants needed in clinical trials when using these determinations as an outcome measure to noninvasively monitor neuromuscular disease.
1 Department of Radiology, Children's Hospital Los Angeles, MS #81, 4650 Sunset Blvd, Los Angeles, CA 90027.
Skorn
S
Ponrartana
Kristine E
KE
Andrade
Tishya A L
TA
Wren
Leigh
L
Ramos-Platt
Houchun H
HH
Hu
Stefan
S
Bluml
Vicente
V
Gilsanz
D000273:Adipose Tissue / Q000033:anatomy & histology* / Q000378:metabolism; D000293:Adolescent; D001834:Body Water / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D035002:Lower Extremity / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000378:metabolism; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity