Fig 1.
A 14-year-old boy with obesity (body mass index, 28.9 kg/m2) and fatty liver.
From the liver MRI, (A) fat fraction of the liver (18%) was obtained from oval or circular region-of-interest (ROI, yellow circle) in the right lobe on the fat map. (B) The ROIs (yellow circles) for paraspinal muscle fat fraction were drawn bilaterally at the level of mid L2 and the mean value was 3.2% in this case. (C) In order to measure the psoas muscle area (PMA), free hand ROIs (yellow lines) were drawn at the level of mid L3 on T2-weighted axial images. The PMA was 1197.7 mm2 and the z-score of PMA was -2.56 in this patient.
Fig 2.
A 7-year-old boy with normal body mass index (18.3 kg/m2) and fatty liver.
From the liver MRI, (A) fat fraction of the liver was 18.5%. (B) The mean paraspinal muscle fat fraction of the two circles was 2.1%. (C) The PMA was 265.1 mm2 and the z-score of PMA was -4.3 in this patient.
Table 1.
Demographics and group comparisons.
Table 2.
Correlation between muscle condition and liver fat or body mass index.
Fig 3.
Box plots and representative images for the group comparison of sex and body mass index (BMI) groups.
Based on BMI, 47 patients were normal, 29 were overweight, and 56 were obese. (A) Z-score of PMA was increased according to the increased BMI groups. Male patients had higher z-score of PMA than did female patients in all BMI groups. (B) The paraspinal muscle fat fraction also showed increasing tendency according to the increased BMI groups; however, the sex difference was not definite. (C) A 13-year-old female with obesity (BMI, 32.4 kg/m2) and fatty liver (10.9%) had 5.2% paraspinal muscle fat and 595.2 mm2 PMA (z-score, -3.33). (D) A 15-year-old female without obesity (BMI, 15.8 kg/m2) nor fatty liver (3%) had 1.9% paraspinal muscle fat and 355.9 mm2 PMA (z-score, -4.48).
Fig 4.
Scatter plots for the correlations between body mass index (BMI) z-score and psoas muscle area z-score or paraspinal muscle fat.
BMI z-score has positive linear correlations with (A) z-score of PMA (β = 0.289, p < 0.001) and (B) paraspinal muscle fat (β = 0.218, p = 0.016). The dot color means the BMI group as normal with blue, overweight with red, and obese with green.
Table 3.
Regression analyses for psoas muscle z-score in consideration with other variables.