Introduction
Materials and methods
Subjects and MRI examination schedule
MRI sequence selection
MRI acquisition
Fat fraction measurement
T1-relaxometry
T2-relaxometry
B1 mapping
Magnetisation transfer ratio
ROI analysis
Statistics
Results
Data quality
Individual muscle values
Scan-rescan and inter-observer reliability
Measure | 1st scan group (mean ± SD) | 2nd scan group (mean ± SD) | ICC | Limits of agreement |
n
|
---|---|---|---|---|---|
Thigh level—mean across all ROIs for each subject
| |||||
Fat-Fraction (%) | 1.36 ± 0.50 | 1.25 ± 0.58 | 0.91 | -0.51 to +0.28 | 14 |
T1 (ms) | 1,290 ± 32 | 1,288 ± 30 | 0.65 | -39 to +35 | 14 |
T2 (ms) | 42.01 ± 2.28 | 42.19 ± 2.29 | 0.94 | -1.47 to +1.83 | 14 |
MTR (p.u.) | 32.23 ± 1.40 | 32.25 ± 1.19 | 0.87 | -1.63 to +1.67 | 14 |
Calf level—mean across all ROIs for each subject
| |||||
Fat-Fraction (%) | 1.54 ± 0.65 | 1.30 ± 0.56a
| 0.89 | -0.58 to +0.08 | 15 |
T1 (ms) | 1,276 ± 66 | 1,283 ± 56 | 0.62 | -100 to +114 | 13 |
T2 (ms) | 39.89 ± 1.75 | 40.23 ± 2.14 | 0.83 | -1.84 to +2.54 | 15 |
MTR (p.u.) | 32.80 ± 0.57 | 32.91 ± 0.44 | 0.69 | -0.67 to +0.89 | 14 |
Thigh level—individual ROI values
| |||||
Fat-Fraction (%) | 1.32 ± 0.87 | 1.20 ± 0.82a
| 0.76 | -1.25 to +1.01 | 254 |
T1 (ms) | 1,282 ± 88 | 1,286 ± 81 | 0.79 | -103 to +111 | 190 |
T2 (ms) | 41.90 ± 3.17 | 42.11 ± 3.27 | 0.83 | -3.43 to +3.83 | 255 |
MTR (p.u.) | 32.35 ± 1.79 | 32.40 ± 1.47 | 0.71 | -2.39 to +2.49 | 224 |
Calf level individual ROI values
| |||||
Fat-Fraction (%) | 1.51 ± 0.93 | 1.21 ± 0.85a
| 0.62 | -1.55 to +0.95 | 166 |
T1 (ms) | 1,271 ± 83 | 1,281 ± 79 | 0.65 | -122 to +142 | 119 |
T2 (ms) | 39.89 ± 2.60 | 40.23 ± 2.92a
| 0.79 | -3.11 to +3.80 | 180 |
MTR (p.u.) | 32.82 ± 1.35 | 32.89 ± 1.03 | 0.65 | -1.9 to +2.04 | 160 |
Measure | 1st observer group (mean ± SD) | 2nd observer group (mean ± SD) | ICC | Limits of agreement |
n
|
---|---|---|---|---|---|
Thigh level—overall mean for each subject
| |||||
Fat fraction (%) | 1.33 ± 0.50 | 1.24 ± 0.41a
| 0.93 | -0.39 to +0.21 | 15 |
T1 (ms) | 1,293 ± 33 | 1,287 ± 34 | 0.95 | -26 to +14 | 15 |
T2 (ms) | 41.97 ± 2.20 | 42.01 ± 2.22 | 0.98 | -0.93 to +1.00 | 15 |
MTR (p.u.) | 32.29 ± 1.37 | 32.34 ± 1.27 | 0.99 | -0.49 to +0.59 | 15 |
Calf level—overall mean for each subject
| |||||
Fat fraction (%) | 1.54 ± 0.65 | 1.51 ± 0.57 | 0.95 | -0.41 to +0.33 | 15 |
T1 (ms) | 1,275 ± 63 | 1,276 ± 66 | 0.99 | -23 to +24 | 14 |
T2 (ms) | 39.89 ± 1.75 | 39.75 ± 1.79 | 0.96 | -1.08 to +0.80 | 15 |
MTR (p.u.) | 32.75 ± 0.57 | 32.84 ± 0.56 | 0.95 | -0.25 to +0.43 | 15 |
Thigh level—individual ROI values
| |||||
Fat fraction (%) | 1.32 ± 0.91 | 1.23 ± 0.91a
| 0.79 | -1.04 to +1.22 | 281 |
T1 (ms) | 1,289 ± 88 | 1,284 ± 94 | 0.93 | -62 to +72 | 221 |
T2 (ms) | 41.96 ± 3.19 | 42.00 ± 3.61 | 0.84 | -3.82 to +3.75 | 280 |
MTR (p.u.) | 32.36 ± 1.80 | 32.34 ± 1.91 | 0.90 | -1.59 to +1.63 | 248 |
Calf level individual ROI values
| |||||
Fat fraction (%) | 1.55 ± 0.97 | 1.50 ± 0.98 | 0.83 | -1.08 to +1.17 | 172 |
T1 (ms) | 1,269 ± 81 | 1,269 ± 81 | 0.95 | -48 to +50 | 138 |
T2 (ms) | 39.89 ± 2.60 | 39.75 ± 2.69 | 0.86 | -2.59 to +2.88 | 180 |
MTR (p.u.) | 32.76 ± 1.36 | 32.83 ± 1.31 | 0.92 | -1.15 to +1.00 | 175 |
Dependence upon age, gender and weight
Thigh | Calf | |||
---|---|---|---|---|
FF | R = 0.58, p = 0.001 | R = 0.42, p < 0.05 | ||
Co-eff |
p
| Co-eff |
p
| |
Constant | -0.942 | 0.150 | 0.573 | 0.399 |
Gender | -0.125 | 0.597 | -0.329 | 0.174 |
Age |
0.016
|
0.026
|
0.014
|
0.047
|
Weight |
0.025
|
0.003
| 0.008 | 0.374 |
T1
| R = 0.50, p = 0.01 | R = 0.43, p = 0.10 | ||
Co-eff |
p
| Co-eff |
p
| |
Constant | 1356.9 | 0.000 | 1278.0 | 0.000 |
Gender | 15.98 | 0.189 | 31.34 | 0.051 |
Age | -0.519 | 0.149 | -0.132 | 0.770 |
Weight |
-0.858
|
0.035
| -0.366 | 0.468 |
T2
| R = 0.60, p < 0.001 | R = 0.57, p = 0.001 | ||
Co-eff |
p
| Co-eff |
p
| |
Constant | 34.44 | 0.000 | 34.97 | 0.000 |
Gender | -0.163 | 0.839 | -1.175 | 0.142 |
Age |
0.074
|
0.003
|
0.067
|
0.006
|
Weight |
0.073
|
0.009
| 0.049 | 0.064 |
MTR | R = 0.75, p < 0.001 | R = 0.61, p < 0.001 | ||
Co-eff |
p
| Co-eff |
p
| |
Constant | 35.90 | 0.000 | 33.707 | 0.000 |
Gender |
-0.878
|
0.000
| 0.164 | 0.485 |
Age |
-0.029
|
0.000
|
-0.032
|
0.000
|
Weight |
-0.030
|
0.000
| -0.002 | 0.789 |
T1 | T2 | MTR | |
---|---|---|---|
Calf
| |||
Dixon FF | -0.28 | 0.61 | -0.30 |
T1
| -0.18 | 0.42 | |
T2
| -0.47 | ||
Thigh
| |||
Dixon FF | -0.42 | 0.62 | -0.41 |
T1
| -0.21 | 0.48 | |
T2
| -0.51 |