Table 2.
Flow, pulsatility index and damping factor and reproducibility of their mean values.
| Artery | Measure | Young subjects | Old subjects | ICC | ||
|---|---|---|---|---|---|---|
| Flow (mL/s) | CoR [mL/s (%)] | Flow (mL/s) | CoR [mL/s (%)] | |||
| FLOW WAVEFORM | ||||||
| MCA | Mean flow | 2.56 ± 0.63 | 0.83 (32) | 1.48 ± 0.30 p = 0.011 |
0.15 (10) | 0.84 (0.47–0.96) |
| Min flow | 1.59 ± 0.49 | 0.96 ± 0.28 p = 0.036 |
||||
| Max flow | 4.19 ± 0.67 | 2.22 ± 0.48 p = 0.001 |
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| LSA | Mean flow | 0.10 ± 0.04 | 0.02 (18) | 0.05 ± 0.03 p = 0.073 |
0.03 (54) | 0.91 (0.70–0.82) |
| Min flow | 0.08 ± 0.03 | 0.04 ± 0.03 p = 0.077 |
||||
| Max flow | 0.12 ± 0.05 | 0.07 ± 0.03 p = 0.087 |
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| DERIVED QUANTITIES | ||||||
| MCA | PI | 1.12 ±0.39 | 0.47 (42) | 0.88 ± 0.22 p = 0.27 |
0.31 (35) | 0.68 (0.13–0.91) |
| LSA | PI | 0.46 ± 0.05 | 0.17 (37) | 0.69 ± 0.22 p = 0.05 |
0.24 (35) | 0.74 (0.25–0.93) |
MCA  LSA |
DF | 2.40 ± 0.76 | 0.98 (41) | 1.31 ± 0.30 p = 0.017 |
0.61 (46) | 0.73 (0.22–0.92) |
All MCA waveform flow measures (mean, min, max) were significantly lower for the older subjects compared to the younger subjects (p < 0.04). For the LSA, there was a comparable trend (p < 0.01). The pulsatility index (PI) was significantly higher for the older subjects for the LSA (p = 0.05), but not for the MCA (p = 0.27). The damping factor (DF) was significantly lower for the older subjects (p = 0.017). Statistical tests (p-values) were performed by a Student's t-test.
Flow notation, mean ± standard deviation; statistical significance is indicated by BOLD type setting. CoR, Coefficient of Repeatability, notation, absolute value (percentage of mean value); ICC, Interclass Correlation Coefficient, notation, value (95% confidence interval).