Signal-to-noise ratio (SNR) of flow velocity tracings
| Proximal rest | Distal rest | Distal hyperaemia | Distal occlusion | |
| SNR | 4.4 (2.4–6.6) | 2.8 (1.9–5.3) | 4.3 (2.7–6.3) | 1.0 (0.7–1.8) |
| SNR<2 (%) | 17 | 26 | 12 | 78 |
SNR of peak velocity Doppler signal superposition. Values are given as median and 25th–75th percentiles. The noise floor was defined as the average variance in the superimposed Doppler signals. The best signal quality was observed during hyperaemia. However, in 12% of the cases, the amplitude of the Doppler signal did not exceed two times the noise floor. During occlusion, this criterion was not met in 78% of the Doppler recordings.