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Effect of ensemble averaging on amplitude and feature variabilities of Doppler spectrograms recorded in the lower
L Allard1, Y E Langlois, L G Durand
1Laboratoire de Génie Biomédical, Institut de Recherches Cliniques de Montréal, Québec, Canada.
Insights
Averaging Doppler blood flow signals in lower limb arteries over ten cardiac cycles sufficiently reduces variability. This method enhances diagnostic feature discrimination for various stenosis categories in iliac and superficial femoral arteries.
Area of Science:
- Vascular Ultrasound
- Signal Processing
- Medical Diagnostics
Background:
- Doppler ultrasound is crucial for assessing lower limb arterial blood flow.
- Variability in Doppler signals can complicate stenosis diagnosis.
- Optimizing signal averaging is key to improving diagnostic accuracy.
Purpose of the Study:
- To analyze the impact of averaging Doppler signals on amplitude and feature variability.
- To determine the optimal number of cardiac cycles for averaging Doppler spectrograms.
- To evaluate how averaging affects the ability to differentiate stenosis categories.
Main Methods:
- Doppler signals from 41 iliac and 35 superficial femoral arteries were recorded.
- Signals were averaged across 1 to 15 cardiac cycles.
- Variability indices and diagnostic features were quantified, and t-test analyses were performed.
Main Results:
- Amplitude and feature variability decreased exponentially with averaging.
- Averaging 5-10 cardiac cycles offered the best discriminant power for stenosis.
- Averaging beyond ten cycles provided minimal additional benefit.
Conclusions:
- Averaging Doppler spectrograms over ten cardiac cycles is sufficient for lower limb artery analysis.
- This optimized averaging reduces signal variability and improves diagnostic feature reliability.
- The findings support standardized signal processing for enhanced vascular ultrasound accuracy.
Abstract:
The objective of the present study was to analyse the effect of averaging Doppler blood flow signals in lower limb arteries on amplitude and feature variabilities. Doppler signals recorded in 41 iliac and 35 superficial femoral arteries having different categories of stenosis were averaged over 1-15 cardiac cycles. Based on the relative decreasing rate of an index of variability, results indicated that amplitude variability of the spectrograms was exponentially reduced to 30, 6 and 1 per cent when averaging five, ten and 15 cardiac cycles, respectively. Nine diagnostic features were extracted from Doppler spectrograms and their variations from one cardiac cycle to the next quantified. Based on the relative decreasing rate of these variations, results indicated that feature variability was exponentially reduced to 30, 4 and 1 per cent when averaging five, ten and 15 cardiac cycles, respectively. The effect of averaging on the discriminant power of the features to separate the different categories of stenosis was also investigated by performing t-test analyses. Results showed that averaging between five and ten cardiac cycles provided the better discriminant power for most cases, whereas averaging over more than ten cardiac cycles was of little benefit. Based on the spectral analysis technique used in the present study, we conclude that averaging over ten cardiac cycles is sufficient for the analysis of Doppler spectrograms recorded in the lower limbs.