Temporal enhancement of 2D color Doppler echocardiography sequences by fragment-based frame reordering and refinement

The goal of this study was to develop an algorithm that enhances the temporal resolution of two-dimensional color Doppler echocardiography (2D CDE) by reordering all the acquired frames and filtering out the frames corrupted by out-of-plane motion and arrhythmia.

The algorithm splits original frame sequence into the fragments based on the correlation with a reference frame. Then, the fragments are aligned temporally and merged into a resulting sequence that has higher temporal resolution. We evaluated the algorithm with 10 animal epicardial 2D CDE datasets of the right ventricle and compared it with the existing approaches in terms of resulting frame rate, image stability and execution time.

We identified the optimal combination of alternatives for each step, which resulted in an increase in frame rate from 14 ± 0.87 to 238 ± 93 Hz. The average execution time was 7.23 ± 0.48 s in comparison with 0.009 ± 0.001 s for ECG gating and 1167.37 ± 587.85 s for flow reordering. Our approach demonstrated a significant (p < 0.01) increase in image stability compared with ECG gating and flow reordering.

This work presents an offline algorithm for temporal enhancement of 2D CDE. Unlike previous frame reordering approaches, it can filter out-of-plane or corrupted frames, increasing the quality of the results, which substantially increases diagnostic value of 2D CDE. It can be used for high-frame-rate intraoperative imaging of intraventricular and valve regurgitant flows and is potentially modifiable for real-time use on ultrasound machines.