ECG-triggered retrospective colour flow imaging

Colour flow imaging systems estimate flow velocities by measuring the phase/time shift between backscattered signals. Using a high-frequency single-element transducer, colour flow imaging of blood velocities has been accomplished in mice by sweeping the transducer over a region of interest. This technique, however, has limitations: tissue clutter artifacts are induced by the sweep-velocity; spatio-temporal artifacts occur when visualizing pulsatile flow; the accuracy of flow velocity estimation is limited. To overcome these limitations, a retrospective colour flow imaging technique (RCFI) has been developed, using the ECG to trigger the acquisition of M-mode data at successive lateral positions of the transducer, followed by retrospective reconstruction of colour flow images. This technique was validated using a phantom with a sinusoidally varying velocity profile, and compared to the swept-scan technique in mouse carotid arteries.