StaBle: Staggered PRF With DouBle Transmission for Increasing the Velocity Limit of High-Frame-Rate Vector Doppler Imaging

Figures

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  FIGURE 1.. Multi-angle Doppler transmission sequences. a) Sequential angle transmission, b) sequential angle transmission with staggered PRF, c) double transmission, and d) the proposed StaBle transmission scheme.

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  FIGURE 2.. Depiction of dealiasing performed on unmatched net angle (a and b) and matched net angle (a and c). The velocity magnitude estimated from d) the unmatched net angle was erroneous, whereas the estimate from e) the matched net angle was more accurate.

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  FIGURE 3.. Flowchart of the key processing steps to implement StaBle algorithm.

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  FIGURE 4.. Example of the data processing steps of StaBle. The first row displays heavily aliased color Doppler images (saturated colormap) from individual double transmits at PRF1 and PRF2. The second row presents the resolved color Doppler after performing the dealiasing process on each Tx-Rx pair with matching net steering angles. Not every pair is shown in the figure. The third row shows the vector field obtained from the resolved color Doppler using the least-squares estimate.

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  FIGURE 5.. Comparison of the simulated vector field produced by StaBle with varying p/q ratios and the corresponding ideal vector field. a) Global RMSE (blue) and NRMSE (red). b) The velocity magnitude NRMSE as a function of distance from the center. c) The lateral and axial velocity for p/q = 2/3 and p/q = 5/6, with the disks spinning at 95% of their respective maximum extended velocity limit.

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  FIGURE 6.. Simulation of a rotating disk with varying speeds. a) The calculated velocity and the ideal velocity profile analyzed by StaBle using different average window lengths for a) lateral velocity in ROI 1 (magenta in c&d) and b) axial velocity in ROI 2 (yellow in c&d). VDI calculated by StaBle during rapid acceleration at 27 ms, processed with window lengths of c) 32 and d) 64.

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  FIGURE 7.. Examples of VDI obtained from the phantom experiment using various transmission sequences. a) Sequential angle transmission sequence, b) Double Tx, c) double transmission with 3x higher PRF, and d) StaBle. The magenta and yellow circles indicate the ROI for obtaining the velocity profile in the lateral (e) and axial (f) directions, respectively.

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  FIGURE 8.. Mouse left ventricle using different transmission sequences. The top row shows aliasing artifact for color Doppler with double transmission at a) PRF1 and b) PRF2. c) A spectrogram from circle region in PRF1 (a). The unambiguous VDI obtained using StaBle over a cardiac cycle at d) early diastole, e) mid-diastole, and f) systole. The gray circles highlight the region of interest used for vector field quantification. g) The axial and lateral velocity derived from the vector field produced by StaBle. The gap between the two central black dashed lines signifies a discontinuity in the acquisition.