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首页> 外文期刊>IEEE Transactions on Medical Imaging >Improved Contrast-Enhanced Power Doppler Using a Coherence-Based Estimator
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Improved Contrast-Enhanced Power Doppler Using a Coherence-Based Estimator

机译：使用基于相干的估计器改进的对比度增强功率多普勒

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摘要

While plane-wave imaging can improve the performance of power Doppler by enabling much longer ensembles than systems using focused beams, the long-ensemble averaging of the zero-lag autocorrelation R(0) estimates does not directly decrease the mean noise level, but only decreases its variance. Spatial variation of the noise due to the time-gain compensation and the received beamforming aperture ultimately limits sensitivity. In this paper, we demonstrate that the performance of power Doppler imaging can be improved by leveraging the higher lags of the autocorrelation [e.g., R(1), R(2),...] instead of the signal power (R(0)). As noise is completely uncorrelated from pulse-to-pulse while the flow signal remains correlated significantly longer, weak signals just above the noise floor can be made visible through the reduction of the noise floor. Finally, as coherence decreases proportionally with respect to velocity, we demonstrate how signal coherence can be targeted to separate flows of different velocities. For instance, we show how long-time-range coherence of microbubble contrast-enhanced flow specifically isolates slow capillary perfusion (as opposed to conduit flow).
机译：虽然平面波成像可以通过比使用聚焦光束的系统进行更长的集成来提高功率多普勒的性能，但零延迟自相关R（0）估计值的长集合平均不会直接降低平均噪声水平，而只是减小其方差。由于时间增益补偿和接收到的波束成形孔径而导致的噪声空间变化最终会限制灵敏度。在本文中，我们证明可以通过利用自相关的较高滞后[例如，R（1），R（2），...]代替信号功率（R（0,0）来提高功率多普勒成像的性能。 ））。由于噪声与脉冲之间是完全不相关的，而流量信号之间的相关时间则要长得多，因此通过降低本底噪声可以使在本底噪声之上的微弱信号可见。最后，随着相干性相对于速度成比例地降低，我们证明了信号相干性可以如何针对不同速度的分离流。例如，我们显示了微气泡对比增强流的长时间范围内的连贯性如何特别隔离缓慢的毛细管灌注（与导管流动相反）。

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