Undoubtedly, highly valuable information about vascular anomalies is attained by the examination of the blood flow profile. The chief drawback of the conventional medical ultrasound in preparation of the blood periodogram is the measurement system shortcoming at the beam to flow angles near 90°. Recently, a method based on transverse oscillation (TO) approach, known as "Fourth-order estimation", has been developed to directly estimate the transverse power spectral density (PSD) of the fully transverse blood flow. One of the basic requirements to accomplish acceptable PSDs by this technique is the sufficiently large observation window. In this paper, two adaptive approaches for efficient estimation of the velocity spectrum of a fully transverse flow by a limited observation window length are described. The first proposed adaptive approach is based on the minimum variance adaptive spectral estimation in combination with the well-known TO technique (TO-MV). Then, by exploiting the eigenspace separation of the observed data to eliminate the contribution of the undesired components, the second technique (TO-EIBMV) is developed. The approaches are validated using Field II simulations for pulsating flow. The proposed methods are tested and compared to the conventional TO transverse spectral estimator by metrics of relative standard deviation (RSD) and relative bias (RB). One of the main achievements is the decrement of the required data samples for spectrogram estimation, which leads to a better temporal resolution. Moreover, for the analyzed adaptive techniques, the robustness of the estimation results for the beam to flow angles of 60-90° and vessel depths ranging from 20 mm to 60 mm are investigated.

中文翻译：

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医学超声中的自适应横向血流速度估计：模拟研究

毫无疑问，通过检查血流剖面可以获得关于血管异常的非常有价值的信息。常规医学超声在制备血液周期图时的主要缺点是测量系统的缺点是波束与流动角度接近 90°。最近，已经开发了一种基于横向振荡 (TO) 方法的方法，称为“四阶估计”，用于直接估计完全横向血流的横向功率谱密度 (PSD)。通过这种技术实现可接受的 PSD 的基本要求之一是足够大的观察窗口。在本文中，描述了通过有限的观察窗长度有效估计完全横向流的速度谱的两种自适应方法。第一种提出的自适应方法是基于最小方差自适应谱估计结合众所周知的 TO 技术 (TO-MV)。然后，通过利用观测数据的特征空间分离来消除不需要的分量的贡献，开发了第二种技术（TO-EIBMV）。使用 Field II 模拟脉动流对这些方法进行了验证。通过相对标准偏差 (RSD) 和相对偏差 (RB) 的度量，对所提出的方法进行了测试并与传统的 TO 横向光谱估计器进行了比较。主要成就之一是减少了频谱图估计所需的数据样本，从而获得了更好的时间分辨率。此外，对于分析的自适应技术，