Appropriate Window Function and Window Length in Multifrequency Velocity Estimator for Rapid Motion and Locality of Layered Myocardium
Appropriate Window Function and Window Length in Multifrequency Velocity Estimator for Rapid Motion and Locality of Layered Myocardium
复制标题
多频速度估计器中分层心肌快速运动和局部性的适当窗函数和窗长度
DOI：
10.1109/tuffc.2022.3153048
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Kanai Hiroshi
中科院分区：
文献类型：
--
作者：
Obara Yu;Mori Shohei;Arakawa Mototaka;Kanai Hiroshi
心壁具有多层结构，在射血和快速充盈期间快速移动。每个心肌层的局部应变率 (SR) 测量有助于准确、灵敏地评估心肌功能。然而，由于最大可检测速度受到正交频率的限制，使用单频相位差的基于超声的速度估计器无法实现这些测量。我们之前提出了一种使用多频相位差的速度估计器来提高最大可检测速度。然而，这种改进受到代表速度估计局部性的空间离散傅里叶变换（DFT）窗口长度的影响。在本文中，我们从理论上描述了缩短窗口会增加不同频率分量之间的干扰并降低最大可检测速度。通过模拟和水箱实验证实了最大可检测速度和窗口长度之间的权衡。在权衡之下，之前研究中使用的汉宁窗并不总是适合速度的局部测量，有时超过 100 mm，具体取决于受试者、超声波束到心壁的方向和心动周期。在短窗体内测量中，具有大平坦部分的Tukey窗具有高频分辨率并改善了窗信号两端的不连续性，适合测量最大速度。这项研究提供了使用具有适当窗函数和窗长度的多频速度估计器对每个心肌层进行局部测量的潜力。
The heart wall has a multilayered structure and moves rapidly during ejection and rapid filling periods. Local strain rate (SR) measurements of each myocardial layer can contribute to accurate and sensitive evaluations of myocardial function. However, ultrasound-based velocity estimators using a single-frequency phase difference cannot realize these measurements owing to insufficient maximum detectable velocity, which is limited by a quadrature frequency. We previously proposed a velocity estimator using multifrequency phase differences to improve the maximum detectable velocity. However, the improvement is affected by a spatial discrete Fourier transform (DFT) window length that represents the locality of the velocity estimation. In this article, we theoretically describe that shortening the window increases the interference between different frequency components and decreases the maximum detectable velocity. The tradeoff between the maximum detectable velocity and the window length was confirmed through simulations and a water-tank experiment. Under the tradeoff, the Hanning window, which was used in previous studies, is not always appropriate for the local measurement of the velocity, which sometimes exceeds 100 mmdepending on the subject, direction of the ultrasound beam to the heart wall, and cardiac periods. In thein vivomeasurement with the short window, the Tukey window with a large flat part that has a high-frequency resolution and ameliorates the discontinuity at both edges of the windowed signal was appropriate to measure the maximum velocity. This study offers the potential for local measurements of each myocardial layer using the multifrequency velocity estimator with the appropriate window function and window length.