A method for estimating vector velocities using transverse oscillation (TO) combined with directional beamforming is presented. Directional Transverse Oscillation (DTO) is selfcalibrating, which increase the estimation accuracy and finds the lateral oscillation period automatically. A normal focused field is emitted and the received signals are beamformed in the lateral direction transverse to the ultrasound beam. A lateral oscillation is obtained by having a receive apodization waveform with two separate peaks. The IQ data are obtained by making a Hilbert transform of the directional signal, and a modified TO estimator can be used to find both the lateral and axial velocity. The approach is self-calibrating as the lateral oscillation period directly is estimated from the directional signal through a Fourier transform. The approach was implemented on the SARUS scanner using a BK Medical 8820e transducer with a focal point at 105.6 mm (F#=5) for Vector Flow Imaging (VFI). A 6 mm radius tube in a circulating flow rig was scanned and the parabolic volume flow of 112.7 l/h (peak velocity 0.55 m/s) measured by a Danfoss Magnetic flow meter for reference. Velocity estimates for DTO are found for 32 emissions at a 90 degrees beam-to-flow angle at a vessel depth of 30 mm. The standard deviation (SD) drops from 9.14% for TO to 5.4%, when using DTO. The bias is -5.05% and the angle is found within +/- 3.93 degrees. At 70 mm a relative SD of 7% is obtained, the bias is -1.74%, and the angle is found within +/- 2.6 degrees showing a low bias across depths.
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机译:提出了一种结合横向振荡(TO)和定向波束形成的矢量速度估计方法。方向横向振荡(DTO)是自校准的,可以提高估计精度并自动找到横向振荡周期。发射正常的聚焦场,并且在垂直于超声波束的横向方向上对接收到的信号进行波束成形。通过使接收变迹波形具有两个单独的峰值,可获得横向振荡。 IQ数据是通过对方向信号进行希尔伯特(Hilbert)变换而获得的,而经过修改的TO估计器可用于查找横向和轴向速度。该方法是自校准的,因为通过傅立叶变换直接从方向信号中估计出横向振荡周期。该方法是在SARUS扫描仪上使用BK Medical 8820e换能器实现的,换能器的焦点在105.6毫米(F#= 5)处,用于矢量流成像(VFI)。扫描循环流动装置中一个半径为6 mm的管,并用Danfoss电磁流量计测量112.7 l / h的抛物线体积流量(峰值速度0.55 m / s)作为参考。在30 mm的容器深度下,以90度的束流角,对32种排放量发现了DTO的速度估算值。使用DTO时,标准偏差(SD)从TO的9.14%降至5.4%。偏差为-5.05%,角度为+/- 3.93度。在70毫米处,相对SD为7%,偏差为-1.74%,并且角度在+/- 2.6度以内,表明整个深度的偏差较小。
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