PERFORMANCE EVALUATION OF METHODS FOR TWO-DIMENSIONAL DISPLACEMENT AND STRAIN ESTIMATION USING ULTRASOUND RADIO FREQUENCY DATA
PERFORMANCE EVALUATION OF METHODS FOR TWO-DIMENSIONAL DISPLACEMENT AND STRAIN ESTIMATION USING ULTRASOUND RADIO FREQUENCY DATA
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DOI：
10.1016/j.ultrasmedbio.2008.11.002
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发表时间：
2009-05-01
影响因子：
2.9
通讯作者：
de Korte, Chris L.
中科院分区：
文献类型：
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作者：
Lopata, Richard G. P.;Nillesen, Maartje M.;de Korte, Chris L.
在弹性成像中，介绍了几种基于原始频率(RF)数据和散斑跟踪的二维应变成像方法。尽管轴向应变成像以弹性图信噪比(SNRE)和弹性图信噪比(CNRe)为指标的精确度和病变可探测性已被广泛报道，但对横向精确度的分析仍然缺乏。本文利用模拟数据和模型实验对不同的二维相关射频应变估计方法和基于包络的应变估计方法的性能进行了评估。除了采用窗口大小和插值法进行亚样本位移估计外，还考察了相关技术的影响。利用模拟位移和实测位移的差值SNRE和CNRe来评估测量的位移和应变的精度和对比度。一般来说，对于窗口尺寸超过应变估计理论上限的包络数据，倾向于采用从粗略到精细的二维位移估计方法。使用2-D窗口的RF数据导致了更好的轴向和横向位移估计，而不是基于1-D RF或基于包络的技术。通过互相关函数(CCF)拟合预定义形状来获得亚样本横向位移估计，得到的结果类似于在横向上对RF数据进行上采样所获得的结果。使用CCF模型是有利的，因为减少了计算时间。在一定的应变范围内(0.5%到5.0%)，窗口的局部对准和拉伸(Recrelation)导致轴向和侧向应变估计的SNRE分别增加2-17和6-7分贝。对于一个模拟的非均匀体模(外加2.0%应变)，测得的轴向和横向信噪比分别为29.2和20.2d B，而信噪比分别为50.2 d B和31.5 d B。对于实验数据，SNRE(轴向：28.5db；侧向：17.5db)和CNRe(轴向：39.3db；侧向：31db)较低。总而言之，在精细尺度上使用射频数据是一种从粗到精的方法。使用二维抛物线插值法可以获得次样本位移估计。再相关技术，如局部对齐和拉伸，在两个方向上增加SNRE和CNRe。(电子邮件：r.lopata@cukz.umcn.nl)(C)2009年世界医学和生物学超声联合会。
In elastography, several methods for 2-D strain imaging have been introduced, based on both raw frequency (RF) data and speckle-tracking. Although the precision and lesion detectability of axial strain imaging in terms of elastographic signal-to-noise ratio (SNRe) and elastographic contrast-to-noise ratio (CNRe) have been reported extensively, analysis of lateral precision is still lacking. In this paper, the performance of different 2-D correlation RF- and envelope-based strain estimation methods was evaluated using simulation data and phantom experiments. Besides window size and interpolation methods for subsample displacement estimation, the influence of recorrelation techniques was examined. Precision and contrast of the measured displacements and strains were assessed using the difference between modeled and measured displacements, SNRe and CNRe. In general, a 2-D coarse-to-fine displacement estimation method is favored, using envelope data for window sizes exceeding the theoretical upper bound for strain estimation. Using 2-D windows of RF data resulted in better displacement estimates for both the axial and lateral direction than 1-D RF-based or envelope-based techniques. Obtaining subsample lateral displacement estimates by fitting a predefined shape through the cross-correlation function (CCF) yielded results similar to those obtained with up-sampling of RF data in the lateral direction. Using a CCF model was favored because of the decreased computation time. Local aligning and stretching of the windows (recorrelation) resulted in an increase of 2-17 and 6-7 dB in SNRe for axial and lateral strain estimates, respectively, over a range of strains (0.5 to 5.0%). For a simulated inhomogeneous phantom (2.0% applied strain), the measured axial and lateral SNRes were 29.2 and 20.2 dB, whereas the CNRes were 50.2 dB and 31.5 dB, respectively. For the experimental data, lower SNRe (axial: 28.5 dB; lateral: 17.5 dB) and CNRe (axial: 39.3 dB; lateral: 31 dB) were found. In conclusion, a coarse-to-fine approach is favored using RF data on a fine scale. The use of 2D parabolic interpolation is favored to obtain subsample displacement estimates. Recorrelation techniques, such as local aligning and stretching, increase SNRe and CNRe in both directions. (E-mail: r.lopata@cukz.umcn.nl) (C) 2009 World Federation for Ultrasound in Medicine & Biology.