Accuracy and reproducibility of a subpixel extended phase correlation method to determine micron level displacements in the heart
Accuracy and reproducibility of a subpixel extended phase correlation method to determine micron level displacements in the heart
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DOI：
10.1016/j.medengphy.2006.01.001
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发表时间：
2007-01-01
影响因子：
2.2
通讯作者：
Gaudette, Glenn R.
中科院分区：
文献类型：
--
作者：
Kelly, Damon J.;Azeloglu, Evren U.;Gaudette, Glenn R.
生长因子或祖细胞。这需要精确的测量技术来确定区域心脏功能。我们之前开发了一种使用相位相关算法确定区域心脏功能的方法。然而，在确定单个心跳的区域功能时，有必要对许多图像之间的位移进行求和。因此，我们采用了一种子像素算法，将相位相关的结果建模为正弦函数，以提高我们技术的准确性。我们将这种方法命名为高密度映射 (HDM)，它可以确定心脏图像中 64 x 64 像素区域的子像素位移。为了确定该技术的准确性和精密度，将心脏的高对比度图像进行了 1、2 或 3 个像素的数字移位。然后对原始图像和移位图像进行四次下采样，从而在原始图像和移位图像之间产生 0.25、0.50 或 0.75 像素移位。数字移位图像中 HDM 的平均精度为 0.06 像素，精度为 0.08 像素。还在数字拉伸图像中评估了 HDM 在变形表征方面的有效性。应变量化误差小于计算应变的 3.5%。在另外一组实验中，使用物理运动而不是数字移位和下采样来确定精度，使用微操纵器将散斑图案移动已知距离，使得捕获的图像之间的位移为 0.5 像素。这些数据显示准确度为 0.09 像素，精确度为 0.02 像素。最后，由于 HDM 用于确定跳动心脏中的区域中风做功指数 (RSW)，因此评估了使用该方法计算 RSW 的可重复性。 RSW 是心室内压力相对于无单位区域面积的积分，其中舒张末期面积标准化为统一，在四颗不同心脏的连续心跳中进行评估。 RSW 的平均标准偏差为 0.098 mmHg。不确定性分析确定 RSW 的最大误差为 +/- 0.41 mmHg，大约为测量的生物变异性的三分之二。这些数据证明了 HDM 能够准确、可重复地测量跳动心脏的位移和区域功能。 (c) 2006 年 IPEM。由爱思唯尔有限公司出版。保留所有权利。
growth factors or progenitor cells. This necessitates an accurate measurement technique to determine regional heart function. We have previously developed a method to determine regional heart function using a phase correlation algorithm. However, in determining regional function over a single heartbeat it is necessary to sum displacements between many images. We have therefore incorporated a subpixel algorithm that models the result of phase correlation as a sine function in order to increase the accuracy of our technique. This method, which we have named high density mapping (HDM), determines the subpixel displacement of 64 x 64 pixel regions from images of the heart. To determine the accuracy and precision of the technique, a high contrast image of a heart was digitally shifted 1, 2 or 3 pixels. The original and shifted images were then downsampled four times resulting in 0.25, 0.50 or 0.75 pixel shifts between the original and shifted images. The average accuracy of HDM in the digitally shifted images was 0.06 pixels, with a precision of 0.08 pixels. Effectiveness of HDM in characterization of deformation was also assessed in digitally stretched images. Error in quantification of strain was found to be less than 3.5% of the calculated strain. In an additional set of experiments, in which accuracy was determined using physical motion instead of digital shifting and downsampling, a speckle pattern was displaced by known distances using a micromanipulator, such that the displacement between the captured images was 0.5 pixels. These data demonstrated an accuracy of 0.09 pixels and a precision of 0.02 pixels. Finally, as HDM is used to determine the regional stroke work index (RSW) in beating hearts, the repeatability of using this method to compute RSW was assessed. RSW, the integral of intraventricular pressure with respect to unitless regional area, where end diastolic area was normalized to unity, was assessed in consecutive beats from four different hearts. The average standard deviation of RSW was 0.098 mmHg. Uncertainty analysis determined the maximum error of RSW to be +/- 0.41 mmHg, approximately two-thirds of the measured biologic variability. These data demonstrate the ability of HDM to accurately and reproducibly measure displacement and regional function in the beating heart. (c) 2006 IPEM. Published by Elsevier Ltd. All rights reserved.