Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, USA.
Structural Biology Brussels, SBB, Vrije Universiteit Brussel, 1050 Brussels, Belgium.
Soft Matter. 2016 Aug 17;12(33):6926-36. doi: 10.1039/c6sm00946h.
We put forth an algorithm to track isolated micron-size solid and liquid particles that produce time-dependent asymmetric intensity patterns. This method quantifies the displacement of a particle in the image plane from the peak of a spatial cross-correlation function with a reference image. The peak sharpness results in subpixel resolution. We demonstrate the utility of the method for tracking liquid droplets with changing shapes and micron-size particles producing images with exaggerated asymmetry. We compare the accuracy of diffusivity determination with particles of known size by this method to that by common tracking techniques and demonstrate that our algorithm is superior. We address several open questions on the characterization of diffusive behaviors. We show that for particles, diffusing with a root-mean-square displacement of 0.6 pixel widths in the time between two successive recorded frames, more accurate diffusivity determinations result from mean squared displacement (MSD) for lag times up to 5 time intervals and that MSDs determined from non-overlapping displacements do not yield more accurate diffusivities. We discuss the optimal length of image sequences and demonstrate that lower frame rates do not affect the accuracy of the estimated diffusivity.
我们提出了一种算法来跟踪产生时变非对称强度模式的孤立微米级固液颗粒。该方法通过与参考图像的空间互相关函数峰值来量化图像平面中颗粒的位移。峰值的锐度导致亚像素分辨率。我们展示了该方法在跟踪具有变化形状的液滴和产生图像的微米级颗粒方面的实用性，这些图像具有夸张的非对称性。我们将通过该方法确定已知大小的颗粒的扩散率的准确性与常见的跟踪技术进行比较，并证明我们的算法更优越。我们解决了关于扩散行为特征描述的几个开放性问题。我们表明，对于在连续两帧记录之间以均方根位移 0.6 个像素宽度扩散的颗粒，对于滞后时间高达 5 个时间间隔的平均平方位移 (MSD)，可以得到更准确的扩散率，并且不重叠位移确定的 MSD 不会产生更准确的扩散率。我们讨论了图像序列的最佳长度，并证明较低的帧率不会影响估计扩散率的准确性。
