Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
Med Biol Eng Comput. 2011 Aug;49(8):957-66. doi: 10.1007/s11517-011-0789-0. Epub 2011 Jun 28.
In this article, we propose a method for automated tracking and analysis of vesicle contours in video sequences acquired by phase contrast microscopy. The contour is determined in each frame of the selected video sequence by detecting the transition between the interior and exterior of the vesicle that is reflected in the image intensity gradients. The resulting contour points are represented in the polar coordinate system, i.e., with uniform angular sampling and with coordinates that originate from the vesicle center of mass, enabling the analysis of the vesicle shape and its membrane fluctuations. By analyzing artificial images with known ground-truth contours, the accuracy and precision of the proposed method was estimated to be 34.1 and 26.9 nm for image signal-to-noise ratio of 23 dB and pixel size of 35 nm, respectively. The proposed method was evaluated on quasi-spherical vesicles made up of different proportions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol and exposed to different temperatures. The results show that the method is robust and efficient in terms of speed and quantitative description of vesicle fluctuations. The magnitude of vesicle membrane fluctuations increased with temperature, while the bending rigidity of the membrane was increasing for temperatures up to 20 °C and decreasing for higher temperatures irrespective of the vesicle molecular structure.
在本文中，我们提出了一种用于通过相差显微镜获取的视频序列中囊泡轮廓自动跟踪和分析的方法。通过检测囊泡内部和外部之间的过渡来确定所选视频序列的每一帧中的轮廓，该过渡反映在图像强度梯度中。得到的轮廓点在极坐标系统中表示，即具有均匀的角采样并且坐标以囊泡质心为原点，从而能够分析囊泡的形状及其膜波动。通过分析具有已知真实轮廓的人工图像，我们估计对于信噪比为 23 dB 和像素尺寸为 35 nm 的图像，所提出方法的准确性和精度分别为 34.1nm 和 26.9nm。该方法在由不同比例的 1-棕榈酰基-2-油酰基-sn-甘油-3-磷酸胆碱（POPC）和胆固醇组成的准球形囊泡上进行了评估，并暴露于不同的温度下。结果表明，该方法在速度和囊泡波动的定量描述方面具有鲁棒性和高效性。囊泡膜波动的幅度随温度升高而增加，而膜的弯曲刚度在温度达到 20°C 之前增加，在更高温度下则降低，而与囊泡的分子结构无关。
