RMIT University, Victoria 3001, Australia.
IEEE Trans Med Imaging. 2011 Feb;30(2):243-50. doi: 10.1109/TMI.2010.2076322. Epub 2010 Sep 16.
We have developed a robust method to perform retinal vascular fractal analysis from digital retina images. The technique preprocesses the green channel retina images with Gabor wavelet transforms to enhance the retinal images. Fourier Fractal dimension is computed on these preprocessed images and does not require any segmentation of the vessels. This novel technique requires human input only at a single step; the allocation of the optic disk center. We have tested this technique on 380 retina images from healthy individuals aged 50+ years, randomly selected from the Blue Mountains Eye Study population. To assess its reliability in assessing retinal vascular fractals from different allocation of optic center, we performed pair-wise Pearson correlation between the fractal dimension estimates with 100 simulated region of interest for each of the 380 images. There was Gaussian distribution variation in the optic center allocation in each simulation. The resulting mean correlation coefficient (standard deviation) was 0.93 (0.005). The repeatability of this method was found to be better than the earlier box-counting method. Using this method to assess retinal vascular fractals, we have also confirmed a reduction in the retinal vasculature complexity with aging, consistent with observations from other human organ systems.
我们已经开发出一种强大的方法，可从数字视网膜图像中进行视网膜血管分形分析。该技术使用 Gabor 小波变换预处理绿色通道视网膜图像，以增强视网膜图像。在这些预处理图像上计算傅立叶分形维数，并且不需要对血管进行任何分割。这种新技术仅需要在单个步骤中输入人工信息；分配视盘中心。我们已经在来自年龄在 50 岁以上的健康个体的 380 张视网膜图像上测试了该技术，这些图像是从蓝山眼研究人群中随机选择的。为了评估该技术在评估不同视盘中心分配的视网膜血管分形方面的可靠性，我们对每张图像的 380 个模拟感兴趣区域中的 100 个进行了分形维数估计的成对 Pearson 相关性分析。在每次模拟中，视盘中心的分配都存在高斯分布变化。结果的平均相关系数（标准偏差）为 0.93（0.005）。该方法的可重复性被发现优于早期的盒子计数法。使用这种方法评估视网膜血管分形，我们还证实了随着年龄的增长，视网膜血管复杂性的降低，这与其他人类器官系统的观察结果一致。
