Santarelli M F, Positano V, Michelassi C, Lombardi M, Landini L
C.N.R. Institute of Clinical Physiology, Via Moruzzi, 1, Loc. S. Cataldo, 56124 Pisa, Italy.
Med Eng Phys. 2003 Mar;25(2):149-59. doi: 10.1016/s1350-4533(02)00144-3.
We present a new approach to magnetic resonance image segmentation with a Gradient-Vector-Flow-based snake applied to selective smoothing filtered images. The system also allows automated image segmentation in the presence of grey scale inhomogeneity, as in cardiac Magnetic Resonance imaging. Removal of such inhomogeneities is a difficult task, but we proved that using non-linear anisotropic diffusion filtering, myocardium edges are selectively preserved. The approach allowed medical data to be automatically segmented in order to track not only endocardium, which is usually a less difficult task, but also epicardium in anatomic and perfusion studies with Magnetic Resonance. The method developed proceeds in three distinct phases: (a) an anisotropic diffusion filtering tool is used to reduce grey scale inhomogeneity and to selectively preserve edges; (b) a Gradient-Vector-Flow-based snake is applied on filtered images to allow capturing a snake from a long range and to move into concave boundary regions; and (c) an automatic procedure based on a snake is used to fit both endocardium and epicardium borders in a multiphase, multislice examination. A good agreement (P<0.001) between manual and automatic data analysis, based on the mean difference+/-SD, was assessed in a pool of 907 cardiac function and perfusion images.
我们提出了一种新的磁共振图像分割方法，该方法将基于梯度向量流的蛇形模型应用于选择性平滑滤波后的图像。该系统还允许在存在灰度不均匀性的情况下进行自动图像分割，例如在心脏磁共振成像中。去除这种不均匀性是一项艰巨的任务，但我们证明使用非线性各向异性扩散滤波，可以选择性地保留心肌边缘。该方法允许对医学数据进行自动分割，以便不仅可以追踪通常较容易的内膜，还可以在磁共振的解剖学和灌注研究中追踪外膜。所开发的方法分三个不同阶段进行：(a) 使用各向异性扩散滤波工具来减少灰度不均匀性并选择性地保留边缘；(b) 将基于梯度向量流的蛇形模型应用于滤波后的图像，以允许从远距离捕获蛇形模型并移动到凹形边界区域；(c) 使用基于蛇形模型的自动程序在多阶段、多层检查中拟合内膜和外膜边界。在907幅心脏功能和灌注图像中，基于平均差值±标准差评估了手动和自动数据分析之间的良好一致性（P<0.001）。
