A new algorithm for segmentation of suspected lung ROI(regions of interest)by mean-shift clustering and multi-scale HESSIAN matrix dot filtering was proposed.Original image was firstly filtered by multi-scale HESSIAN matrix dot filters,round suspected nodular lesions in the image were enhanced,and linear shape regions of the trachea and vascular were suppressed.Then,three types of information,such as,shape filtering value of HESSIAN matrix,gray value,and spatial location,were introduced to feature space.The kernel function of mean-shift clustering was divided into product form of three kinds of kernel functions corresponding to the three feature information.Finally,bandwidths were calculated adaptively to determine the bandwidth of each suspected area,and they were used in mean-shift clustering segmentation.Experimental results show that by the introduction of HESSIAN matrix of dot filtering information to mean-shift clustering,nodular regions can be segmented from blood vessels,trachea,or cross regions connected to the nodule,non-nodular areas can be removed from ROIs properly,and ground glass object(GGO)nodular areas can also be segmented.For the experimental data set of 127 different forms of nodules,the average accuracy of the proposed algorithm is more than 90%.
针对传统方法通常选取角点或极值点作为特征点,忽略了局部纹理变化从而影响医学影像分类性能的问题,提出一种新的特征点检测和描述方法,并应用Bag-of-Keypoints模型实现医学影像分类。首先改进自适应的Kmeans对影像进行像素级聚类,构建核值相似区并选取邻域内聚类分布变化急剧的像素点作为特征点;然后在极坐标系中定义特征点描述符并生成视觉词典,通过视觉词直方图描述影像;最后利用直方图交集方法度量影像间的相似度来扩展KNN(K-nearest neighbor)完成分类。遵循IRMA(image retrival in medical appication)的医学影像类别编码标准,严格选择实验数据,结果表明该算法较传统方法 F1值平均提高4.5%,对于不同类别影像效果更加稳定鲁棒,从而更好地满足临床应用需求。
