title: Histological image segmentation using fast mean shift clustering method.
abstract: BACKGROUND
  Colour image segmentation is fundamental and critical for quantitative histological image analysis. The complexity of the microstructure and the approach to make histological images results in variable staining and illumination variations. And ultra-high resolution of histological images makes it is hard for image segmentation methods to achieve high-quality segmentation results and low computation cost at the same time.
  
  
  METHODS
  Mean Shift clustering approach is employed for histological image segmentation. Colour histological image is transformed from RGB to CIE L*a*b* colour space, and then a* and b* components are extracted as features. To speed up Mean Shift algorithm, the probability density distribution is estimated in feature space in advance and then the Mean Shift scheme is used to separate the feature space into different regions by finding the density peaks quickly. And an integral scheme is employed to reduce the computation cost of mean shift vector significantly. Finally image pixels are classified into clusters according to which region their features fall into in feature space.
  
  
  RESULTS
  Numerical experiments are carried on liver fibrosis histological images. Experimental results demonstrate that Mean Shift clustering achieves more accurate results than k-means but is computational expensive, and the speed of the improved Mean Shift method is comparable to that of k-means while the accuracy of segmentation results is the same as that achieved using standard Mean Shift method.
  
  
  CONCLUSIONS
  An effective and reliable histological image segmentation approach is proposed in this paper. It employs improved Mean Shift clustering, which is speed up by using probability density distribution estimation and the integral scheme.
authors.affiliation: School of Biomedical Engineering, Capital Medical University, Beijing, China. gemingwu@ccmu.edu.cn.
authors.forename: Geming
authors.initials: G
authors.lastname: Wu
authors.affiliation: Liver Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China. zhao_xinyan@ccmu.edu.cn.
authors.forename: Xinyan
authors.initials: X
authors.lastname: Zhao
authors.affiliation: School of Biomedical Engineering, Capital Medical University, Beijing, China. 15611828928@163.com.
authors.forename: Shuqian
authors.initials: S
authors.lastname: Luo
authors.affiliation: School of Biomedical Engineering, Capital Medical University, Beijing, China. shl@ccmu.edu.cn.
authors.forename: Hongli
authors.initials: H
authors.lastname: Shi
mesh_terms: D000465:Algorithms; D000818:Animals; D016000:Cluster Analysis; D003116:Color; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000648:ultrastructure; D008103:Liver Cirrhosis / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013194:Staining and Labeling; D013997:Time Factors