title: A robust statistics driven volume-scalable active contour for segmenting anatomical structures in volumetric medical images with complex conditions.
abstract: BACKGROUND
  Accurate segmentation of anatomical structures in medical images is a critical step in the development of computer assisted intervention systems. However, complex image conditions, such as intensity inhomogeneity, noise and weak object boundary, often cause considerable difficulties in medical image segmentation. To cope with these difficulties, we propose a novel robust statistics driven volume-scalable active contour framework, to extract desired object boundary from magnetic resonance (MR) and computed tomography (CT) imagery in 3D.
  
  
  METHODS
  We define an energy functional in terms of the initial seeded labels and two fitting functions that are derived from object local robust statistics features. This energy is then incorporated into a level set scheme which drives the active contour evolving and converging at the desired position of the object boundary. Due to the local robust statistics and the volume scaling function in the energy fitting term, the object features in local volumes are learned adaptively to guide the motion of the contours, which thereby guarantees the capability of our method to cope with intensity inhomogeneity, noise and weak boundary. In addition, the initialization of active contour is simplified by select several seeds in the object and/or background to eliminate the sensitivity to initialization.
  
  
  RESULTS
  The proposed method was applied to extensive public available volumetric medical images with challenging image conditions. The segmentation results of various anatomical structures, such as white matter (WM), atrium, caudate nucleus and brain tumor, were evaluated quantitatively by comparing with the corresponding ground truths. It was found that the proposed method achieves consistent and coherent segmentation accuracy of 0.9246 ± 0.0068 for WM, 0.9043 ± 0.0131 for liver tumors, 0.8725 ± 0.0374 for caudate nucleus, 0.8802 ± 0.0595 for brain tumors, etc., measured by Dice similarity coefficients value for the overlap between the algorithm one and the ground truth. Further comparative experimental results showed desirable performances of the proposed method over several well-known segmentation methods in terms of accuracy and robustness.
  
  
  CONCLUSIONS
  We proposed an approach to accurate segment volumetric medical images with complex conditions. The accuracy of segmentation, robustness to noise and contour initialization were validated on the basis of extensive MR and CT volumes.
authors.affiliation: School of Computer Science and Technology, Biocomputing Research Center, Harbin Institute of Technology, Harbin, China. wangkq@hit.edu.cn.
authors.forename: Kuanquan
authors.initials: K
authors.lastname: Wang
authors.affiliation: School of Computer Science and Technology, Biocomputing Research Center, Harbin Institute of Technology, Harbin, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Ma
mesh_terms: D000715:Anatomy; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D000069550:Machine Learning; D008279:Magnetic Resonance Imaging; D015233:Models, Statistical; D013223:Statistics as Topic / Q000379:methods*; D014057:Tomography, X-Ray Computed
keywords: Active contour; Complex conditions; Robust statistics; Volume scalable; Volumetric medical image segmentation