title: Contour propagation using non-uniform cubic B-splines for lung tumor delineation in 4D-CT.
abstract: OBJECTIVE
  Accurate target delineation is a critical step in radiotherapy. In this study, a robust contour propagation method is proposed to help physicians delineate lung tumors in four-dimensional computer tomography (4D-CT) images efficiently and accurately.
  
  
  METHODS
  The proposed method starts with manually delineated contours on the reference phase. Each contour is fitted by a non-uniform cubic B-spline curve, and its deformation on the target phase is achieved by moving its control vertexes such that the intensity similarity between the two contours is maximized. Since contour is usually the boundary of lesion or tissue which may deform quite differently from the tissues outside the boundary, the proposed method treats each contour as a deformable entity, a non-uniform cubic B-spline curve, and focuses on the registration of contour entity instead of the entire image to avoid the deformation of contour to be smoothed by its surrounding tissues, meanwhile to greatly reduce the time consumption while keeping the accuracy of the contour propagation. Eighteen 4D-CT cases with 444 gross tumor volume (GTV) contours manually delineated slice by slice on the maximal inhale and exhale phases are used to verify the proposed method.
  
  
  RESULTS
  The Jaccard similarity coefficient (JSC) between the propagated GTV and the manually delineated GTV is 0.885 ± 0.026, and the Hausdorff distance (HD) is [Formula: see text] mm. In addition, the time for propagating GTV to all the phases is 3.67 ± 3.41 minutes. The results are better than fast adaptive stochastic gradient descent (FASGD) B-spline method, 3D+t B-spline method and diffeomorphic Demons method.
  
  
  CONCLUSIONS
  The proposed method is useful to help physicians delineate target volumes efficiently and accurately.
authors.affiliation: Center for Biomedical Imaging and Bioinformatics, School of Computer Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|The Key Laboratory of Image Processing and Intelligent Control, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Yongchuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Center for Biomedical Imaging and Bioinformatics, School of Computer Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China. jrc@hust.edu.cn.|The Key Laboratory of Image Processing and Intelligent Control, Ministry of Education, Wuhan, Hubei, China. jrc@hust.edu.cn.
authors.forename: Renchao
authors.identifier: http://orcid.org/0000-0002-1591-3510
authors.initials: R
authors.lastname: Jin
authors.affiliation: Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Mi
authors.initials: M
authors.lastname: Chen
authors.affiliation: Center for Biomedical Imaging and Bioinformatics, School of Computer Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|The Key Laboratory of Image Processing and Intelligent Control, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Enmin
authors.initials: E
authors.lastname: Song
authors.affiliation: Center for Biomedical Imaging and Bioinformatics, School of Computer Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|The Key Laboratory of Image Processing and Intelligent Control, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Xu
authors.affiliation: Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Sino-US Intelligent Information Processing Joint Lab, Anyang Normal University, Anyang, Henan, China.|Center for Machine Vision and Security Research, Kennesaw State University, Marietta Campus, Kennesaw, GA, USA.
authors.forename: Chih-Cheng
authors.initials: CC
authors.lastname: Hung
mesh_terms: D000465:Algorithms; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
keywords: Contour propagation; Deformable image registration; Lung cancer; Radiation therapy; Target volume delineation