title: Mediastinal lymph node detection and station mapping on chest CT using spatial priors and random forest.
abstract: OBJECTIVE
  To develop an automated system for mediastinal lymph node detection and station mapping for chest CT.
  
  
  METHODS
  The contextual organs, trachea, lungs, and spine are first automatically identified to locate the region of interest (ROI) (mediastinum). The authors employ shape features derived from Hessian analysis, local object scale, and circular transformation that are computed per voxel in the ROI. Eight more anatomical structures are simultaneously segmented by multiatlas label fusion. Spatial priors are defined as the relative multidimensional distance vectors corresponding to each structure. Intensity, shape, and spatial prior features are integrated and parsed by a random forest classifier for lymph node detection. The detected candidates are then segmented by the following curve evolution process. Texture features are computed on the segmented lymph nodes and a support vector machine committee is used for final classification. For lymph node station labeling, based on the segmentation results of the above anatomical structures, the textual definitions of mediastinal lymph node map according to the International Association for the Study of Lung Cancer are converted into patient-specific color-coded CT image, where the lymph node station can be automatically assigned for each detected node.
  
  
  RESULTS
  The chest CT volumes from 70 patients with 316 enlarged mediastinal lymph nodes are used for validation. For lymph node detection, their system achieves 88% sensitivity at eight false positives per patient. For lymph node station labeling, 84.5% of lymph nodes are correctly assigned to their stations.
  
  
  CONCLUSIONS
  Multiple-channel shape, intensity, and spatial prior features aggregated by a random forest classifier improve mediastinal lymph node detection on chest CT. Using the location information of segmented anatomic structures from the multiatlas formulation enables accurate identification of lymph node stations.
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Jiamin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Joanne
authors.initials: J
authors.lastname: Hoffman
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Yao
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Le
authors.initials: L
authors.lastname: Lu
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Lauren
authors.initials: L
authors.lastname: Kim
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Evrim B
authors.initials: EB
authors.lastname: Turkbey
authors.affiliation: Imaging Biomarkers and Computer-aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center Building, 10 Room 1C224 MSC 1182, Bethesda, Maryland 20892-1182.
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Summers
mesh_terms: D001271:Atlases as Topic; D005189:False Positive Reactions; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging*; D008482:Mediastinum / Q000000981:diagnostic imaging*; D013902:Radiography, Thoracic / Q000379:methods*; D012680:Sensitivity and Specificity; D060388:Support Vector Machine; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*