title: Interactive contour delineation of organs at risk in radiotherapy: Clinical evaluation on NSCLC patients.
abstract: OBJECTIVE
  Accurate delineation of organs at risk (OARs) on computed tomography (CT) image is required for radiation treatment planning (RTP). Manual delineation of OARs being time consuming and prone to high interobserver variability, many (semi-) automatic methods have been proposed. However, most of them are specific to a particular OAR. Here, an interactive computer-assisted system able to segment various OARs required for thoracic radiation therapy is introduced.
  
  
  METHODS
  Segmentation information (foreground and background seeds) is interactively added by the user in any of the three main orthogonal views of the CT volume and is subsequently propagated within the whole volume. The proposed method is based on the combination of watershed transformation and graph-cuts algorithm, which is used as a powerful optimization technique to minimize the energy function. The OARs considered for thoracic radiation therapy are the lungs, spinal cord, trachea, proximal bronchus tree, heart, and esophagus. The method was evaluated on multivendor CT datasets of 30 patients. Two radiation oncologists participated in the study and manual delineations from the original RTP were used as ground truth for evaluation.
  
  
  RESULTS
  Delineation of the OARs obtained with the minimally interactive approach was approved to be usable for RTP in nearly 90% of the cases, excluding the esophagus, which segmentation was mostly rejected, thus leading to a gain of time ranging from 50% to 80% in RTP. Considering exclusively accepted cases, overall OARs, a Dice similarity coefficient higher than 0.7 and a Hausdorff distance below 10 mm with respect to the ground truth were achieved. In addition, the interobserver analysis did not highlight any statistically significant difference, at the exception of the segmentation of the heart, in terms of Hausdorff distance and volume difference.
  
  
  CONCLUSIONS
  An interactive, accurate, fast, and easy-to-use computer-assisted system able to segment various OARs required for thoracic radiation therapy has been presented and clinically evaluated. The introduction of the proposed system in clinical routine may offer valuable new option to radiation oncologists in performing RTP.
authors.affiliation: AQUILAB, Loos-les-Lille 59120, France and University Lille, Inserm, CHU Lille, U1189-ONCO-THAI-Image Assisted Laser Therapy for Oncology, Lille F-59000, France.
authors.forename: J
authors.initials: J
authors.lastname: Dolz
authors.affiliation: AQUILAB, Loos-les-Lille 59120, France.
authors.forename: H A
authors.initials: HA
authors.lastname: Kirişli
authors.affiliation: Department of Radiation Oncology, University Medical Center, Freiburg 79106, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Fechter
authors.affiliation: Department of Radiation Oncology, University Medical Center, Freiburg 79106, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Karnitzki
authors.affiliation: Department of Radiation Oncology, University Medical Center, Freiburg 79106, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Oehlke
authors.affiliation: Department of Radiation Oncology, University Medical Center, Freiburg 79106, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Nestle
authors.affiliation: Inserm Onco Thai U1189, Université Lille 2, CHRU Lille, Lille 59037, France.
authors.forename: M
authors.initials: M
authors.lastname: Vermandel
authors.affiliation: AQUILAB, Loos-les-Lille 59120, France.
authors.forename: L
authors.initials: L
authors.lastname: Massoptier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D013909:Thorax / Q000000981:diagnostic imaging / Q000528:radiation effects; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*