title: Inter and intraobserver variation in gross tumor delineation on megavoltage CT images in patients undergoing tomotherapy-based image-guided radiotherapy for postoperative vault recurrences.
abstract: OBJECTIVE
  This study was designed to evaluate inter and intraobserver concordance in gross tumor volume (GTV) delineation on megavoltage CT (MVCT) images in patients with postoperative vault recurrences.
  
  
  METHODS
  Three observers delineated GTV on MVCT and CECT and two observers recontoured on MVCT images. Tumor volumes were calculated and correlated using Spearman correlation. The standard deviation of centre of mass was averaged on per patient basis. The ratio of common volume and encompassing volume was used to determine intra and interobserver spatial concordance. Lack of difference in spatial concordance ratio between MVCT and CECT images was used as an index of usability of MVCT images.
  
  
  RESULTS
  Thirty six datasets were available for seven patients. High intraobserver GTV correlation was recorded for observer 1 and 2 (r = 0.93 and r = 0.98; P=0.03 and 0.0001). The average intraobserver spatial concordance ratio was 0.57 and 0.62 respectively. The mean GTV of observers 1, 2 and 3 were 31.6 (18.7-52.2); 28.2 (16.7-51.8) and 46.3 cc (29.1-90.5) respectively. Average standard deviation of centre of mass of all observers was less than 5 mm in either direction. Largest interobserver discordance was observed in anterior, inferior and lateral direction. The interobserver spatial concordance of GTV on MVCT and CECT images was 0.34 and 0.36 (P=0.24) respectively.
  
  
  CONCLUSIONS
  Moderate to good inter and intraobserver GTV correlation was observed on MVCT images, however, was associated with low interobserver spatial concordance on both MVCT and CECT images. Strategies to improve contouring reproducibility on MVCT and KVCT images are desirable.
authors: Department of Radiation Oncology, Advanced Centre for Treatment, Education and Research in Cancer, Tata Memorial Centre, Mumbai, India.
authors: Mahesh
authors: M
authors: Upasani
authors: Supriya
authors: S
authors: Chopra
authors: Reena
authors: R
authors: Engineer
authors: Seema
authors: S
authors: Medhi
authors: Zubin
authors: Z
authors: Master
authors: Umesh
authors: U
authors: Mahantshetty
authors: Shyam Kishore
authors: SK
authors: Shrivastava
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D015588:Observer Variation; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden