title: Dosimetric impact of interobserver variability in MRI-based delineation for cervical cancer brachytherapy.
abstract: OBJECTIVE
  To study the dosimetric impact of interobserver delineation variability (IODV) in MRI-based cervical cancer brachytherapy.
  
  
  METHODS
  MR images of six patients were distributed to 10 experienced observers worldwide. They were asked to delineate the target volumes and the organs at risk (OARs) for each patient. Two types of reference contours were created (Expert Consensus - EC and Simultaneous Truth and Performance Level Estimation - STAPLE). Optimised plans based on both EC- and STAPLE-contours were prepared. These plans were transferred to each of the observer contour sets and the resulting DVH parameters (D(90) and D(2cc)) were calculated. For each patient the standard deviation (SD) for the 10 observers was calculated.
  
  
  RESULTS
  A mean relative SD of 8-10% was found for GTV and High Risk CTV (HR-CTV) D(90) analysing one single fraction. For rectum and bladder the mean relative SD for D(2cc) was 5-8% while sigmoid was at 11%. For the whole treatment the IODV in HR-CTV caused an uncertainty of ±5 Gy(α/β=10) (1SD). The corresponding figure for OARs was ±2-3 Gy(α/β=3). The results were not sensitive as to which structure set was used for the optimisation.
  
  
  CONCLUSIONS
  For the target volumes the dosimetric impact of IODV was smallest for the GTV and HR-CTV, while IODV had an even smaller impact on the bladder and rectum.
authors: Department of Medical Physics, Oslo University Hospital, The Radium Hospital, Oslo, Norway. taran.paulsen.hellebust@nrpa.no
authors: Taran Paulsen
authors: TP
authors: Hellebust
authors: Kari
authors: K
authors: Tanderup
authors: Christoffer
authors: C
authors: Lervåg
authors: Elena
authors: E
authors: Fidarova
authors: Daniel
authors: D
authors: Berger
authors: Eirik
authors: E
authors: Malinen
authors: Richard
authors: R
authors: Pötter
authors: Primož
authors: P
authors: Petrič
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D015588:Observer Variation; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D047368:Tumor Burden; D035501:Uncertainty; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*