title: 3 Tesla multiparametric MRI for GTV-definition of Dominant Intraprostatic Lesions in patients with Prostate Cancer--an interobserver variability study.
abstract: OBJECTIVE
  To evaluate the interobserver variability of gross tumor volume (GTV) - delineation of Dominant Intraprostatic Lesions (DIPL) in patients with prostate cancer using published MRI criteria for multiparametric MRI at 3 Tesla by 6 different observers.
  
  
  METHODS
  90 GTV-datasets based on 15 multiparametric MRI sequences (T2w, diffusion weighted (DWI) and dynamic contrast enhanced (DCE)) of 5 patients with prostate cancer were generated for GTV-delineation of DIPL by 6 observers. The reference GTV-dataset was contoured by a radiologist with expertise in diagnostic imaging of prostate cancer using MRI. Subsequent GTV-delineation was performed by 5 radiation oncologists who received teaching of MRI-features of primary prostate cancer before starting contouring session. GTV-datasets were contoured using Oncentra Masterplan® and iplan® Net. For purposes of comparison GTV-datasets were imported to the Artiview® platform (Aquilab®), GTV-values and the similarity indices or Kappa indices (KI) were calculated with the postulation that a KI > 0.7 indicates excellent, a KI > 0.6 to < 0.7 substantial and KI > 0.5 to < 0.6 moderate agreement. Additionally all observers rated difficulties of contouring for each MRI-sequence using a 3 point rating scale (1 = easy to delineate, 2 = minor difficulties, 3 = major difficulties).
  
  
  RESULTS
  GTV contouring using T2w (KI-T2w = 0.61) and DCE images (KI-DCE = 0.63) resulted in substantial agreement. GTV contouring using DWI images resulted in moderate agreement (KI-DWI = 0.51). KI-T2w and KI-DCE was significantly higher than KI-DWI (p = 0.01 and p = 0.003). Degree of difficulty in contouring GTV was significantly lower using T2w and DCE compared to DWI-sequences (both p < 0.0001). Analysis of delineation differences revealed inadequate comparison of functional (DWI, DCE) to anatomical sequences (T2w) and lack of awareness of non-specific imaging findings as a source of erroneous delineation.
  
  
  CONCLUSIONS
  Using T2w and DCE sequences at 3 Tesla for GTV-definition of DIPL in prostate cancer patients by radiation oncologists with knowledge of MRI features results in substantial agreement compared to an experienced MRI-radiologist, but for radiotherapy purposes higher KI are desirable, strengthen the need for expert surveillance. DWI sequence for GTV delineation was considered as difficult in application.
authors.affiliation: Department of Radiation Oncology, University of Freiburg, Robert Koch Str. 3, 79106 Freiburg, Germany. hans.christian.rischke@uniklinik-freiburg.de
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Rischke
authors.forename: Ursula
authors.initials: U
authors.lastname: Nestle
authors.forename: Tobias
authors.initials: T
authors.lastname: Fechter
authors.forename: Christian
authors.initials: C
authors.lastname: Doll
authors.forename: Natalja
authors.initials: N
authors.lastname: Volegova-Neher
authors.forename: Karl
authors.initials: K
authors.lastname: Henne
authors.forename: Jutta
authors.initials: J
authors.lastname: Scholber
authors.forename: Stefan
authors.initials: S
authors.lastname: Knippen
authors.forename: Simon
authors.initials: S
authors.lastname: Kirste
authors.forename: Anca L
authors.initials: AL
authors.lastname: Grosu
authors.forename: Cordula A
authors.initials: CA
authors.lastname: Jilg
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000473:pathology*; D011880:Radiotherapy Planning, Computer-Assisted