title: Volumetry of the dominant intraprostatic tumour lesion: intersequence and interobserver differences on multiparametric MRI.
abstract: OBJECTIVE
  To establish the interobserver reproducibility of tumour volumetry on individual multiparametric (mp) prostate MRI sequences, validate measurements with histology and determine whether functional to morphological volume ratios reflect Gleason score.
  
  
  METHODS
  41 males with prostate cancer treated with prostatectomy (Cohort 1) or radical radiotherapy (Cohort 2), who had pre-treatment mpMRI [T2weighted (T2W) MRI, diffusion-weighted (DW)-MRI and dynamic contrast-enhanced (DCE)-MRI], were studied retrospectively. Dominant intraprostatic lesions (DIPLs) were manually delineated on each sequence and volumes were compared between observers (n = 40 analyzable) and with radical prostatectomy (n = 20). Volume ratios of DW-MRI and DCE-MRI to T2W MRI were documented and compared between Gleason grade 3 + 3, 3 + 4 and 4 + 3 or greater categories.
  
  
  RESULTS
  Limits of agreement of DIPL volumes between observers were: T2W MRI 0.9, -1.1 cm3, DW-MRI 1.3, -1.7 cm3and DCE-MRI 0.74, -0.89 cm3. In Cohort 1, T2W volumes overestimated fixed specimen histological volumes (+33% Observer 1, +16% Observer 2); DW- and DCE-MRI underestimated histological volume, the latter markedly so (-32% Observer 1, -79% Observer 2). Differences between T2W, DW- and DCE-MRI volumes were significant (p < 10-8). The ratio of DW-MRI volume (73.9 ± 18.1% Observer 1, 72.5 ± 21.9% Observer 2) and DCE-MRI volume (42.6 ± 24.6% Observer 1, 34.3 ± 24.9% Observer 2) to T2W volume was significantly different (p < 10-8), but these volume ratios did not differ between the Gleason grades.
  
  
  CONCLUSIONS
  The low variability of the DIPL volume on T2W MRI between Observers and agreement with histology indicates its suitability for delineation of gross tumour volume for radiotherapy planning. The volume of cellular tumour represented by DW-MRI is greater than the vascular (DCE) abnormality; ratios of both to T2W volume are independent of Gleason score. Advances in knowledge: (1) Manual volume measurement of tumour is reproducible within 1 cm3between observers on all sequences, confirming suitability across observers for radiotherapy planning. (2) Volumes derived on T2W MRI most accurately represent in vivo lesion volumes. (3) The proportion of cellular (DW-MRI) or vascular (DCE-MRI) volume to morphological (T2W MRI) volume is not affected by Gleason score.
authors.affiliation: 1 Cancer Research UK Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Hugh
authors.initials: H
authors.lastname: Harvey
authors.affiliation: 1 Cancer Research UK Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Orton
authors.affiliation: 1 Cancer Research UK Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Veronica A
authors.initials: VA
authors.lastname: Morgan
authors.affiliation: 2 Academic Urology Unit, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Parker
authors.affiliation: 2 Academic Urology Unit, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Dearnaley
authors.affiliation: 3 Department of Histopathology, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Cyril
authors.initials: C
authors.lastname: Fisher
authors.affiliation: 1 Cancer Research UK Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Nandita M
authors.initials: NM
authors.lastname: deSouza
mesh_terms: D000368:Aged; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D060787:Neoplasm Grading; D015588:Observer Variation; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D047368:Tumor Burden
chemical_list: D003287:Contrast Media