title: Modelling DW-MRI data from primary and metastatic ovarian tumours.
abstract: OBJECTIVE
  To assess goodness-of-fit and repeatability of mono-exponential, stretched exponential and bi-exponential models of diffusion-weighted MRI (DW-MRI) data in primary and metastatic ovarian cancer.
  
  
  METHODS
  Thirty-nine primary and metastatic lesions from thirty-one patients with stage III or IV ovarian cancer were examined before and after chemotherapy using DW-MRI with ten diffusion-weightings. The data were fitted with (a) a mono-exponential model to give the apparent diffusion coefficient (ADC), (b) a stretched exponential model to give the distributed diffusion coefficient (DDC) and stretching parameter (α), and (c) a bi-exponential model to give the diffusion coefficient (D), perfusion fraction (f) and pseudodiffusion coefficient (D*).
  
  
  RESULTS
  Coefficients of variation, established from repeated baseline measurements, were: ADC 3.1%, DDC 4.3%, α 7.0%, D 13.2%, f 44.0%, D* 165.1%. The bi-exponential model was unsuitable in these data owing to poor repeatability. After excluding the bi-exponential model, analysis using Akaike Information Criteria showed that the stretched exponential model provided the better fit to the majority of pixels in 64% of lesions.
  
  
  CONCLUSIONS
  The stretched exponential model provides the optimal fit to DW-MRI data from ovarian, omental and peritoneal lesions and lymph nodes in pre-treatment and post-treatment measurements with good repeatability.
  
  
  CONCLUSIONS
  • DW-MRI data in ovarian cancer show deviation from mono-exponential behaviour • Parameters derived from the stretched exponential model showed good repeatability (CV 7%) • The bi-exponential model was unsuitable because of poor parameter repeatability • The stretched exponential model showed comparable repeatability to the mono-exponential model • The extra parameter (α) provides scope for investigation of heterogeneity or response.
authors.affiliation: CRUK and EPSRC Cancer Imaging Centre, Division of Radiotherapy and Imaging, Institute of Cancer Research, 15 Cotswold Road, Sutton, Surrey, SM2 5NG, UK, jessica.winfield@icr.ac.uk.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Winfield
authors.forename: Nandita M
authors.initials: NM
authors.lastname: deSouza
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Priest
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Wakefield
authors.forename: Charlotte
authors.initials: C
authors.lastname: Hodgkin
authors.forename: Susan
authors.initials: S
authors.lastname: Freeman
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Orton
authors.forename: David J
authors.initials: DJ
authors.lastname: Collins
mesh_terms: D000077216:Carcinoma, Ovarian Epithelial; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000556:secondary; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008954:Models, Biological; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000473:pathology*; D009375:Neoplasms, Glandular and Epithelial / Q000188:drug therapy / Q000473:pathology*; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000473:pathology*; D010534:Peritoneal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000556:secondary; D015203:Reproducibility of Results