title: Evaluation of diffusion models in breast cancer.
abstract: OBJECTIVE
  The purpose of this study is to investigate whether the microvascular pseudodiffusion effects resulting with non-monoexponential behavior are present in breast cancer, taking into account tumor spatial heterogeneity. Additionally, methodological factors affecting the signal in low and high diffusion-sensitizing gradient ranges were explored in phantom studies.
  
  
  METHODS
  The effect of eddy currents and accuracy of b-value determination using a multiple b-value diffusion-weighted MR imaging sequence were investigated in test objects. Diffusion model selection and noise were then investigated in volunteers (n = 5) and breast tumor patients (n = 21) using the Bayesian information criterion.
  
  
  RESULTS
  54.3% of lesion voxels were best fitted by a monoexponential, 26.2% by a stretched-exponential, and 19.5% by a biexponential intravoxel incoherent motion (IVIM) model. High correlation (0.92) was observed between diffusion coefficients calculated using mono- and stretched-exponential models and moderate (0.59) between monoexponential and IVIM (medians: 0.96/0.84/0.72 × 10(-3) mm(2)/s, respectively). Distortion due to eddy currents depended on the direction of the diffusion gradient and displacement varied between 1 and 6 mm for high b-value images. Shift in the apparent diffusion coefficient due to intrinsic field gradients was compensated for by averaging diffusion data obtained from opposite directions.
  
  
  CONCLUSIONS
  Pseudodiffusion and intravoxel heterogeneity effects were not observed in approximately half of breast cancer and normal tissue voxels. This result indicates that stretched and IVIM models should be utilized in regional analysis rather than global tumor assessment. Cross terms between diffusion-sensitization gradients and other imaging or susceptibility-related gradients are relevant in clinical protocols, supporting the use of geometric averaging of diffusion-weighted images acquired with diffusion-sensitization gradients in opposite directions.
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Rafal
authors.initials: R
authors.lastname: Panek
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Borri
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Orton
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: O'Flynn
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Veronica
authors.initials: V
authors.lastname: Morgan
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Giles
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Nandita
authors.initials: N
authors.lastname: deSouza
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Martin O
authors.initials: MO
authors.lastname: Leach
authors.affiliation: Cancer Research UK Cancer Imaging Centre, Division of Radiotherapy and Imaging, The Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Schmidt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001499:Bayes Theorem; D001940:Breast / Q000033:anatomy & histology / Q000473:pathology* / Q000502:physiology / Q000503:physiopathology; D001943:Breast Neoplasms / Q000473:pathology* / Q000503:physiopathology; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008875:Middle Aged; D008962:Models, Theoretical; D019047:Phantoms, Imaging