title: Apparent Diffusion Coefficient (ADC) as a quantitative parameter in diffusion weighted MR imaging in gynecologic cancer: Dependence on b-values used.
abstract: BACKGROUND
  Diffusion weighted imaging (DWI) has gained interest as an imaging modality for assessment of tumor extension and response to cancer treatment. The purpose of this study is to assess the impact of the choice of b-values on the calculation of the Apparent Diffusion Coefficient (ADC) for locally advanced gynecological cancer and to estimate a stable interval of diffusion gradients that allows for best comparison of the ADC between patients and institutions.
  
  
  METHODS
  Six patients underwent a high resolution single shot EPI based DWI scan with 16 different diffusion gradients on a 3 Tesla Philips Achieva MR-scanner. Data analysis was performed by applying a monoexponential and a biexponential model to the acquired data. The biexponential function models the effect of both perfusion and diffusion.
  
  
  CONCLUSIONS
  ADC changes of up to 40% were seen with the use of different b-values. Using a lower b-value ≥ 150 s/mm(2) and an upper b-value ≥ 700 s/mm(2) limited the variation to less that 10% from the reference ADC value. By eliminating the contribution of perfusion the uncertainty of quantitative ADC values were significantly reduced.
authors.affiliation: Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. jespkall@rm.dk
authors.forename: Jesper Folsted
authors.initials: JF
authors.lastname: Kallehauge
authors.forename: Kari
authors.initials: K
authors.lastname: Tanderup
authors.forename: Søren
authors.initials: S
authors.lastname: Haack
authors.forename: Thomas
authors.initials: T
authors.lastname: Nielsen
authors.forename: Ludvig Paul
authors.initials: LP
authors.lastname: Muren
authors.forename: Lars
authors.initials: L
authors.lastname: Fokdal
authors.forename: Jacob Christian
authors.initials: JC
authors.lastname: Lindegaard
authors.forename: Erik Morre
authors.initials: EM
authors.lastname: Pedersen
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D005260:Female; D005833:Genital Neoplasms, Female / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D005836:Genitalia, Female / Q000098:blood supply / Q000000981:diagnostic imaging; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods / Q000592:standards; D008962:Models, Theoretical; D011859:Radiography; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D013223:Statistics as Topic; D047368:Tumor Burden