title: Susceptibility changes in meningiomas influence the apparent diffusion coefficient in diffusion-weighted MRI.
abstract: BACKGROUND
  Cell-dense tumors may restrict diffusivity which can be measured by diffusion-weighted MRI (DWI), and which is quantified by the apparent diffusion coefficient (ADC). Little is known about diffusivity in meningiomas. These tumors frequently show hemorrhage and calcification which can be demonstrated using susceptibility weighted MRI (SWI). Both DWI and SWI represent T2-derived MRI sequences. Here we investigated ADC variability in meningiomas and analyzed whether susceptibility changes (SWIpos) alter diffusivity.
  
  
  METHODS
  We grouped newly diagnosed meningiomas according to the presence (SWIpos) or absence (SWIneg) of susceptibility changes. ADC values were calculated using region-of-interest analysis, and ADC values of SWIpos and SWIneg meningiomas were compared. In addition ADC histograms were created.
  
  
  RESULTS
  We retrospectively studied 36 patients (13 WHO grade I, 8 WHO grade II, 15 suspected meningiomas). Thirteen meningiomas (36%) exhibited SWIpos. Global ADC values were higher in SWIpos (1.00 ± 0.15 × 10-3mm(2)/s) compared to SWIneg (0.82 ± 0.09 × 10-3mm(2)/s) tumors (P<0.0001). Meningiomas showing both SWIpos and SWIneg areas caused two separated histogram peaks, whereas homogeneously appearing meningiomas with either SWIposor SWIneg areas showed one peak only. ADC values did not correlate with age or gender, and showed substantial overlap between WHO grade I and II.
  
  
  CONCLUSIONS
  Susceptibility changes (SWIpos) in meningiomas influence measures of diffusivity by increasing ADC values on average by 38%. This shift has to be considered when conclusions on tumor behavior are drawn from DWI. Further studies should address whether ADC changes and histogram patterns can be used to monitor treatment of meningiomas.
authors.affiliation: Department of Neurosurgery/Brain Tumor Center, Cantonal Hospital Aarau, Tellstrasse, 5001 Aarau, Switzerland. Electronic address: lucia.schwyzer@ksa.ch.
authors.forename: L
authors.initials: L
authors.lastname: Schwyzer
authors.affiliation: Department of Neuroradiology, Cantonal Hospital, Aarau, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Berberat
authors.affiliation: Department of Neuroradiology, Cantonal Hospital, Aarau, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Remonda
authors.affiliation: Department of Neurology/Brain Tumor Center, Cantonal Hospital, Aarau, Switzerland.
authors.forename: U
authors.initials: U
authors.lastname: Roelcke
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging*; D008579:Meningioma / Q000000981:diagnostic imaging*; D008875:Middle Aged; D012189:Retrospective Studies
keywords: Apparent diffusion coefficient; Diffusion MRI; Meningioma; Susceptibility changes