title: Early postoperative MRI overestimates residual tumour after resection of gliomas with no or minimal enhancement.
abstract: BACKGROUND
  Standards for residual tumour measurement after resection of gliomas with no or minimal enhancement have not yet been established. In this study residual volumes on early and late postoperative T2-/FLAIR-weighted MRI are compared.
  
  
  METHODS
  A retrospective cohort included 58 consecutive glioma patients with no or minimal preoperative gadolinium enhancement. Inclusion criteria were first-time resection between 2007 and 2009 with a T2-/FLAIR-based target volume and availability of preoperative, early (<48 h) and late (1-7 months) postoperative MRI. The volumes of non-enhancing T2/FLAIR tissue and diffusion restriction areas were measured.
  
  
  RESULTS
  Residual tumour volumes were 22% smaller on late postoperative compared with early postoperative T2-weighted MRI and 49% smaller for FLAIR-weighted imaging. Postoperative restricted diffusion volume correlated with the difference between early and late postoperative FLAIR volumes and with the difference between T2 and FLAIR volumes on early postoperative MRI.
  
  
  CONCLUSIONS
  We observed a systematic and substantial overestimation of residual non-enhancing volume on MRI within 48 h of resection compared with months postoperatively, in particular for FLAIR imaging. Resection-induced ischaemia contributes to this overestimation, as may other operative effects. This indicates that early postoperative MRI is less reliable to determine the extent of non-enhancing residual glioma and restricted diffusion volumes are imperative.
authors.affiliation: Neurosurgical Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Sinan M K
authors.initials: SM
authors.lastname: Belhawi
authors.forename: Friso W A
authors.initials: FW
authors.lastname: Hoefnagels
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Baaijen
authors.forename: Esther Sanchez
authors.initials: ES
authors.lastname: Aliaga
authors.forename: Jaap C
authors.initials: JC
authors.lastname: Reijneveld
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Heimans
authors.forename: Frederik
authors.initials: F
authors.lastname: Barkhof
authors.forename: W Peter
authors.initials: WP
authors.lastname: Vandertop
authors.forename: Philip C De Witt
authors.initials: PC
authors.lastname: Hamer
mesh_terms: D000328:Adult; D001932:Brain Neoplasms / Q000473:pathology* / Q000601:surgery*; D003287:Contrast Media; D005260:Female; D005910:Glioma / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D011184:Postoperative Period; D012189:Retrospective Studies; D018709:Statistics, Nonparametric
chemical_list: D003287:Contrast Media