title: Time window for postoperative reactive enhancement after resection of brain tumors: less than 72 hours.
abstract: OBJECTIVE
  Early postoperative MRI within 72 hours after brain tumor surgery is commonly used to assess residual contrast-enhancing tumor. The 72-hour window is commonly accepted because previous 1.5-T MRI studies have not found confounding postoperative reactive contrast enhancement in this time frame. The sensitivity to detect contrast enhancement increases with the field strengths. Therefore, the authors aimed to assess whether the 72-hour window is also appropriate for the MRI scanner with a field strength of 3 T.
  
  
  METHODS
  The authors retrospectively analyzed findings on early postsurgical MR images acquired in 46 patients treated for high-grade gliomas. They performed 3-T MRI within 7 days before surgery and within 72 hours thereafter. The appearance of enhancement was categorized as postoperative reactive enhancement or tumoral enhancement by comparison with the pattern and location of presurgical enhancing tumor.
  
  
  RESULTS
  Postoperative reactive enhancement was present in 15 patients (32.6%). This enhancement, not seen on presurgical MRI, had a marginal or leptomeningeal/dural pattern. In 13 patients (28.3%) postsurgical enhancement was found within the first 72 postoperative hours, with the earliest seen 22:57 hours after surgery. Subsequent MR scans in patients with postoperative reactive enhancement did not reveal tumor recurrence in these regions.
  
  
  CONCLUSIONS
  Postoperative reactive enhancement earlier than 72 hours after brain tumor surgery can be expected in about one-third of the cases in which a 3-T scanner is used. This might be due to the higher enhancement-to-brain contrast at higher field strengths. Therefore, the time window of 72 hours does not prevent reactive enhancement, which, however, can be recognized as such comparing it with presurgical enhancing tumor.
authors.affiliation: Institute of Neuroradiology and.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Lescher
authors.forename: Sonja
authors.initials: S
authors.lastname: Schniewindt
authors.forename: Alina
authors.initials: A
authors.lastname: Jurcoane
authors.forename: Christian
authors.initials: C
authors.lastname: Senft
authors.forename: Elke
authors.initials: E
authors.lastname: Hattingen
mesh_terms: D001932:Brain Neoplasms / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000517:prevention & control; D011183:Postoperative Complications / Q000175:diagnosis*; D012189:Retrospective Studies; D013997:Time Factors
keywords: MRI; brain tumors; iMRI = intraoperative MRI; postoperative enhancement; surgery; time window