title: Prospective study of postoperative magnetic resonance imaging in patients with malignant gliomas.
abstract: OBJECTIVE
  We studied the natural history of postoperative enhancement on magnetic resonance (MR) scans in patients with malignant glioma to determine the following: (1) when a postoperative MR scan most accurately shows residual enhancing tumor; and (2) whether repeated doses of the contrast agent gadopentetate dimeglumine (Gd-DTPA) were well tolerated.
  
  
  METHODS
  Seventeen patients with malignant glioma underwent tumor resection; four (24%) had nonenhancing tumors preoperatively. Serial MR scans were performed on postoperative days 1, 3, 5, 7, 14, and 21 and were analyzed qualitatively and quantitatively. The evolution of enhancement and subacute hemorrhage were described and measured. A uniform schedule of postoperative dexamethasone administration was used in all but four patients (24%) (each required higher doses to maintain neurologic function).
  
  
  RESULTS
  Nontumoral, marginal (i.e., postsurgical) enhancement, potentially mimicking residual tumor, developed in eight patients (53%), including tumors that were nonenhancing preoperatively, and was maximal from days 5 to 14. Tumor enhancement was optimally visualized on postoperative days 3 to 5. Nine of 10 patients (90%) with gross residual enhancing tumor showed an increase of enhancing tumor size during the study. Methemoglobin was detected at some time in all patients (100%) and was usually minor, but in six (35%) it interfered with residual tumor assessment. The 97 doses of Gd-DTPA, administered in 17 patients, were well tolerated.
  
  
  CONCLUSIONS
  When accurate assessment of residual enhancing tumor is needed in patients with malignant glioma, an MR scan performed on postoperative days 3 to 5 should minimize the confounding effects of postsurgical enhancement and methemoglobin. The repeated administration of Gd-DTPA over several weeks is well tolerated.
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Alberta, Canada. peter.forsythe@cancerboard.ab.ca
authors.forename: P A
authors.initials: PA
authors.lastname: Forsyth
authors.forename: E
authors.initials: E
authors.lastname: Petrov
authors.forename: H
authors.initials: H
authors.lastname: Mahallati
authors.forename: J G
authors.initials: JG
authors.lastname: Cairncross
authors.forename: P
authors.initials: P
authors.lastname: Brasher
authors.forename: M E
authors.initials: ME
authors.lastname: MacRae
authors.forename: N A
authors.initials: NA
authors.lastname: Hagen
authors.forename: P
authors.initials: P
authors.lastname: Barnes
authors.forename: R J
authors.initials: RJ
authors.lastname: Sevick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage; D001932:Brain Neoplasms / Q000473:pathology* / Q000601:surgery; D003287:Contrast Media; D003907:Dexamethasone / Q000008:administration & dosage; D005260:Female; D005910:Glioma / Q000473:pathology* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology; D008875:Middle Aged; D018365:Neoplasm, Residual; D011184:Postoperative Period; D011446:Prospective Studies
chemical_list: D000893:Anti-Inflammatory Agents; D003287:Contrast Media; D003907:Dexamethasone