title: Diffusion-weighted MR imaging abnormalities in pediatric patients with surgically-treated intracranial mass lesions.
abstract: BACKGROUND
  Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) technique that measures the degree of water diffusion in vivo. DWI abnormalities are frequently observed on immediate postoperative imaging following surgical resection of gliomas in adults. These abnormalities subsequently demonstrate contrast enhancement, which may be confused with lesion recurrence. The purpose of this study was to investigate the occurrence of these postoperative abnormalities in pediatric patients with intracranial mass lesions.
  
  
  METHODS
  Thirty-three consecutive patients <or=18 years old with a newly diagnosed intracranial mass lesion underwent MRI, including DWI, before and immediately after surgical treatment.
  
  
  RESULTS
  The median patient age was 9.9 years (range 0.2-18 years). Supratentorial and infratentorial lesions were identified in 22 and 11 patients, respectively. Infiltrative and noninfiltrative, as well as benign and malignant lesions, were included. Postoperative imaging demonstrated areas of reduced diffusion adjacent to the resection cavity in 20 (61%) cases. The median volume of these areas was 1.7 cm3 (range 0.3 cm3-12.0 cm3). Subsequent imaging studies in 9 of the 18 cases showed contrast enhancement in the area corresponding to the DWI abnormality. There were no clinical deficits attributable to any of the diffusion abnormalities. There was no association between the occurrence of these abnormalities and whether the lesion was infiltrative, non-infiltrative, benign, or malignant.
  
  
  CONCLUSIONS
  DWI abnormality on immediate postoperative MRI is common following surgery for newly diagnosed intracranial mass lesions in pediatric patients. Focal contrast enhancement in the postoperative period may be confused with recurrence for some lesions. Our study suggests that immediate postoperative DWI is useful in interpreting new areas of focal contrast enhancement on subsequent imaging in children who have had surgery for brain tumors.
authors.affiliation: Department of Neurological Surgery, Brain Tumor Research Center, San Francisco school of medicine, University of California, San Francisco, CA 94143-0112, USA. jsmith1enator@gmail.com
authors.forename: Justin S
authors.initials: JS
authors.lastname: Smith
authors.forename: Henry
authors.initials: H
authors.lastname: Lin
authors.forename: Mary Catherine
authors.initials: MC
authors.lastname: Mayo
authors.forename: Anuradha
authors.initials: A
authors.lastname: Bannerjee
authors.forename: Nalin
authors.initials: N
authors.lastname: Gupta
authors.forename: Victor
authors.initials: V
authors.lastname: Perry
authors.forename: Soonmee
authors.initials: S
authors.lastname: Cha
mesh_terms: D000293:Adolescent; D001921:Brain / Q000000981:diagnostic imaging* / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D038524:Diffusion Magnetic Resonance Imaging; D004487:Edema / Q000000981:diagnostic imaging / Q000209:etiology; D005260:Female; D006801:Humans; D007223:Infant; D015192:Infratentorial Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D019635:Neurosurgical Procedures / Q000009:adverse effects; D011184:Postoperative Period; D011859:Radiography; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D015173:Supratentorial Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery