title: Distinguishing recurrent intra-axial metastatic tumor from radiation necrosis following gamma knife radiosurgery using dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging.
abstract: OBJECTIVE
  MR image-guided gamma knife radiosurgery is often used to treat intra-axial metastatic neoplasms. Following treatment, it is often difficult to determine whether a progressively enhancing lesion is due to metastatic tumor recurrence or radiation necrosis. The purpose of our study was to determine whether relative cerebral blood volume (rCBV), relative peak height (rPH), and percentage of signal-intensity recovery (PSR) derived from dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging can distinguish recurrent metastatic tumor from radiation necrosis.
  
  
  METHODS
  Twenty-seven patients with systemic cancer underwent gamma knife radiosurgery for metastatic lesions of the brain and subsequently developed enlarging regions of enhancement within the radiation field. Subsequent surgical resection or clinicoradiologic follow-up established a diagnosis of recurrent metastatic tumor or radiation necrosis. Perfusion MR imaging datasets were retrospectively reprocessed, and regions of interest were drawn around the entire contrast-enhancing region. The resulting T2* signal-intensity time curves produced rCBV, rPH, and PSR values for each examination. A Welch t test was used to compare imaging values between groups.
  
  
  RESULTS
  The mean, minimum, and maximum PSR values were significantly lower (P < .01) in cases of recurrent metastatic tumor. The mean and maximum rCBV and rPH values were significantly higher (P < .02) in the recurrent metastatic tumor group.
  
  
  CONCLUSIONS
  The findings of our study suggest that perfusion MR imaging may be used to differentiate recurrent intra-axial metastatic tumor from gamma knife-induced radiation necrosis.
authors.affiliation: Department of Radiology, Neuroradiology Section; University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: R F
authors.initials: RF
authors.lastname: Barajas
authors.forename: J S
authors.initials: JS
authors.lastname: Chang
authors.forename: P K
authors.initials: PK
authors.lastname: Sneed
authors.forename: M R
authors.initials: MR
authors.lastname: Segal
authors.forename: M W
authors.initials: MW
authors.lastname: McDermott
authors.forename: S
authors.initials: S
authors.lastname: Cha
mesh_terms: D000230:Adenocarcinoma / Q000556:secondary / Q000601:surgery; D001932:Brain Neoplasms / Q000556:secondary / Q000601:surgery*; D001943:Breast Neoplasms / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000556:secondary / Q000601:surgery; D002292:Carcinoma, Renal Cell / Q000556:secondary / Q000601:surgery; D002294:Carcinoma, Squamous Cell / Q000556:secondary / Q000601:surgery*; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D011183:Postoperative Complications / Q000175:diagnosis*; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media