title: MR imaging of pituitary adenomas after gamma knife stereotactic radiosurgery.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the response of pituitary adenomas to radiosurgery as manifested by changes in size and appearance on serial MR imaging.
  
  
  METHODS
  Over a mean follow-up period of 36 months, changes in 44 pituitary adenomas were assessed on 147 enhanced MR imaging studies. Prior surgery had been performed in 36 tumors (82%).
  
  
  RESULTS
  At the time of radiosurgery, mean tumor volume was 5.9 +/- 0.8 cm(3) (mean diameter, 2.2 cm). The mean reduction in volume at last follow-up was 41% (+/- 5%, p < 0.001), and a decrease in tumor volume of 25-100% was observed in 34 tumors (77%). Mean reduction in tumor volume at 6 months after radiosurgery was 9% (p = 0.095); at 1 year, 24% (p < 0.001); at 2 years, 34% (p < 0.001); at 3 years, 41% (p < 0.001); and at 4 years, 50% (p = 0.008). Six months after radiosurgery a slight and transient increase in size was observed in 21% of tumors. During follow-up, neither decreased contrast enhancement nor cyst development was associated with changes in tumor volume.
  
  
  CONCLUSIONS
  Tumor control was observed for most pituitary adenomas after radiosurgery and occurred gradually over a period of several years. A small increase in tumor size might be observed in the first 6 months after radiosurgery. In most cases, reductions in tumor size were not accompanied by a change in contrast enhancement or cyst formation.
authors.affiliation: Department of Diagnostic Imaging, Brown University School of Medicine, Rhode Island Hospital, 593 Eddy St., Providence, RI 02903, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Tung
authors.forename: G
authors.initials: G
authors.lastname: Noren
authors.forename: J M
authors.initials: JM
authors.lastname: Rogg
authors.forename: I M
authors.initials: IM
authors.lastname: Jackson
mesh_terms: D000236:Adenoma / Q000473:pathology* / Q000601:surgery*; D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000473:pathology* / Q000601:surgery*; D011182:Postoperative Care; D016634:Radiosurgery