title: Lesion evolution after gamma knife irradiation observed by magnetic resonance imaging.
abstract: OBJECTIVE
  Our study is focused on the magnetic resonance imaging (MRI) observation of lesion development and hippocampus related functional impairments in rats after irradiation with a Leksell Gamma knife (LGK).
  
  
  METHODS
  We exposed 32 three-month-old Long-Evans rats to various radiation doses (25 Gy, 50 Gy or 75 Gy). The rats were scanned by a 4.7 T magnetic resonance (MR) spectrometer at several timepoints (1 - 18 months) after irradiation. The lesion size was evaluated by manual segmentation; the animals were behaviorally tested in a Morris water maze and examined histologically.
  
  
  RESULTS
  We found that a dose of 25 Gy induced no edema, necrosis or behavioral change. The response of the rats to higher doses was not uniform; the first occurrence of lesions in the rat brains irradiated with 50 and 75 Gy was detected six months post-irradiation. Functional impairment correlated well with the lesion size and histology.
  
  
  CONCLUSIONS
  Rat brains showed the development of expanding delayed lesions after 50 or 75 Gy doses from the LGK during the first year after irradiation.
authors.affiliation: MR Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic.
authors.forename: D
authors.initials: D
authors.lastname: Jirák
authors.forename: K
authors.initials: K
authors.lastname: Námĕstková
authors.forename: V
authors.initials: V
authors.lastname: Herynek
authors.forename: R
authors.initials: R
authors.lastname: Liscák
authors.forename: J
authors.initials: J
authors.lastname: Vymazal
authors.forename: V
authors.initials: V
authors.lastname: Mares
authors.forename: E
authors.initials: E
authors.lastname: Syková
authors.forename: M
authors.initials: M
authors.lastname: Hájek
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000209:etiology / Q000473:pathology; D004307:Dose-Response Relationship, Radiation; D006624:Hippocampus / Q000293:injuries* / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology* / Q000473:pathology*; D016634:Radiosurgery / Q000009:adverse effects*; D051381:Rats; D020318:Rats, Long-Evans