title: Experimental analysis of radiation dose distribution in radiosurgery. II. Dose fall-off outside the target volume.
abstract: BACKGROUND
  The role of radiation dose delivered to surrounding tissues outside target is often minimized in radiosurgery. We study histopathological effects of dose fall-offs outside the target using an experimental model of trigeminal nerve irradiation in the rat.
  
  
  METHODS
  Sixteen rats were irradiated with a Gamma Knife at the right trigeminal nerve using a 90-Gy dose and 4 different gradients of dose fall-off; the brainstem at the trigeminal nerve root entry was histologically analyzed 3 months after irradiation.
  
  
  RESULTS
  Four specific histopathological reactions were found as a consequence of the irradiation. All these reactions were significantly related to the gradient of dose fall-off.
  
  
  CONCLUSIONS
  Different dose distributions outside the target could produce various histological effects in the irradiated tissue that could influence the outcome of radiosurgical treatment. A more rapid fall-off of dose (higher selectivity) is associated with less risk of histological changes in tissues surrounding the target.
authors.affiliation: Gamma Knife Center, Erasme University Hospital, Brussels, Belgium. nmassage@ulb.ac.be
authors.forename: Nicolas
authors.initials: N
authors.lastname: Massager
authors.forename: Calliope
authors.initials: C
authors.lastname: Maris
authors.forename: Ouzi
authors.initials: O
authors.lastname: Nissim
authors.forename: Daniel
authors.initials: D
authors.lastname: Devriendt
authors.forename: Isabelle
authors.initials: I
authors.lastname: Salmon
authors.forename: Marc
authors.initials: M
authors.lastname: Levivier