Experimental analysis of radiation dose distribution in radiosurgery. II. Dose fall-off outside the target volume.
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.
Massager
Nicolas
N
Gamma Knife Center, Erasme University Hospital, Brussels, Belgium. nmassage@ulb.ac.be
Maris
Calliope
C
Nissim
Ouzi
O
Devriendt
Daniel
D
Salmon
Isabelle
I
Levivier
Marc
M