To allow the experimental use in rats of a Gamma Knife Radiosurgical U
nit, a stereotactic device adapted from the conventional Kopf's device
was developed. To control the accuracy of the coordinate system based
on the De Groot's rat stereotactic atlas, experimental radiosurgical
lesions were made on the left striatum. The isodose curve distribution
of the 4 mm collimator was calculated with the dose planning software
used in Gamma Knife and superimposed on the left striatum target. Dos
es of 200 Gy were administred to the left striatum in six rats. The re
sults were evaluated 21, 34 and 47 days later. At 34 and 47 days necro
tic lesions were exactly as targeted. In a second group of 48 rats rec
eiving a doses of 100 Gy, no lesions were observed after 7, 15, 24, 31
, 45 days. However, in all rats sacrified 59, 72 and 90 days after day
radiation, a necrotic lesion was always present and confirmed that at
each time the lesions were precisely targeted. This apparatus allows
precise and reproducible gamma irradiation lesion in rat brain without
expensive and time consuming imaging techniques. This device provides
a useful system to observe the experimental effects of radiosurgery o
n the central nervous system in rats.