Polymer gel 3D dosimetry was used to confirm the accuracy of treatment plans produced by the treatment planning software and assess the dosimetric uncertainties of the radiosurgery procedures. The aim of this study is to investigate the 3D dose distribution of intensity-modulated radiosurgery(IMRS) treatment using polymer gel dosimeter for a selected radiosurgery case. A spherical glass flask(160mm-radius) filled with the polymer gel dosimeter was fixed with in the stereotactic head frame. And the intensity modulated radiosurgery(IMRS) treatment procedure was simulated to a selected preclinical concave shaped pituitary tumor closed to the optic pathway. Images of the gel dosimeter were acquired using a Simens 1.5T MR imager. The images transferred to a planning computer for which a data analysis and compare to dose distribution produced by planning software. Reasonable agreement was observed at medium and high doses (50%-80% isodose lines) although differences of up to 10% were observed at low doses (30% isodose line) between the treatment planning system calculation of relative dose distribution and the gel measured data. The gel dosimeter measured dose profiles of pre-planned beams agree within 3% with the beam profiles produced by planning software. The polymer gel dosimeter in combination with MR imaging has been shown to be a valuable devices for verifying three dimensional IMRS dose distribution.