The purpose of this study was to estimate the effect of gamma knife surgery by co-registration of follow-up image studies with stereotactic image obtained at gamma knife treatment. The treatment dose distribution can be shown at the follow-up image and the relation of post-treatment effect and treatment parameters can be found.

     We choose the cases with follow up duration more than two years for presentation. Six of pituitary adenomas and seven of C-P angle tumors were follow-up with Co-registration using Gamma Knife stereotactic radiosurgery systems between July 2007 and November 2007.The mean patient age was 47.8 years (range 27–71 years).

     First get to compute the corresponding position in the MRI image study to co-registration. We choose different kinds of visualization to run the automatic co-registration and no need to define any anatomical landmarks. After wait a working time, getting a reference study and we can also manual to align from reference study and then press the verity to complete image co-register study. About Co-registration image of pituitary adenoma (Figure 1), describes 45 years of patients were treated by transsphenoidal adenomectomy, residual lesions were located in the pituitary, extend to the cavernous sinus and clivus. The volume of the tumors ranged between 5.7 cm3. The median marginal tumor dose was 15Gy at 50%.Another co-registration image of C-P angle (Figure 2), using the same way revealed shrinkage tumor.

     This case of tumor progression has been shown during the follow-up periods, compare with co-registration image, therapy achieving the actuarial tumor control rate at present. Figures will be shown as below:

     This is a retrospective study.

     This co-registration analysis was conducted to evaluate the clinical results of GKS.