Since acquiring the Perfection Gamma Knife system, we have encouraged patients scheduled for GKS to have their treatment MRI several days in advance, with the images subsequently imported and fused to the ''day of treatment'' CT scan with the frame in position. This offers several advantages compared to obtaining the MRI on the day of treatment, including the following: This allows an accurate definition of the number, size and location of all of the metastasis. This allows functional MRI to be performed to help distinguish radiation necrosis or change from metastasis enlargement, especially if there has been prior GKS or radiation. 

     Our experience has led to this practice now being our standard, and we will present specific examples to illustrate these principles.

     

     

     

     

     This allows treatment planning in advance to save valuable time on the day of treatment, which is especially important in complex cases with multiple metastasis. 

     The primary disadvantage is potential patient motion because of the lack of frame stability.