A method of preplanning for guided medical procedures includes obtaining a first 3D diagnostic dataset for a region of interest of a subject. This first dataset can be a non-stereotactic dataset and provide sufficient contrast to identify target tissue in the region of interest. A treatment preplan is developed to treat the target tissue using the first dataset exclusive of stereotactic data. The treatment preplan includes placement locations for a plurality of initial radiation beams and their respective dose intensities. A second, stereotactic 3D dataset can be obtained for the region of interest. A registered dataset can then be created by registering the first dataset to the second dataset. The treatment preplan can be modified using data associated with the registering step to generate a stereotactic treatment plan including a plurality of radiation treatment beams with respective placement positions based on the registered dataset to treat the target tissue.