a tomographic scanner includes an imaging device for obtaining images of the anatomy of a patient . a localizer device such as an articulated arm includes a base portion mounted in a fixed relationship to the imaging device and a free end adapted for selective movement into varied positions near a patient body disposed on the imaging device . a guide device such as grid lattice is attached to the free end of the arm . a position transducer associated with the localizer device generates information as to the position of the localizer and hence the position of the guide device in scanner coordinates . the guide device contains a plurality of needle guides . the position of the guide device is displayed in relation to images of the anatomy of the patient . this information is used by the operator to guide the insertion of brachytherapy seeds in a desired pattern and location in relation to the anatomy of the patient .