1. A localizer system that can be placed in a fixed spacial relationship to a body to be scanned by a scanning apparatus that produces scan images in which target images of a physical target in the body can be seen and can be related to specific coordinates of the physical target in the body relative to said localizer system, said localizer system comprising: A. a localizer having an axial axis, said localizer comprising: (i) at least twelve rod elements which lie on the edges of a right parallelapiped which can be defined mathematically in space relative to said localizer system; (ii) at least three side diagonal rod elements which are not parallel to any of said rod elements, but each of said side diagonal elements being parallel to at least one of the four planar axial sides of said parallelapiped which are parallel to said axial axis; (iii) at least one top diagonal rod element which lies in a plane that is perpendicular to said axial axis and which is not parallel to any of the edges of said parallelapiped; B. means for placing said localizer in a fixed relationship to the body to be scanned with the localizer axial axis being substantially parallel to the axis of the body to be scanned so that any reconstructed planar slice from a scan will lie in an arbitrary plane relative to the axes of said parallelapiped and intersect at least four of said rod elements and at least three of said diagonal elements and a slice image therefrom will contain identifiable image marks corresponding to the intersection of the planar slice with said elements, and so that if a target image is present in the slice image, the coordinates of the target in the body associated with said target image can be calculated.