An assembly of devices designed to deliver a therapeutic radiation dose to an anatomical region from external beams produced from multiple radionuclide sources arranged in a fixed focal point collimated array; typically used to treat brain, neck, breast and spinal tumours. It typically consists of: 1) a stereotactic positioning device attached to the patient to define the three-dimensional (3-D) co-ordinates of the treatment site; 2) fixed diameter collimators; 3) high-density beam blockers; 4) a shielded housing to hold the sources, reducing room radiation; 5) a precision aligned array to cause the source beams to intersect at a single point; and 6) a moveable patient table.