A small tabletop stationary five-degree of freedom device such as a ā
robotā is used to define the treatment region by tracing the region under direct
visualization and then to precisely deliver the
treatment plan created by an automatic planning
system by positioning a single low energy
radiation source, or a plurality of low energy sources connected to each other in a predetermined parallel or similar geometry, each source equipped with blocking and attenuation mechanisms, at a plurality of positions in a planar fashion across or through a selected
treatment field, thereby delivering a plurality of parallel overlapping beams indexed on a
millimeter or submillimeter grid such that a concentration of
dose is achieved at a variable depth in tissue relative to the
dose where the
radiation first enters the tissue and can be used to treat regions on or below the surface of tissue, in a cavity and underlying region created following a
surgical resection, on or below the surface of an
internal cavity, hollow viscus, or lumen, or deep in tissue adjacent to an inserted probe or conduit or
catheter. By generating a plurality of overlapping beams indexed on a
millimeter or submillimeter grid that converge on a target volume loaded with gold nanoparticles, a tumorcidal
dose of
radiation can be delivered in as little as a
single session to
tumor cells but not to normal cells within or outside the treatment volume. This approach also makes it possible to deliver serial radiosurgical treatments.