A small tabletop stationary five-degree of freedom device such as a “
robot” 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.