Auxiliary collimating device for obtaining irradiation fields of any shape for high energy radiotherapy apparatus

Claim 2

An auxiliary collimating device for obtaining irradiation fields of any shape for irradiation apparatus provided with a source of highenergy particles and a main collimator, said auxiliary collimating device comprising a first container, termed a master container, and a second container, termed a localising container, said containers being integral with a chassis movable along guide rails; said containers being interconnected by a flexible pipe; said master container being, in a position of rest, filled with mercury ; said localising container containing a block of expanded polystyrene of predetermined shape; said block having lateral walls converging toward said source of particles; the block having cross-section the dimensions of which are homothetic to the dimensions of the field to be irradiated midway of the depth of the volume to be treated.

Claim 3

An auxiliary collimating device as claimed in claim 1, wherein said master-container and said localising container are associated with first shifting means for imparting to said containers a vertical movement at two pre-selected speeds, said movements allowing a suitably positioning of said containers for an irradiation shooting successively downwardly and upwardly, the high-speed travel enabling said localising container to be placed rapidly substantially in the region of its working position and the low-speed travel enabling said localising container to be positioned with precision against said main collimator; said master container being associated with second shifting means for placing said master container filled with mercury in a predetermined upper position with respect to the localising container so as to allow the mercury contained in the master container to enter the localising container and fill the volume left free by said polystyrene block disposed in said localising container.

Claim 4

An auxiliary collimating device according to claim 1, wherein said mercury contained in said master container is covered with water and there is disposed between said master container and said localising container an auxiliary container containing water which is adapted to be supplied to the localising container so as to cover the mercury contained in the localising container.

Claim 5

An auxiliary collimating device according to claim 1, wherein said expanded polystyrene block is adhered to a methyl polymethacrylate plate whereby said block may be positioned with precision in said localising container, the thickness of the assembly formed by said plate and said block being less than the height of said container.