Support structure for electron accelerator with deflecting means and target and cooperating patient support

Claim 1

Radiotherapy apparatus capable of directing a beam of ionizing radiation from a multitude of directions onto a portion of an object to be irradiated, said apparatus comprising a high energy linear accelerator for producing a beam of high energy particulate radiation including particles having different energy levels; particulate radiation deflecting means for deflecting particulate radiation emanating from said accelerator through an angle of approximately 270* in one direction back across the path of said particulate radiation emanating from said accelerator for focusing said particulate radiation onto a target reactive with said particulate radiation to produce ionizing radiation, the sum of all the deflecting forces applied to any given particle of said particulate radiation being substantially proportionate to the energy of that particle in order to deflect all of said particles within a predetermined range of energy levels through substantially the same angle; collimation means for directing said ionizing radiation along a beam axis; movable shielding means for defining the cross-sectional area of the beam of ionizing radiation; a light source; means for directing light from said source through said movable shielding means onto the area to be irradiated to indicate visibly the size of the area irradiated; said target, deflecting means, collimating means, movable shielding means, light source and said light directing means being carried by an irradiation head from which said ionizing radiation emanates along said beam axis; a gantry mounting said linear accelerator and said irradiation head for rotation in a generally vertical plane about a second axis which is spaced from said head and traverses the path of said beam axis at a preselected point, said gantry maintaining the point at which said particulate radiation is focused onto said target at a fixed distance from said preselected point at all positions of rotation of said head about said second axis; a holding member for positioning the portion of the object to be irradiated at said preselected point at which said second axis traverses said beam axis, said holding member being mounted by a support means for rotation with respect to said irradiation head on a generally vertical axis passing through said point, said support means for holding member including a base which is spaced a greater distance from said second axis than said irradiation head whereby said head is rotatable between said holding member and said base, said support means further including a supporting column connecting said base and said holding member at a location outside the path of travel of said gantry and said irradiation head between said holding member and said base and means for adjusting the location of said holding member in the direction of said axis about which said holding member is rotatable to enable adjustment of the location of said holding member with respect to said preselected point.