Patent ID: 8368042
Filing Date: 2013-02-05
Classification: A61N

Abstract:
1. A method for modulating a radiation beam toward a target, comprising; rotating a radiation beam gantry and/or a target through an arc segment while irradiating the target with the radiation beam; placing a physical wedge in a beam path of said radiation beam to modify at least one of a beam aperture and a beam intensity of said radiation beam while rotating through said arc segment; and modifying at least one of a wedge angle and a wedge orientation of said physical wedge during a temporal increment associated with said arc segment, wherein said temporal increment comprises five sequential sub-increments defined as: 1) Pre-position—wherein said wedge is at rest outside a treatment field; 2) Approaching—wherein said wedge moves toward a desired position; 3) Wedging—wherein said wedge is in the desired position; 4) Clearing—wherein said wedge moves away from the desired position; and 5) Post-position—wherein said wedge is at rest outside the field, wherein wedge angle is determined by times of the sub-increments; And comprising modifying said wedge orientation by rotating said wedge about a rotational axis intersecting said wedge, and wherein Moving is a combination of the Approaching and Clearing sub-increments, and a ratio for finite Moving time (A′) is calculated from; R=ratio of a duration of a time slot to the temporal increment, wherein said time slot duration depends on an open field dose rate, a wedge attenuation profile and the Moving time A=ratio of Wedging time to open field time for ideal positioning, and (a) Temporal increment =wedging time +open field time and A′ is calculated as: