Patent ID: 7474736

Claim:
A radiation method, comprising: moving a filter to a first position relative to a radiation source to obtain a first set of image data, the filter having an axis, a first cross sectional shape at a first point along the axis, and a second cross sectional shape at a second point along the axis, the first cross sectional shape being the same as the second cross sectional shape, wherein the filter has end portions that are thicker than a mid portion, the end portions being fixed in position relative to each other, and wherein the filter is made from a material that is partially transparent to radiation; and moving the filter to a second position relative to the radiation source to obtain a second set of image data; wherein the filter is moved to the first position relative to the radiation source based on a first gantry position of the radiation source; and wherein the radiation source is capable of movement within a plane, and the filter is moved by a positioner to the first position in a direction that is parallel to the plane.