Patent Number: 
Section: claims

1. A collimator for a computed x-ray tomography imaging device, comprising a first grating and a second grating positioned on opposing sides of a primary radiation delivery window, the first and second gratings being part of separate first and second leaves, each of the first and second gratings comprising a plurality of attenuating members with a plurality of secondary radiation delivery windows extending between adjacent attenuating members of the first grating and the second grating, respectively, and wherein a width of each attenuating member is proportional to a distance between the attenuating member and the primary window. 2. The collimator of claim 1, wherein a width of each secondary window is less than a width of the primary window. 3. The collimator of claim 1, wherein a total area of each of the plurality of secondary windows is less than a total area of the primary window. 4. The collimator of claim 1, wherein a width of each secondary window is proportional to a distance between the secondary window and the primary window. 5. The collimator of claim 4, wherein the width of each secondary window is linearly proportional to the distance between the secondary window and the primary window. 6. The collimator of claim 1, wherein the width of each attenuating member is linearly proportional to the distance between the attenuating member and the primary window. 7. The collimator of claim 1, wherein the secondary windows comprise open passages extending through the grating. 8. The collimator of claim 1, wherein the secondary windows comprise panes of substantially radio-transmissive material. 9. The collimator of claim 1, wherein the attenuating members are oriented generally parallel to sides of the primary window. 10. The collimator of claim 1, wherein the secondary windows are oriented generally parallel to sides of the primary window. 11. The collimator of claim 1, wherein the first grating is movable relative to the second grating. 12. The collimator of claim 11, wherein the first and second gratings are independently movable. 13. A method of directing radiation during computed tomography (CT) imaging, comprising:emitting x-ray radiation from a radiation source toward an object;passing a first portion of the radiation through a primary window toward a target region in the object;passing a second portion of the radiation through at least one secondary window, on each of opposing sides of the primary window, to corresponding regions in the object outside the target region, where a width of each secondary window is less than a width of the primary window, rotating the radiation source and the primary and secondary windows about an axis, and translating the secondary windows relative to the primary window in a direction non-parallel to the axis;attenuating, between the primary and secondary windows, at least a third portion of the radiation; andgenerating CT image data based on the first and second portions of the radiation. 14. The method of claim 13, further comprising rotating the radiation source and the primary and secondary windows about an axis, and wherein radiation is passed through the primary window and the secondary windows while either (i) centers of the primary window and at least two of the secondary windows lie in a plane non-parallel to the axis or (ii) a plane intersecting the centers and the axis is non-parallel to the axis. 15. The method of claim 13, wherein the secondary windows are translated relative to the primary window during rotation of the radiation source. 16. The method of claim 15, wherein a first of the secondary windows is translated independently of a second of the secondary windows on an opposing side of the primary window from the first of the secondary windows. 17. The method of claim 13, wherein the attenuating comprises blocking passage of at least the third portion of the radiation between the primary and secondary windows. 18. A method of directing radiation during computed tomography (CT) imaging, comprising:emitting x-ray radiation from a radiation source toward an object;passing a first portion of the radiation through a primary window toward a target region in the object;passing a second portion of the radiation through at least one secondary window, on each of opposing sides of the primary window, to corresponding regions in the object outside the target region;attenuating, between the primary and secondary windows, at least a third portion of the radiation;rotating the radiation source and the primary and secondary windows about an axis, and translating the secondary windows relative to the primary window in a direction non-parallel to the axis; andgenerating CT image data based on the first and second portions of the radiation.