Patent Number: 
Section: claims

1. A collimator system for reducing radiation comprising:a collimator comprising:at least one aperture configured to allow radiation to pass through;wherein thickness and material of said collimator are designed to pass a part of said radiation passing through area outside said at least one aperture; anda motorized member associated with said collimator, said motorized member is configured to move said collimator in a 2-dimensional plane; said motorized member is configured to rotate between an x-ray source's pulses and stop during said x-ray source's pulses. 2. The collimator system of claim 1, further comprising at least one outer annulus and at least one inner annulus, each said at least one inner annulus between a respective one of said at least one aperture and a respective one of said at least one outer annulus, each said at least one inner annulus having changing thickness. 3. The collimator system of claim 2, wherein each said inner annulus thickness changes as a function of the distance from said inner annulus respective aperture, starting at a low thickness on the side of said respective aperture and ending at the thickness of said inner annulus respective outer annulus on the side of said respective outer annulus. 4. The collimator system of claim 1, wherein said motorized member comprises at least one of carriages movable along a track. 5. The collimator system of claim 4, wherein said at least one carriage comprises two carriages, each carriage is movable along one of two non-parallel tracks. 6. A variable aperture collimator system comprising:a plurality of radiation attenuating plates, each one of said plates having an aperture; wherein thickness and material of said radiation attenuating plates are designed to pass a part of said radiation passing through area outside said at least one aperture;means for selecting a radiation attenuating plate;a collimator having an opening configured to receive any of said plurality of radiation attenuating plates; anda plate changing mechanism comprising:a body comprising on one face thereof said plurality of said radiation attenuating plates;said body configured to move to bring a selected plate to said opening of said collimator. 7. The variable aperture collimator system of claim 6, wherein said body is highly transparent to radiation. 8. The variable aperture collimator system of claim 6, wherein said body has one of: a circular shape and an anchor like shape. 9. The variable aperture collimator system of claim 6, wherein said radiation attenuating plates are made of copper. 10. A method of controlling a Region of Interest (ROI) in an image of an x-ray irradiated area, comprising:providing:a collimator comprising:at least one aperture configured to allow radiation to pass through;wherein material and thickness of said collimator are designed to pass a part of said radiation passing through area outside said at least one aperture; anda motorized member associated with said collimator, said motorized member is configured to move said collimator in a 2-dimensional plane in two independent directions;determining a location on said image; andmoving said motorized member, thereby moving said collimator to place at least one of said at least one aperture according to said determined location. 11. The method of claim 10, further comprising:providing:a plurality of radiation attenuating plates, each one of said plates having an aperture;means for selecting a radiation attenuating plate; anda plate changing mechanism comprising:a body comprising on one face thereof said plurality of radiation attenuating plates;wherein said at least one aperture of said collimator comprises one aperture configured to receive any of said plurality of radiation attenuating plates; andmoving said body to bring a selected one of said plurality of radiation attenuating plates to said aperture of said collimator. 12. The method of claim 10, wherein said collimator further comprises at least one outer annulus and at least one inner annulus, each said at least one inner annulus between a respective one of said at least one aperture and a respective one of said at least one outer annulus, each said at least one inner annulus having changing thickness. 13. The method of claim 12, wherein each said inner annulus thickness changes as a function of the distance from said inner annulus respective aperture, starting at a low thickness on the side of said respective aperture and ending at the thickness of said inner annulus respective outer annulus on the side of said respective outer annulus. 14. The method of claim 10, wherein said motorized member comprises at least one carriages movable along a track. 15. The method of claim 14, wherein said at least one carriage comprises two carriages, each carriage is movable along one of two non-parallel tracks. 16. The method of claim 10, wherein said at motorized member is configured to rotate between an x-ray source's pulses and stop during said x-ray source's pulses. 17. The method of claim 11, wherein said body is highly transparent to radiation. 18. The method of claim 11, wherein said body has one of: a circular shape and an anchor like shape. 19. The method of claim 11, wherein said radiation attenuating plates are made of copper.