Patent Number: 
Section: claims

1. For use with an irradiation system, a collimator comprising:an inner border whose inner perimeter defines an aperture;an outer border positioned outwards of said inner border, an enclosure being defined and bounded between said inner and outer borders, said enclosure being sufficiently filled with a radiopaque pliable material so as to block a predefined amount of radiation from passing through said enclosure, while allowing radiation to pass through said aperture; andat least one actuator attached to at least one point of said inner border operable to deform said inner border so as to modify a shape of said aperture; andapparatus for determining position and shape of said aperture, wherein said apparatus comprises a camera. 2. The collimator according to claim 1, wherein said radiopaque pliable material comprises a radiopaque liquid. 3. The collimator according to claim 1, wherein said radiopaque pliable material comprises a radiopaque powder. 4. The collimator according to claim 1, wherein said radiopaque pliable material comprises a dispersion of powdered radiopaque material in a carrier. 5. The collimator according to claim 1, wherein said radiopaque pliable material comprises a radiopaque gas. 6. The collimator according to claim 1, wherein said inner border is constructed of a flexible material. 7. The collimator according to claim 1, further comprising a sensor that senses a parameter related to irradiation, said sensor being in operative communication with said at least one actuator, wherein said at least one actuator changes the shape of said aperture in accordance with information sensed by said sensor. 8. An irradiation system comprising:a radiation source that emits a radiation beam; anda collimator that collimates the radiation beam, said collimator comprising an inner border whose inner perimeter defines an aperture; an outer border positioned outwards of said inner border, an enclosure being defined and bounded between said inner and outer borders, said enclosure being sufficiently filled with a radiopaque pliable material so as to block a predefined amount of radiation from passing through said enclosure, while allowing radiation to pass through said aperture; and at least one actuator attached to at least one point of said inner border operable to deform said inner border so as to modify a shape of said aperture. 9. The irradiation system according to claim 8, wherein said collimator is mounted on a movable interface at an output of said radiation source, said movable interface being operable to receive target positional data and accordingly move said collimator and said aperture relative to said radiation source.