Patent Number: 
Section: claims

1. A shutter mechanism for collimating x-rays comprising:first and second parallel drive shafts spaced apart from one another;first and second parallel guide shafts spaced apart from one another, said drive shafts and guide shafts defining an aperture, with the axes of the drive shafts and guide shafts extending parallel to the edges of the aperture;a flexible transverse band sliding about the aperture with opposing first and second edges moving parallel to the axes of the drive shafts;a flexible longitudinal band sliding about the aperture with opposing first and second edges moving parallel to the axes of the guide shafts;a first cam driving the transverse band about the aperture;a second cam driving the longitudinal band about the aperture;a first transverse shutter made of an x-ray opaque material having a first end attached to the first edge of the transverse band and held in sliding engagement between the drive shafts to slide along the axes of the drive shafts;a second transverse shutter made of an x-ray opaque material having a first end attached to the second edge of the transverse band and held in sliding engagement between the drive shafts to slide along the axes of the drive shafts;a first longitudinal shutter made of an x-ray opaque material having a first end attached to the first edge of the longitudinal band and held in sliding engagement between the guide shafts to slide along the axes of the guide shafts; anda second longitudinal shutter made of an x-ray opaque material having a first end attached to the second edge of the longitudinal band and held in sliding engagement between the guide shafts to slide along the axes of the guide shafts. 2. The shutter mechanism of claim 1 wherein the cams are on the drive shafts. 3. The shutter mechanism of claim 1 wherein the transverse band slides about the aperture in a substantially rectangular path. 4. The shutter mechanism of claim 1 wherein the longitudinal band slides about the aperture in a substantially rectangular path. 5. The shutter mechanism of claim 1 wherein at least one of the shutters further comprises a shutter attachment extending from the first end of the shutter for attachment to one of the flexible bands. 6. The shutter mechanism of claim 5 wherein said shutter attachment further comprises a channel for sliding engagement with one of the drive shafts and the guide shafts. 7. The shutter mechanism of claim 1 wherein the guide shafts are orthogonal to the drive shafts to define said aperture. 8. A shutter mechanism for collimating x-rays comprising:first and second parallel drive shafts spaced apart from one another;first and second parallel guide shafts spaced apart from one another and orthogonal to said drive shafts, said drive shafts and guide shafts defining a rectangular aperture, with the axes of the drive shafts and guide shafts extending parallel to the edges of the aperture;a flexible transverse band sliding about the aperture with opposing first and second edges moving parallel to the axes of the drive shafts;a flexible longitudinal band sliding about the aperture with opposing first and second edges moving parallel to the axes of the guide shafts;a first cam on the first drive shaft driving the transverse band about the aperture in a substantially rectangular path;a second cam on the second drive shaft driving the longitudinal band about the aperture in a substantially rectangular path;a first transverse shutter made of an x-ray opaque material having a first end attached to the first edge of the transverse band and held in sliding engagement between the drive shafts to slide along the axes of the drive shafts;a second transverse shutter made of an x-ray opaque material having a first end attached to the second edge of the transverse band and held in sliding engagement between the drive shafts to slide along the axes of the drive shafts;a first longitudinal shutter made of an x-ray opaque material having a first end attached to the first edge of the longitudinal band and held in sliding engagement between the guide shafts to slide along the axes of the guide shafts; anda second longitudinal shutter made of an x-ray opaque material having a first end attached to the second edge of the longitudinal band and held in sliding engagement between the guide shafts to slide along the axes of the guide shafts. 9. The shutter mechanism of claim 8 wherein at least one of the shutters further comprises a shutter attachment extending from the first end of the shutter for attachment to one of the flexible bands. 10. The shutter mechanism of claim 9 wherein said shutter attachment further comprises a channel for sliding engagement with one of the drive shafts and the guide shafts. 11. A shutter mechanism for collimating x-rays comprising:first and second parallel drive shafts spaced apart from one another;first and second parallel guide shafts spaced apart from one another, said drive shafts and guide shafts defining an aperture, with the axes of the drive shafts and guide shafts extending parallel to the edges of the aperture;a flexible transverse band sliding about the aperture with opposing edges moving parallel to the axes of the drive shafts;a flexible longitudinal band sliding about the aperture with opposing edges moving parallel to the axes of the guide shafts;a first cam driving the transverse band about the aperture;a second cam driving the longitudinal band about the aperture;a pair of transverse shutters made of an x-ray opaque material held in sliding engagement between the drive shafts to slide along the axes of the drive shafts, each transverse shutter having a shutter attachment extending from a first end of the transverse shutter for attachment to opposing edges of the transverse band; anda pair of longitudinal shutters made of an x-ray opaque material held in sliding engagement between the guide shafts to slide along the axes of the guide shafts, said longitudinal shutter having a shutter attachment extending from a first end of the longitudinal shutter for attachment to opposing edges of the longitudinal band. 12. The shutter mechanism of claim 11 wherein said shutter attachment further comprises a channel for sliding engagement with one of the drive shafts and the guide shafts. 13. The shutter mechanism of claim 11 wherein the guide shafts are orthogonal to the drive shafts to define said aperture. 14. The shutter mechanism of claim 11 wherein the transverse band slides about said aperture in a substantially rectangular path. 15. The shutter mechanism of claim 11 wherein the longitudinal band slides about said aperture in a substantially rectangular path. 16. The shutter mechanism of claim 11 wherein the cams are on the drive shafts.