Patent Number: 
Section: claims

1. A collimator for providing collimation of radiation from at least one radiation source, the collimator comprising radiation attenuating material and featuring a twisted slit comprising radiation transmissive material, wherein the twisted slit comprises first and second apertures configured to provide a series of compound apertures from a radiation entry point in one aperture to a radiation exit point in the other aperture,wherein the collimator substantially takes the form of a prolate spheroid body having a major axis that passes through its longest dimension, the first aperture extending at least partially around the body in a plane orthogonal to the major axis and the second aperture extending at least partially around the body in a spiral form relative to the major axis such that all direct pathways from an entry point to an exit point and passing through the major axis at a predetermined angle, are of constant length in order to provide constant collimation effect. 2. A collimator according to claim 1 configured to rotate about the major axis. 3. A collimator according to claim 1 wherein the first aperture incorporates a recess which completely circumnavigates the body, the recess suitable for confining at least one radiation source or detector. 4. A collimator according to claim 1 wherein the radiation transmissive material comprises air. 5. A collimator according to claim 1 wherein the radiation attenuating material comprises tungsten. 6. A method of generating a scanning beam of radiation, the method comprising the steps of:providing a collimator in accordance with claim 1;providing at least one divergent radiation source fixed stationary relative to the collimator and substantially positioned within the first aperture; androtating the collimator about the major axis such that the compound aperture through the collimator from the position of the at least one divergent radiation source, changes, thereby generating a scanning beam.