Patent Number: 
Section: claims

1. A computed tomography (CT) scanner comprising:a gantry having an opening therein to receive a subject to be scanned;an x-ray source disposed within the gantry and configured to project a cone beam of x-rays at the subject during CT data acquisition;a detector array configured to detect x-rays passing through the subject;a dynamic collimator disposed near the x-ray source; anda controller configured to:rotate the x-ray source about the subject, wherein a single rotation of the x-ray source is divided into a first half-scan and a second half-scan;acquire a first set of imaging data during the first half-scan;acquire a second set of imaging data during the second half-scan;position the dynamic collimator after acquiring image data from one of the first half-scan and the second half-scan and simultaneous to the commencement of acquiring image data from the other of the first half-scan and the second half-scan, wherein the dynamic collimator is configured to obstruct a central portion of an x-ray beam emitted by the x-ray source during one of the first half-scan and the second half-scan; andreconstruct a CT image using the first set of imaging data and the second set of imaging data. 2. The CT scanner of claim 1 further comprising a bowtie filter disposed near the x-ray source to absorb low-energy photons prior to reaching the subject, wherein the controller is configured to position the dynamic collimator between the x-ray source and the bowtie filter. 3. The CT scanner of claim 1 wherein the dynamic collimator is formed of a material having high x-ray attenuation characteristics. 4. The CT scanner of claim 3 wherein the dynamic collimator is formed of tungsten. 5. The CT scanner of claim 1 wherein the dynamic collimator comprises a single element configured to obstruct a portion of the x-ray beam. 6. The CT scanner of claim 1 wherein the dynamic collimator is positioned a distance from the x-ray source so as to block only a central portion of the x-ray beam emitted by the x-ray source and allow outer portions of the x-ray beam to reach the subject. 7. The CT scanner of claim 1 wherein the dynamic collimator is configured to block 80 percent of the x-ray beam emitted by the x-ray source during the second half-scan. 8. The CT scanner of claim 1 wherein the controller is configured to rotate the x-ray source entirely about the subject within a single heartbeat of the subject. 9. The CT scanner of claim 1 wherein the controller is configured to reconstruct the CT image from the first set of imaging data and the second set of imaging data acquired from a full rotation of the x-ray source about the subject. 10. The CT scanner of claim 1 wherein the detector array is a multi-detector-row array. 11. A method of cardiac CT imaging, the method comprising:rotating an x-ray source through a series of projection angles about a scan subject along an annular path of rotation, wherein a single rotation of the x-ray source is divided into a first half-scan and a second half-scan;acquiring a first set of imaging data from the first half-scan;acquiring a second set of imaging data from the second half-scan;deploying a collimator after completion of image data acquisition from one of the first half-scan and the second half-scan and simultaneous to the commencement of image data acquisition from the other of the first half-scan and the second half-scan to block a central portion of an x-ray beam emitted by the x-ray source during one of the first half-scan and the second half-scan; andreconstructing a CT image using the first set of imaging data and the second set of imaging data. 12. The method of claim 11 further comprising defining a complimentary projection angle of the second half-scan for each projection angle of the first half-scan. 13. The method of claim 11 wherein the step of reconstructing a CT image comprises reconstructing an image using the first set of imaging data and the second set of imaging data acquired from a full rotation of the x-ray source about the scan subject. 14. The method of claim 11 further comprising fully rotating the x-ray source about the scan subject within a single heartbeat duration of the scan subject. 15. The method of claim 11 wherein the step of deploying the collimator comprises blocking 80 percent of the x-ray beam emitted by the x-ray source during the second half-scan. 16. A CT imaging system comprising:a rotatable gantry having an opening therein to receive a subject to be scanned;an x-ray source disposed within the rotatable gantry and configured to project a beam of x-rays at the subject during CT data acquisition;a collimator disposed near the x-ray source, wherein the collimator is configured to be moveably positioned into the path of the projected beam of x-rays; anda computer programmed to:fully rotate the x-ray source about the subject, wherein the rotation of the x-ray source is divided into a first half-scan and a second half-scan;acquire a first set of imaging data from the first half-scan;acquire a second set of imaging data from the second half-scan;moveably position the collimator to block a central portion of an x-ray beam emitted by the x-ray source after acquisition of imaging data from one of the first half-scan and the second half-scan, at commencement of acquisition of imaging data from the other of the first half-scan and the second-half scan, and during the entirety of acquisition of imaging data from the other of the first half-scan and the second half-scan; andreconstruct a CT image using the first set of imaging data and the second set of imaging data. 17. The CT system of claim 16 wherein the collimator is formed as a single unit having high x-ray attenuation characteristics. 18. The CT system of claim 16 wherein the computer is further programmed to cause rotation of the gantry at a gantry speed such that the first half-scan and second half-scan occur within a single heartbeat duration. 19. The CT system of claim 16 wherein the computer is further programmed to define the first half-scan and the second half-scan such that an imaging volume of first half-scan partially overlaps the imaging volume of the second half-scan. 20. The CT system of claim 16 wherein the collimator is sized and disposed a distance from the x-ray source such that the collimator blocks only a central portion of the x-ray beam emitted by the x-ray source at the subject during the second half-scan.