Patent Number: 
Section: claims

1. A radiation CT imaging system, comprising:a radiation source arranged on a first side of a scan gantry the radiation source configured to emit radiation rays to the subject;a collimator disposed between the subject and the radiation source, the collimator configured to beamform the radiation rays from the radiation source, wherein the collimator comprises a planar gating device comprising at least one slit for passage of the radiation rays; anda radiation detector disposed on a second side of the scan gantry, the second side being opposite the first side, the radiation detector configured to detect the radiation rays transmitted;wherein the radiation detector comprises a plurality of detector elements arranged in a row, and there is an inclination angle between adjacent detector elements,andwherein a width distribution of each of the at least one slit in the longitudinal direction of the collimator is determined jointly by the following: a vertical distance between a focus of the radiation source and the slit, a vertical distance between the focus and the radiation detector, the inclination angle between adjacent detector elements, a length of each detector element, a desired width of projection on the radiation detector formed by the radiation rays passing through the slit, and an offset angle of a connecting line from a point on a longitudinal center line of the slit to the focus relative to a plane passing the focus and perpendicular to the slit. 2. The radiation CT imaging system according to claim 1, wherein the plurality of detector elements comprises three to seven detector elements. 3. The radiation CT imaging system according to claim 1, wherein the radiation rays are X-rays. 4. The radiation CT imaging system according to claim 3, wherein the plurality of detector elements comprises three to seven detector elements. 5. The radiation CT imaging system according to claim 1, further comprising:a collimator controller configured to select one of said plurality of slits. 6. The radiation CT imaging system according to claim 1, wherein the plurality of detector elements have a same or a different length. 7. The radiation CT imaging system according to claim 1, wherein the inclination angles between adjacent detector elements is equal. 8. The radiation CT imaging system according to claim 1, wherein the inclination angle between selected pairs of adjacent detector elements is not equal. 9. A method for determining a slit profile of a CT collimator, wherein the CT collimator comprises a planar gating device comprising at least one slit to allow radiation rays from a radiation source to be used in cooperation with the CT collimator to pass through and projected onto a radiation detector to be used in cooperation with the CT collimator, wherein the radiation detector comprises a plurality of detector elements arranged in a row, and there is an inclination angle between two adjacent detector elements, the method comprising:determining for each slit of the at least one slit a profile of two opposite edges in a longitudinal direction of the selected slit based on the following: a vertical distance between a focus of the radiation source to the slit, a vertical distance between the focus and the radiation detector, the inclination angle between adjacent detector elements, a length of each detector element, a desired width of projection on the radiation detector by the radiation rays passing through the slit, and an offset angle of a connecting line from a point on a longitudinal center line of the slit to the focus relative to a plane passing the focus and perpendicular to the slit. 10. The method according to claim 9, wherein the plurality of detector elements comprises three to seven detector elements. 11. The method according to claim 9, wherein the radiation rays are X-rays. 12. The method according to claim 9, wherein the plurality of detector elements have a same or a different length. 13. The method according to claim 9, wherein the inclination angles between adjacent detector elements is equal. 14. The method according to claim 9, wherein the inclination angle between selected pairs of adjacent detector elements is not equal.