Patent Number: 
Section: claims

1. A method for imaging a region of interest (ROI) of an object using cone beam computed tomography, wherein a cone beam source is fixed with respect to a two dimensional detector, the method comprising the steps of: performing at least a first and a second circular scan along a first and a second extent, respectively, of a ROI within an object, wherein the cone beam source and detector are fixed such that during the first and second circular scans, one half of the detector area is used to acquire cone beam projection data corresponding to the ROI and a second half of the detector area is used to acquire cone beam projection data corresponding to a first and a second extended portion of the object, which extend beyond the first and second extents, respectively, of the ROI;  performing a line scan along the object connecting the first and second circular scans;  reconstructing the ROI by selectively combining the cone beam projection data corresponding to the ROI acquired from the first and second circular scans; and  reconstructing the first and second extended portions of the object using cone beam projection corresponding to the extended portions acquired from the first and second circular scans and cone beam data acquired from the line scan. 2. The method of  claim 1 , further comprising the step of combining the reconstructed ROI and first and second extended portions to obtain a reconstructed image of an extended ROI. claim 1 3. The method of  claim 1 , wherein the step of reconstructing the first and second extended portions comprises the steps of ramp filtering the corresponding cone beam projection data of the first and second circular scans and space variant filtering the projection data corresponding to the line scan. claim 1 4. The method of  claim 1 , wherein the step of reconstructing the ROI comprises augmenting missing Radon data from the first and second circular scans using the projection data acquired from the line scan. claim 1 5. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for imaging a region of interest (ROI) of an object using cone beam computed tomography, wherein a cone beam source is fixed with respect to a two dimensional detector, the method steps comprising: acquiring cone beam projection data from at least a first and second circular scan along a first and second extent, respectively, of a ROI within an object, wherein the cone beam source and detector are fixed such that during the first and second circular scans, one half of the detector area is used to acquire cone beam projection data corresponding to the ROI and a second half of the detector is used to acquire cone beam projection data corresponding to a first and a second extended portion of the object, which extend beyond the first and second extent, respectively, of the ROI;  acquiring cone beam projection data from a line scan along the object connecting the first and second circular scans;  reconstructing the ROI by selectively combining the cone beam projection data corresponding to the ROI acquired from the first and second circular scans; and  reconstructing the first and second extended portions of the object using cone beam projection corresponding to the extended portions acquired from the first and second circular scans and cone beam data acquired from the line scan. 6. The program storage device of  claim 5 , further comprising instructions for combining the reconstructed ROI and first and second extended portions to obtain a reconstructed image of an extended ROI. claim 5 7. The program storage device of  claim 5 , wherein the instructions for reconstructing the first and second extended portions comprise instructions for ramp filtering the corresponding cone beam projection data of the first and second circular scans and space variant filtering the projection data corresponding to the line scan. claim 5 8. The program storage device of  claim 5 , wherein the instructions for reconstructing the ROI comprise instructions for augmenting missing Radon data from the first and second circular scans using the projection data acquired from the line scan. claim 5 9. A method for imaging a region of interest (ROI) of an object using cone beam computed tomography, comprising the steps of: positioning an object to be imaged within a field of view between a cone beam point source and a two dimensional detector array, the cone beam point source and two dimensional detector being spatially fixed in relation to each other, wherein an axis of rotation v passes through the field of view and the object, wherein the cone beam point source is contained in a midplane that (i) is normal to the axis of rotation; (ii)is normal to a surface of the detector; and that (iii) intersects a center line of the detector that equally divides the detector area;  performing a first circular scan at various source positions along a first extent of a ROI of the object to acquire a first set of cone beam projection data by the detector;  performing a second circular scan at various source positions along a second extent of the object to acquire a second set of cone beam projection data by the detector, wherein the first and second extent of the object correspond to outer boundaries of a ROI along the rotation axis;  wherein the cone beam source and detector are fixed such that during the first and second circular scan, one half of the detector area is used to acquire cone beam projection data corresponding to the ROI and a second half of the detector area is used to acquire cone beam projection data corresponding to a first and a second extended portion of the object;  performing a line scan connecting the first and second circular scans to acquire a third set of cone beam projection data;  reconstructing an image of the ROI defined by the first and second extents by selectively combining a portion of the first set of acquired cone beam projection data corresponding to the ROI, a portion of the second set of acquired cone beam projection data corresponding to the ROI and the third set of cone beam projection data;  reconstructing an image of a first extended portion of the object that extends beyond the first extent of the ROI using the third set of cone beam projection data and a remaining portion of the first set of cone beam projection data that does not correspond to the ROI; and  reconstructing an image of a second extended portion of the object that extends beyond the second extent of the ROI using the third set of cone beam projection data and a remaining portion of the second set of cone beam projection data that does not correspond to the ROI. 10. The method of  claim 9 , further comprising the step of combining the reconstructed images of the ROI and first and second extended portions to obtain an image of an extended ROI. claim 9 11. The method of  claim 9 , wherein the steps of reconstructing the first and second extended portions comprise the steps of ramp filtering the corresponding cone beam projection data of the first and second circular scans and space variant filtering the third set of cone beam projection data. claim 9 12. The method of  claim 9 , wherein the step of reconstructing the ROI comprises augmenting missing Radon data from the first and second circular scans using the third set of cone beam projection data. claim 9