Title :
Exact (spiral+circles) scan region-of-interest cone beam reconstruction via backprojection
Author :
Tam, K.C. ; Lauritsch, G. ; Sourbelle, K. ; Sauer, F. ; Ladendorf, B.
Author_Institution :
Siemens Corp. Res. Inc., Princeton, NJ, USA
fDate :
5/1/2000 12:00:00 AM
Abstract :
The authors present a (spiral + circles) scan cone beam reconstruction algorithm in which image reconstruction proceeds via backprojection in the object space. In principle, the algorithm can reconstruct sectional region-of-interest (ROI) in a long object. The approach is a generalization of the cone beam backprojection technique developed by Kudo and Saito (1994) in two aspects: the resource-demanding normalization step in the Kudo and Saito´s algorithm is eliminated through the technique of data combination that the authors published earlier, and the elimination of the restriction that the detector be big enough to capture the entire cone beam projection of the ROI. Restricting the projection data to the appropriate angular range required by data combination can be accomplished by a masking process. Because of the simplification resulting from the elimination of the normalization step, the most time-consuming operations of the algorithm can be approximated by the efficient step of line-by-line ramp filtering the cone beam image in the direction of the scan path, plus a correction image. The correction image, which can be computed exactly, is needed because data combination is not properly matched at the mask boundary when ramp filtering is involved. Empirical two-dimensional (2-D) point spread function (PSF) is developed to improve matching with the correction image which is computed with finite samplings. The use of transition region to further improve matching is introduced. The results of testing the algorithm on simulated phantoms are presented.
Keywords :
computerised tomography; image reconstruction; medical image processing; angular range; backprojection; correction image matching; data combination technique; empirical two-dimensional point spread function; exact scan region-of-interest cone beam reconstruction; line-by-line ramp filtering; long object; masking process; medical diagnostic imaging; resource-demanding normalization step; sectional region-of-interest; simplification; Computational modeling; Filtering algorithms; Image reconstruction; Image sampling; Imaging phantoms; Matched filters; Reconstruction algorithms; Spirals; Testing; Two dimensional displays; Algorithms; Humans; Image Processing, Computer-Assisted; Models, Theoretical; Phantoms, Imaging; Radon; Tomography, X-Ray Computed;
Journal_Title :
Medical Imaging, IEEE Transactions on