关键词: CT成像, 锥束螺旋, 半覆盖扫描, PI线, Katsevich算法

Abstract: Helical cone-beam CT with half-cover scan can enlarge field-of-view of conventional helical cone-beam CT. Projections are transversely truncated at each view angle. Katsevich algorithm is an exact imaging algorithm, and can obtain good reconstruction image. This algorithm needs that data are not truncated on PI line. Therefore, conventional Katsevich algorithm is not directly used for half-cover scan. A non-PI line Katsevich algorithm is proposed according to the property of half-cover scan and analysis of conventional Katsevich algorithm. In the proposed algorithm, derivative of projection, not firstly rebinned in the Tam window, is directly filtered along row of planar detector. Backprojection interval is not PI interval, computed according to reconstruction point, but only 2π interval computed by z-coordinate. The result invalidates that the proposed algorithm avoids PI line and obtains complete image of inspected area.

Key words: Computed Tomography（CT） imaging, cone-beam helix, half-cover scan, PI line, Katsevich algorithm