The n-PI-method for helical cone-beam CT

A new class of acquisition schemes for helical cone-beam computed tomograph y (CB-CT) scanning is introduced, and their effect on the reconstruction me thods is analyzed. These acquisition schemes are based on a new detector sh ape that is bounded by the helix. It will be shown that the data acquired w ith these schemes are compatible with exact reconstruction methods, and the adaptation of exact reconstruction algorithms to the new acquisition geome try is described. At the same time, the so-called PI-sufficiency condition is fulfilled, Moreover, a good fit to the acquisition requirements of the v arious medical applications of cone-beam CT is achieved. In contrast to oth er helical cone-beam acquisition and reconstruction methods, the n-PI-metho d introduced in this publication allows for variable pitches of the acquisi tion helix. This additional feature will introduce a higher flexibility int o the acquisition protocols of future medical cone-beam scanners. An approx imative n-PI-filtered backprojection (n-PI-FBP) reconstruction method is pr esented and verified. It yields convincing image quality.