Various improvements may lead to reducing or avoiding artifacts in curved planar reformation imaging. The source of voxels used in projection rendering may be verified to be from the vessels rather than intervening anatomy. To make the check more rapid, a hierarchal data structure may be used. Rather than using the vessels, geometric forms fit to the vessels may be used. Processing with geometric forms may be more rapid than a fine mesh or surface. Since tubular structures have a predictable change over length, the geometric forms or the vessel data itself may be filtered with a monotonicity constraint. Instead of using planes for segments based on the lumen or center line, a convex hull around the tubular structures is formed for the curved planar reformation.