Figure 9a. Partial volume averaging effect. (a, b) Coronary catheter angiograms show wall irregularity of the LAD artery (arrowheads) without significant stenosis. (c, d) On thin-slab MIP (c) and curved MPR (d) images, the patency of the vessel lumen in the coronary arteries is difficult to appreciate due to diffuse and dense calcification. This blooming effect can lead to the creation of nonassessable segments or to pseudostenosis, depending on interpretation.