Removal of Partial Volume Effected Voxels

As I had pointed out earlier in previous posts, perhaps the one and only reason the segmentation algorithm leaks into surrounding structures especially the aorta and the pulmonary artery is because of partial volume effected voxels. We have observed that the segmentation at times will leak into the pulmonary artery through a pulmonary vein. Although, it is physically possible, atleast in theory, for the pulmonary vein to touch the pulmonary artery. However, our images are Angiographic scans where the blood was Gadolinium-enhanced and the only thing that we see after subtracting the pre-Angio from the post-Angio is the blood pool. So, we can rightfully state that the blood pools of the pulmonary artery and the pulmonary vein cannot physically touch and this is definitely caused by partial volume effected voxels. Partial volume effected voxels are voxels that image two or more tissue types, thus giving an intensity level that is a weighted average of the intensity levels of each tissue type.

So here arises a dire requirement to identify partial volume effected voxels and remove them as much as possible. I have been looking at some papers recently such as Ballester et. al., and my task for this week will mainly be literature review of partial volume effect removal techniques.