1. An image data processor, comprising: a shape likelihood determiner comprising a processor configured to process voxels of image data and determine a likelihood that a voxel represents predetermined tissue of interest for a plurality of the voxels based on a shape of a tissue represented by the voxel, wherein the likelihood for the voxel is a value from zero to one; an opacity determiner comprising the processor, which is further configured to determine an opacity suppression for each of the plurality of voxels based on the likelihood; a re-formatter comprising the processor, which is further configured to re-format the image data based on the determined opacity suppression, generating opacity suppressed re-formatted data, wherein a voxel with a likelihood of zero of representing tissue having the shape is not suppressed, a voxel with a likelihood of one of representing tissue having the shape is fully suppressed such that it is not visible in the image data, and a voxel with a likelihood between zero and one is partially suppressed, with a degree of suppression based on the likelihood; and a rendering engine comprising the processor, which is further configured to visually presents the opacity suppressed re-formatted data, wherein the tissue of interest is not opacity suppressed in the visually presented re-formatted image data, and a second tissue other than the tissue of interest is gradually visually opacity suppressed with suppression increasing from a center of the second tissue to an outer periphery of the second tissue.