On perspective maximum intensity projection of CRA data

Three-dimensional (3D) computed rotational angiography (CRA) using an X-ray image intensifier based C-arm imaging system is a relatively new modality useful in cerebral angiography and neuro-interventional surgical procedures. In this paper, we present and study several algorithms for estimating the perspective maximum intensity projection (MIP) - PMIP - of CRA (neuro-angiographic) data. The nature of the data, intended applications and the associated approximations differ from those in spiral CT and MR angiography (in which parallel MIP is used extensively). Of relevance is perspective geometry, the intrinsic parameters associated with which are those of the C-arm imaging system. Its relatively small X-ray cone-angle makes the voxel driven method viable for certain applications. Consequently, the voxel-driven method is considered in greater detail. Sparseness of neuro-angiographic data allows thresholding, and hence acceleration. This feature is useful for a rapid preview and as an aid to 2D/3D registration. Post-processing for improving the quality of voxel-driven PMIP is discussed, and an adaptive algorithm is proposed in the context. Results of PMIP of data acquired by scanning patients with a prototype C-arm system are presented.