A FAST MAXIMUM-INTENSITY PROJECTION ALGORITHM FOR GENERATING MAGNETIC-RESONANCE ANGIOGRAMS

Maximum-intensity projection (MIP) algorithms are one class of algorit hms currently used for construction of magnetic resonance (MR) angiogr ams. The blood flow in a volume of interest is represented by bright i ntensities in the MR data volume. MIP algorithms search for the maximu m intensity along parallel rays cast through the MR image volume. A pr ojection image is formed from these maximum intensity values. Thus, th e flow within the vasculature shows up in the projection plane. This r esearch strives to discover methods of reducing the time required to p roduce the projections, thereby making the technology more accessible to users of less powerful systems. A novel approach was developed for calculating projections in which each image slice was presorted into b ins of intensities. By relating the intensities of the pixels to their location in the slice, the total number of pixels considered for the projection plane was reduced, thus saving calculation time. Only those brighter intensities that relate to flow are used in the projection. Additional time savings resulted from precalculating projection ''temp lates'' and filling multiple projection planes at the same time. The a lgorithm was written in C on a 80386-based system. The new algorithm d emonstrated over a six-fold increase in projection calculation speed o ver a benchmark algorithm.