1. A method for detecting pulmonary embolisms in computed tomographic (CT) angiography using a processor, said method comprising the steps of: providing a digitized CT image acquired from the inside of a pulmonary vessel, said image comprising a plurality of intensities corresponding to a 3-dimensional grid comprising a first plurality of voxels; for each of the first plurality of voxels in said image, extracting a first pulmonary embolism (PE) candidate and first PE boundary; and for each of a second plurality of voxels within said first PE boundary, selecting a voxel of the second plurality of voxels; extracting a subsequent PE candidate and subsequent PE boundary from said selected voxel; merging said subsequent PE candidate with said first PE candidate; and merging said subsequent PE boundary with said first PE boundary; wherein extracting a first or second pulmonary embolism (PE) candidate and first or second PE boundary from each of a first or second plurality of voxels, respectively comprises: tobogganing said voxel to a first concentration voxel: initializing a cluster with said first concentration voxel, and assigning to an active list all neighboring voxels whose intensity is indicative of being part of an embolism; removing a voxel with a minimal intensity from said active list; tobogganing said removed voxel to a second concentration voxel, wherein if said second concentration voxel is part of said cluster, assigning neighbors of said removed voxel to said active list, otherwise assigning said removed voxel to a boundary of said cluster; and repeating said steps of removing a voxel from said active list and tobogganing said removed voxel to a second concentration voxel until said active list is empty, wherein said cluster is the pulmonary embolism candidate; and wherein each of the foregoing steps is performed using a processor.