1. A method of extracting vessel geometry from one or more scan images, comprising: determining a scale for a voxel in the one or more scan images; determining an orientation of the voxel; applying a matched filter using the scale and orientation to generate a filter response; determining, based on the filter response, whether the voxel represents a centerline of a vessel; repeating the above acts to identify a plurality of centerline voxels; and linking the plurality of centerline voxels together, wherein the linking comprises selecting a second voxel to link to a first voxel based on a likelihood that the second voxel is adjacent to the first voxel and part of the same vessel, wherein the likelihood is calculated by: determining a distance between the first voxel and other voxels; determining a difference between the orientation of the first voxel and other voxels; and determining a difference between the filter response of the first voxel and other voxels.