1. A computer-implemented method of generating a segmented image of an anatomical structure, the method comprising: a) providing, from a register to a mapping module, an initial boundary estimate of the anatomical structure; b) determining, by the mapping module, a boundary band region that includes the initial boundary estimate of the anatomical structure by sampling image data along a series of lines normal to the initial border estimate; c) converting the boundary band region to a rectangular boundary image and the boundary estimate to a curve within the rectangular boundary image such that the boundary estimate is defined relative to a coordinate grid of the rectangular boundary image; d) using a processor, (i) segmenting the boundary estimate within the rectangular boundary image and (ii) mapping the segmented boundary estimate from the rectangular boundary image onto the boundary band region to obtain a segmented boundary estimate; e) repeating steps b) through d) using the segmented boundary estimate from the rectangular boundary image as the initial boundary estimate within an updated boundary band, until the tolerance difference is below a threshold; and (f) generating, using the processor, an improved segmented image of the anatomical structure from the segmented boundary estimate.