Systems and methods for segmenting a medical image are provided. In some embodiments, the method includes receiving an image acquired from at least a portion of a subject's anatomy, selecting a first point within a target structure identified on the image, and determining a second and a third point associated with extents of a target biological tissue, the first, second and third points defining a sector described by the first point, a central angle and a subtended arc. The method also includes determining a plurality of arc points along the subtended arc, and extending a plurality of linear segments along directions determined by the first point and the plurality of arc points. The method further includes determining an intensity profile along each linear segment to identify boundaries of the target biological tissue, and generating a contour of the target biological tissue using the identified boundaries.