1. A method for detecting a nodule, or other shaped target, in image data, the method comprising steps of: segmenting scanning information from an image slice to isolate lung tissue from other structures, resulting in segmented image data; extracting anatomic structures, including any potential nodules, from the segmented image data, resulting in extracted image data; and detecting possible nodules, or other shaped targets, from the extracted image data, based on deformable prototypes of candidates generated by a level set method in combination with a marginal gray level distribution method, wherein detecting possible nodules, or other shaped targets, includes: generating a deformable prototype by applying the level set method to the extracted image data; assigning gray levels to the deformable prototype using the marginal gray level distribution method; and determining similarity between gray levels in the extracted image data and the deformable prototype.