1. A method for automatically extracting a bone structure from a medical image, comprising: using a processor to carry out the steps of: performing a thresholding on each voxel of the medical image in an intensity range of the bone structure to generate a first bit mask; eroding the first bit mask to remove connections between blood vessels and the bone structure to generate a second bit mask, wherein the connections are within the intensity range; performing a region growing within the second bit mask starting from a seed point by growing voxels into neighboring voxels within the intensity range to separate the bone structure from unconnected blood vessels and to generate a third bit mask; dilating the third bit mask to recover a surface area of the third bit mask to generate a fourth bit mask; and performing a region growing within the fourth bit mask starting from the seed point by growing into neighboring voxels within the intensity range to generate a fifth bit mask representing the bone structure.