1. A method for segmenting the image of the heart using a three-dimensional (3-D) volume of images of a subject without the introduction of contrast material into the subject, the images containing imaging elements representative of physical properties of the body of the subject, the method comprising: acquiring a 3-D volume set of images containing voxels having representative properties of the body tissues; analyzing the set of images in a computer to identify voxels having intensities likely to represent blood and muscle; analyzing the identified voxels to determine which voxels satisfy preset criteria; rejecting voxels as not heart tissue if the preset criteria are not satisfied; and determining that the remaining voxels constitute heart tissue.