1. A method for estimating a mass of an object, said method comprising: acquiring image data including a plurality of image elements; calculating a histogram based on the image data; calculating a computed tomography (CT) number of the object using an anisotropic erosion operator; determining a perimeter of the object; calculating an estimated mass of the object using the CT number and a first subset of image elements of the plurality of image elements, the first subset of image elements defined by the perimeter of the object; and outputting at least one of the estimated mass of the object and an image including the object.