The mass of an object may be estimated based on intersection points of a representation of a surface in an image space with cubes defining the image space, the surface representing a surface of an object. The representation may be, for example, based on marching cubes. The mass may be estimated by estimating a mass contribution of a first set of cubes contained entirely within the representation of the surface, estimating a mass contribution of a second set of cubes having intersection points with the representation of the surface, and summing the estimated mass contribution of the first set of cubes and the estimated mass contribution of the second set of cubes. The object may be segmented from other portions of an image prior to estimating the mass of the object.