1. A method for electronically cleansing a virtual object, formed from acquired image data converted to a plurality of volume elements, each volume element having an intensity value, comprising: defining a partial volume image model for volume elements representing a plurality of material types based on the intensity value of the volume element; estimating a material mixture for volume elements representing a plurality of material types using the observed intensity values and the defined partial volume image model; classifying the volume elements representing a plurality of material types in accordance with the estimated material mixture; evaluating the volume elements in at least one classification; reclassifying incorrectly classified volume elements; grouping volume elements according to their material or material mixture into different regions; assigning the volume elements in each region as different parts of the virtual object; and removing at least one classification of volume elements when displaying the virtual object.