in a method and apparatus for detecting and displaying arbitrary interior surfaces of a three - dimensional body from a regular array of values of at least one physical property in the interior of the body , the physical property measurements are made with systems such as computerized tomographic x - ray imaging , or magnetic resonance imaging . a recursive algorithm starts with a seed voxel in the surface of interest and continues to all adjacent voxels having a common face which is penetrated by the surface of interest . the common surface penetrations are derived from a look - up table which lists the adjacent voxels having a common penetrated face for each voxel index . the voxel index , in turn , is the string of binary digits representing the voxel vertices whose vertex values exceed the surface value of the surface of interest . the resulting list of voxels can be processed by conventional processors to display the surface of interest with greatly reduced interference from nearby , closely intermingled surfaces with the same or similar surface values .