ISOCS can be very useful, but, yes, you need to have an experienced operator. ISOCS relies on "modeling" of the object to be shot, i.e. the material, its thickness, its density, dimentions, addtional layers of shielding, etc. The more known about the object, contents, etc., the better the results. If little is known about the object, the results can still be useful, but the accuracy may not be what you are wanting. Its all in the modeling.