4-Scanning
Scanning can also involve determining the actual physical or chemical makeup of a substance, something that Acoustic Microscopy doesn't do. For that type of scanning you would use Acoustic Spectroscopy. The first two examples are in The Three Doctors when the Third Doctor scanned a field, and later his sink, for traces of antimatter. he wasn't scanning an actual object, only the traces left over. The best know biological scanning was in The Empty Child/The Doctor Dances when the Ninth Doctor scanned the hospital patients to determine whether the gas masks were actually a part of them. In The Lazarus Experiment The Tenth Doctor scanned the area for Lazarus' DNA signature which enabled him to pick up traces of DNA and hone in on where Professor Lazarus was. The Eleventh Doctor, on the other hand, scans everything... This is a more analytic type of scanning called Acoustic Spectroscopy that in today's science is limited to the properties of fluids and dispersed particles. But as with all sciences, advances could someday make it possible to analyze solid objects or even gases. It works by determining the particle size, and distribution of those particles which enables it to identify the material(s) that compose an object. With time, this science could be expanded to reveal the object's entire chemical and physical nature.