I understand that normal MRIs use a "coil" which is wrapped around the body and the machine scans only the area where the coil is located and the area is only about 12-16 inches or so in width. So, for example, if the spine needs to be MRI'ed then it is done in several segments, thoracic, lumbar, etc.
However, it seems that some MRI centers offer "full body MRI" that can scan the entire body in one step.
What is the difference between these processes? Is the same type of machine used for both?