The division of the MR imaging environment into four distinct, clearly labeled zones—with progressive restriction of entry and increased supervision for higher zones—is a mandatory and
key aspect in avoidance of MR imaging–related accidents. The zones are labeled I–IV, with zoneI being the least restricted and zone IV being the most restricted. Access is progressive—for example, a person with zone III access automatically has access to zones I and II. The four zones
are defined as follows: