Figure 1. Categories of signal enhancement. C1, no significant enhancement other than that shown by normal breast tissue over the course of the dynamic examination; C2, slowly and continously increasing signal intensity; C3, strong initial signal increase by at least 90% in the first or second minute followed by a further slow signal increase; C4, strong initial signal increase by at least 90% in the first or second minute followed by a plateau phenomenon (signal steady state); C5, strong initial signal increase by at least 90% in the first or second minute followed by a washout phenomenon (signal decrease).