FIG 5. Two-parameter scatter diagram showing amplitude (A) plotted against the distribution time (Tc). The recurrent IP (diamonds) are localized in the left upper corner, displaying a combination of high amplitude and short distribution time. Tumor recurrence can be defined by a combination of amplitude greater than 1.6 arbitrary units and distribution time less than 65 seconds. The postoperative changes (solid bullets) are characterized by low amplitude (<1.6 arbitrary units) and long distribution time (>65 seconds). Only one postoperatively changed lesion displayed high amplitude. In this case, the lesion still can be distinguished from a recurrent tumor on the basis of distribution time; however, if only the amplitude were considered, the lesion would be misclassified as a tumor