FIGURE 4.  Composite ROC curves of the 3 observers. A_z values for CT, ¹⁸F-FET PET, and ¹⁸F-FDG PET were 0.82, 0.93, and 0.95, respectively. Accuracy of observers did not significantly differ (P = 0.71) between ¹⁸F-FDG and ¹⁸F-FET PET but, in the distinction of carcinomas, was significantly (P < 0.05) greater with either technique than with CT.