FIGURE 4.  (A) Transaxial CT image of 68-y-old woman with bladder lymphoma shows residual wall thickening after chemotherapy (arrows). (B and C) Transaxial ¹⁸F-FDG PET images of bladder before (B) and after (C) furosemide challenge show significant residual urinary activity and complete, postdiuretic, washout with no evidence of active tumor manifestation. True-negative postdiuretic PET finding was confirmed by clinical and radiologic follow-up.