¹⁸F-FDG PET before and after treatment in a patient with high-grade NHL relapsing 1 month after the¹⁸F-FDG PET study. On the left, ¹⁸F-FDG PET before treatment: multiple lymph node (cervical, axillary, mediastinal, hilar, iliac, and retroperitoneal) and splenic infiltration. On the right, ¹⁸F-FDG PET after treatment: residual¹⁸F-FDG uptake in hilar, retroperitoneal lymph nodes, and spleen. The CT scan indicated residual masses in the same areas as¹⁸F-FDG PET.