FIGURE 3. A 55-y-old man with NHL (diffuse large cell) underwent ¹⁸F-FDG PET using dual-head gamma camera with attenuation correction (MCD-AC; ADAC Laboratories, Milpitas, CA) before, after first cycle of, and at completion of chemotherapy. Pretherapy ¹⁸F-FDG PET image reveals extensive radiotracer uptake in anterior mediastinum. Note physiologic uptake in supraclavicular cervical muscles. Patient underwent chemotherapy with cyclophosphamide, hydroxydaunomycin, vincristine sulfate, and prednisone. After first cycle, residual disease was seen in anterior mediastinum (not shown). ¹⁸F-FDG PET image after last cycle (middle image) demonstrates no residual mass in mediastinum, consistent with complete resolution of disease. ¹⁸F-FDG PET image 8 mo after completion of therapy, however, reveals recurrence of disease in anterior mediastinum. Note physiologic uptake in heart in all images.