Fig. 3

Transaxial ¹⁸F-FDG PET/CT (a) and ¹⁸F-FLT PET/CT (b) images at the pelvic level of a 65-year-old male patient with initial diagnosis of MM. Focally increased ¹⁸F-FDG accumulation (arrow, a) in the left iliac bone, reflecting an active MM lesion (SUV_mean = 5.1, SUV_max = 7.2). ¹⁸F-FLT PET/CT also demonstrates focally enhanced tracer accumulation in the same anatomical site (arrow, b), higher than the normal bone marrow uptake (SUV_mean = 14.1, SUV_max = 16.8). Notice the physiologically increased ¹⁸F-FLT bone marrow uptake rendering evaluation of skeletal lesions challenging (reference SUV_mean = 6.5, SUV_max = 10.2)