LAUSR

Rubidium-82 (Rb-82) and Thallium-201 (Tl-201) have similar activity to that of a potassium ion (K). Both tracers are active participants in the sodium– potassium exchange pump of cells. They are rapidly extracted from the blood and are taken up by the cells in relation to the tissue perfusion, which requires energy for cells uptake through Na/K-ATPase. This characteristic makes these tracers the gold standard in studying myocardial perfusion. As with Tl-201, Rb-82 has been reported in literature to have increased uptake in both benign and malignant neoplasms which were incidentally noted on Rb-82 PET myocardial perfusion studies. Increased Rb82 accumulation was reported in Spironolactone-induced gynecomastia, metastases from pheochromocytoma and metastatic breast cancer to the brain. Tl-201 has approved use in brain SPECT imaging to distinguish CNS lymphoma from toxoplasmosis in AIDS patients. There are no reports in the literature which describe the potential use of Rb-82 to differentiate inflammatory/infectious from neoplastic lesions. We present two case reports of pathologyproven neoplastic and inflammatory lesions incidentally noted on Rb-82 FDG PET myocardial perfusion-viability imaging studies with different Rb-82 and 18-F FDG activity. CASE PRESENTATION