Comparison of Gallium-67 and Tc-99m Tetrofosmin uptake in lymphoma

Full text: Radionuclide imaging of lymphomas with 67Ga is a well established procedure. Other agents employed include 18FDG and 201Tl Chloride. However 67Ga, 18F and 201Tl are all cyclotrons produced radionuclides and not readily available in India. Assuming similarity of behaviour with 201Tl Chloride newer technetium labelled myocardial perfusion agents have been studied in imaging the tumors. We used 99mTc-tetrofosmin (Myoview, Amersham International UK) for imaging of lymphoma patients. Uptake of tetrofosmin is thought to be associated with mitochondria and any inhibition of mitochondria inhibits the uptake of 99mTc tetrofosmin. Most of the sub-cellular activity is found in cytosolic fraction but not bound to cytosolic protein. The retention is probably due to ionic reaction between positively charged tetrofosmin and negatively charged cytosol. Radionuclide scanning with 67Ga is commonly positive in intermediate and high grades lymphomas. However, it has low sensitivity in differentiated lymphoma. It is also useful in assessing the response to treatment and relapses. 67Ga SPECT is very sensitive in detecting tumor infiltration. The accumulation of 67Ga into the cell is via transport of iron binding protein (lactoferrin). 67Ga is not taken up by necrotic or quiescent cells but by proliferating malignant cells. In this study 13 patients of lymphoma (Hodgkin's and Non-Hodgkin's) in different stages of disease were evaluated. Both dynamic and static studies were performed. Dynamic study was examined for vascularity of the lesions and static scans for intensity of uptake. Tc-99m Tetrofosmin was given intravenously and static images of the involved site were acquired at 10 minutes and 30 minutes. Static images of the skull, chest, axillae, abdomen and pelvis were acquired at 30 minutes. The total numbers of clinically involved sites were 75 and Tetrofosmin uptake was seen in 16 (20%) sites. 5 patients initially studied with Tetrofosmin were later on studied with Gallium 67 also. About 4-5 mCi of gallium-67 was given intravenously and imaging done after 72 to 96 hours. Whole body profile was acquired and spot views of involved sites were also acquired. The number of sites showing uptake with Gallium 67 and Tetrofosmin were compared. There were 25 clinically involved sites in 5 patients. The total number of sites showing Gallium 67 uptake were 11(44%) and total number of sites showing Tetrofosmin uptake were only 8(32%). The problems faced in imaging with Tetrofosmin were (i) uptake in abdominal sites was hampered by immediate hepatobiliary excretion (ii) salivary gland secretion interfered with cervical nodal imaging (iii) extra nodal sites especially liver and spleen were not clearly delineated. We conclude that Gallium 67 is superior to tetrofosmin in imaging lymphoma. (author)