Disparities in uptake pattern of (123)I-MIBG, (18)F-FDG, and (99m)Tc-MDP within the same primary neuroblastoma.

We report an unusual case of primary neuroblastoma in an 11-year-old girl. The superior portion of the tumor accumulated I-MIBG, Tc-MDP, and F-FDG. In contrast, the inferior portion of the tumor showed no abnormal F-FDG or Tc-MDP uptake, which usually indicates tumor necrosis. This inferior portion of the tumor, however, had intense I-MIBG activity, consistent with viable tumor rather than tumor necrosis.

In vitro effect of cyclophosphamide on the binding of radiopharmaceuticals (99mTcO4- and 99mTc-MDP) to blood elements.

Sodium pertechnetate (99mTcO4-) and many 99mTc-products are the radiopharmaceuticals most frequently used in nuclear medicine. Using an in vitro model, we evaluated the effect of cyclophosphamide on percent radioactivity of 99mTcO4- and methylenediphosphonic acid (99mTc-MDP) bound to isolated blood elements. Blood samples were incubated with the two radiopharmaceuticals, plasma and blood cells were separated and precipitated, and soluble and insoluble fractions were separated. To evaluate the effect of cyclophosphamide, blood was incubated with this drug 1 h prior to the addition of the radiopharmaceuticals. The fraction of 99mTcO4- radioactivity was slightly higher in plasma (61.2 to 53.8%) than in blood cells (38.8 to 46.2%) up to 6 h and cyclophosphamide did not interfere with this distribution. The amount of 99mTc-MDP radioactivity was higher in plasma (91.1 to 87.2%) than in blood cells (8.9 to 12.8%) up to 24 h and cyclophosphamide did not modify it. The binding of 99mTcO4- to the insoluble fraction of plasma (4.9 to 6.1%) was low and cyclophosphamide did not interfere with it up to 6 h, but a small blockade (9.8 to 4.8%) was observed at 24 h. From 3 h on, cyclophosphamide slightly inhibited 99mTcO4- binding to blood cells (23.1 to 16.6%) and increased it at 24 h (31.2 to 14.3%). Cyclophosphamide did not alter 99mTc-MDP binding to the insoluble fraction of blood cells and slightly decreased 99mTc-MDP binding to the insoluble fraction of plasma (29.8 to 23.6%) up to 6 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cyclophosphamide on the binding of 99mTcO-4 and 99mTc-MDP to blood cells and plasma proteins.

Since the introduction of technetium-99m (99mTc) and its rapid acceptance as a tool in nuclear medicine, very little information is available about its biological action as 99mTc-radiopharmaceuticals. We have determined if cyclophosphamide, an alkylating agent, used in oncology as a chemotherapeutic drug, modifies the binding of 99mTcO-4 and 99mTc-MDP (99mTc-methylenediphosphonic acid) to blood cells and to plasma proteins. The radiopharmaceuticals were injected intravenously (iv) into SW-55 mice (male and female, weight 25 g) and samples of plasma and blood cells were separated. Cyclophosphamide (50 micrograms) was injected iv 1 h before the radiopharmaceuticals. Samples of plasma and blood cells were also precipitated with 5% trichloroacetic acid and soluble and insoluble fractions were isolated. The following results were obtained: 1) cyclophosphamide did not alter (0.25 to 8 h) percent radioactivity of 99mTcO-4 in plasma or blood cells but increased the binding of 99mTc-MDP to blood cells; 2) cyclophosphamide did not alter (0.25 to 8 h) the binding of 99mTcO-4 in insoluble fraction of plasma and decreased (1 to 4 h) percent radioactivity of 99mTc-MDP in the insoluble fraction of plasma; 3) cyclophosphamide increased (0.25 to 4 h) percent radioactivity of 99mTcO-4 in the insoluble fraction of blood cells but did not alter the binding of 99mTc-MDP. Cyclophosphamide and/or its metabolites modified the effective half-life of these radiopharmaceuticals (to 99mTcO-4 was increased 2.3 to 3.4 h and to 99mTc-MDP was decreased 3.3 to 2.1 h) and possibly increased the permeability of blood cells to 99mTcO-4.