COMBINED IN 111-DTPA AND TC-99M-MAG-3 REN AL SCINTIGRAPHY IN PEDIATRIC-PATIENTS

Renal scintigraphy after simultaneous injection of 125 muCi/kg Tc 99m MAG 3 and 25 muCi/kg In 111 DTPA was evaluated in 34 pediatric patient s undergoing investigations for urinary collecting system defects. Mea n age was 24 months (15 days to 14 years) ; 8 patients were younger th an one month. Double isotope acquisition was performed with one image every 15 seconds for 30 minutes. Furosemide was routinely injected aft er 20 minutes. Relative renal clearances and target-to-background rati o were determined and regions of interest were outlined on the renogra m. The furosemide effect was evaluated using a washout index comparing activities after 20 and 30 minutes. These parameters were determined for both tracers for the same regions of interest after normalization for the amount of radioactivity injected. Relative clearances were sim ilar with both tracers. Renogram amplitude and the target-to-backgroun d ratio were significantly higher with MAG 3 (p < 0.0001); the increas e in target-to-background ratio was less marked in younger patients an d for the right kidney (p < 0.002). The furosemide effect was greater by 15 % with MAG 3 (p < 0.0001). Thus, MAG 3 provided better data than DTPA, although it slightly underestimated function of the right kidne y as a result of liver uptake.