Technetium-99m-N,N-Ethylenedicysteine--A Comparative Study of Renal Scintigraphy with Technetium-99m-MAG3 and Iodine-131-OIH in Patients with Obstructive Renal Disease

Technetium-99m-labeled N,N-ethylenedicysteine (99mTc-EC) is a new renal imaging agent introduced as an alternative for 99mTc-labeled mercaptoacetyltriglycine (99mTc-MAG3), with similar renal excretion characteristics. To evaluate the diagnostic characteristics of this agent, a gamma camera study was performed. Sixteen patients with obstructive renal disease and six normal controls were injected with 90 to 110 MBq of 99mTc-EC and 7.4 MBq 131I-labeled orthoiodohippurate (OIH). Serial images were obtained during 20 min for 99mTc-EC and 30 min for OIH. The study was repeated using 90 to 110 MBq 99mTc-MAG3 during the same week. Renograms, functional ratios and urinary excretion patterns of all three agents were similar. The mean time to peak activity values for OIH, 99mTc-EC and 99mTc-MAG3 were 4.25 +/- 0.37 min, 4.39 +/- 0.32 min and 4.00 +/- 0.24 min, respectively. The time from peak to 50% activity values for OIH, 99mTc-EC and 99mTc-MAG3 were 5.48 +/- 0.80 min, 6.93 +/- 0.69 min and 7.33 +/- 0.85 min, respectively. It is concluded that 99mTc-EC has excellent imaging characteristics and similar excretion properties to OIH. The advantages of 99mTc-EC over 99mTc-MAG3 are lower hepatobiliary uptake and simplicity of preparation.