EVALUATION OF TECHNETIUM-99M-ETHYLENEDICYSTEINE IN RENAL DISORDERS AND DETERMINATION OF EXTRACTION RATIO

This article evaluates the clinical usefulness of Tc-99m-ethylenedicys teine (EC) in patients with various renal disorders. In addition, extr action ratios of Tc-99m-EC in five volunteers Were also determined. Me thods: Twenty patients were intravenously injected with 200 MBq Tc-99m -EC and 2.5 MBq [(131)l]orthoiodohippurate (OIH) simultaneously and 11 blood samples were withdrawn within 60 min. Plasma clearance was dete rmined on the basis of a two-compartment model. Imaging was performed in the posterior projection by acquiring three sets of images. Extract ion ratios were determined from the blood samples obtained from the re nal vein and abdominal aorta Results: Renal clearance of Tc-99m-EC was significantly lower than that of OIH (p = 0.0003) with good correlati on (r = 0.93). Volume distributions of Tc-99m-EC and OIH were 26584 +/ - 10807 ml/1.73 m(2) and 23148 +/- 7602 ml/1.73 m(2), respectively (p = 0.047). The clearance half-lives of Tc-99m-EC and OIH were 98 +/- 54 min and 74 +/- 54 min, respectively (p = 0.049). Protein binding of T c-99m-EC (33 +/- 3.2% was significantly less than that of OIH (62 +/- 2.8%) (p < 0.0001). Red blood cell binding of Tc-99m-EC was almost neg ligible (5.7 +/- 4.3%). Similar extraction ratios were obtained from b lood (0.68 +/- 0.08) and plasma (0.70 +/- 0.07) (p = 0.062). The 60-mi n excretion fractions were similar for Tc-99m-EC and OIH, with Values of 50% +/- 20% and 51% +/- 19%, respectively (p = 0.9). Conclusion: Te chnetium-99m-EC is a suitable radio-pharmaceutical for routine renal d ynamic studies. Although the biological behavior of Tc-99m-EC seems to be different from that of OIH, their clearances demonstrate high corr elation. Technetium-99m-EC provides excellent quality images and has h igh potential in the evaluation of quantitative renal functions.