Introduction: L,L-ethylenedicysteine (EC) is a new carrier of technetium Tc 99m (99mTc) with a lower affinity to plasma albumin in comparison with diethylenetriamine pentaacetic acid (DTPA). We compared 99mTc-EC scan with 99mTc-DTPA scan in diuretic renography for patients with obstructive uropathy.
Materials and methods: Thirty-three patients with upper urinary tract obstruction were randomly selected and underwent diuretic renographies by 99mTc-EC and 99mTc-DTPA. The counts of radioisotope per pixel in the target (the kidney) and background tissues as well as the clearance half-life of these two radiopharmaceuticals were measured and compared.
Results: Mean counts of radioisotope per pixel in the target tissue was not different between 99mTc-EC and 99mTc-DTPA scans, but in the background tissue, it was less for 99mTc-EC (P = .003). Target-background ratio was higher for 99mTc-EC scan (3.80 +/- 2.11 versus 2.48 +/- 1.39; P < .001). Renal clearance half-life of radioisotope was shorter for 99mTc-EC scan than 99mTc-DTPA scan (58.15 +/- 15.17 minutes versus 78.65 +/- 19.99 minutes; P = .033). The results were similar for uremic patients (with a serum creatinine level > 2mg/dL).
Conclusion: Target-background ratio of radiopharmaceutical uptake rates in diuretic renography was a good indicator of the higher resolution of 99mTc-EC than 99mTc-DTPA scan. We also demonstrated the faster clearance of 99mTc-EC than 99mTc-DTPA. This results in less radiation that is especially useful in children. To our opinion, 99mTc-EC can better depict the kidneys in comparison with 99mTc-DTPA.