COMPARATIVE-STUDY OF RENAL SCINTIGRAPHY WITH (99)TCM-MERCAPTOACETYLTRIGLYCINE AND I-123 ORTHOIODOHIPPURATE

This study was undertaken to compare image quality, renal handling and plasma clearance of Tc-99-mercaptoacetyltriglycine (Tc-99m-MAG3) with those of I-123-orthoiodohippurate (I-123-OIH). Tc-99m-MAG3 was prepared in-house using an instant kit vial and I-123-OIH was commercially available in a form already labelled. Both studies were undertaken in 20 patients with nephrourological disorders after intravenous (i.v.) injection of 300 MBq Tc-99m-MAG3 and 34 MBq I-123-OIH within the time interval of 3 to 4 days. Tc-99m-MAG3 was much superior to I-123-OIH in visualization of renal perfusion, renal parenchyma and urinary tract. The time parameters of the renogram, T(max), and TI/2 were significantly prolonged in Tc-99m-MAG3 compared to those for I-123-OIH (P < 0.05). Plasma clearance of Tc-99m-MAG3 was also slower than that of I-123-OIH but correlated well with that of I-123-OIH (r = 0.958, P < 0.01). The % renal uptake of Tc-99m-MAG3 per injected dose, which was calculated by the gamma camera method, also correlated well with effective renal plasma flow (ERPF) calculated by the single blood sampling method (r = 0.940, P < 0.01). The renal handling and plasma clearance of Tc-99m-MAG3 are not completely identical with those of I-123-OIH. However, Tc-99m-MAG3 has the clinical advantages of superior image quality, the feasibility of gamma camera measurement of quantitative renal uptake, and ready availability for routine clinical use.