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 prepar ed in-house using an instant kit vial and I-123-OIH was commercially a vailable in a form already labelled. Both studies were undertaken in 2 0 patients with nephrourological disorders after intravenous (i.v.) in jection of 300 MBq Tc-99m-MAG3 and 34 MBq I-123-OIH within the time in terval of 3 to 4 days. Tc-99m-MAG3 was much superior to I-123-OIH in v isualization of renal perfusion, renal parenchyma and urinary tract. T he time parameters of the renogram, T(max), and TI/2 were significantl y 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-OI H but correlated well with that of I-123-OIH (r = 0.958, P < 0.01). Th e % renal uptake of Tc-99m-MAG3 per injected dose, which was calculate d by the gamma camera method, also correlated well with effective rena l 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, T c-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.