Phase II study of Tc-99m MAG3 in patients with nephrourologic diseases.
Tc-99m-labeled mercaptoacetyltriglycine (Tc-99m MAG3) is a recently introduced radioagent that is excreted by tubular function. The aim of this study was to test Tc-99m MAG3 as an imaging agent for renal scintigraphy and renal plasma flow measurement. Image quality was tested with four different administered doses of Tc-99m MAG3, 100 MBq, 200 MBq, 300 MBq and 400 MBq, in four patients each. All administered doses except 100 MBq were sufficient for visible inspection of the nephrogram and drainage images; however, an administered dose higher than 300 MBq was necessary to maintain the quality of the blood perfusion image. The blood clearance with Tc-99m MAG3 or I-131 orthoiodohippurate (I-131 OIH) was calculated within the same day by the single blood sampling method. The blood clearance with Tc-99m MAG3 was 1.2-fold lower than with I-131 OIH, but correlated well (OIH = 91.34 +/- 0.932 MAG3, r = 0.953, P < 0.001). The blood clearance with Tc-99m MAG3 also correlated with the percentage of renal uptake estimated by the count-based gamma camera method at 1.5 to 2.5 minutes after injection (ERPF = -59.13% +/- 16.87% uptake, r = 0.845, P < 0.01). The mean labeling yield of Tc-99m MAG3 was 97%. None of the patients complained of side effects from Tc-99m MAG3. Tc-99m MAG3 is concluded to have good properties as a tubular radioagent for dynamic renal scintigraphy and renal plasma flow measurement.