Reduction in Radiation Dose in Mercaptoacetyltriglycerine Renography with Enhanced Planar Processing

PURPOSE: To determine the minimum dose of technetium 99m ((99m)Tc) mercaptoacetyltriglycerine (MAG3) needed to perform dynamic renal scintigraphy in the pediatric population without loss of diagnostic quality or accurate quantification of renal function and to investigate whether adaptive noise reduction could help further reduce the minimum dose required. MATERIALS AND METHODS: Approval for this retrospective study was obtained from the institutional review board, with waiver of informed consent. A retrospective review was conducted in 33 pediatric patients consecutively referred for a (99m)Tc-MAG3 study. In each patient, a 20-minute dynamic study was performed after administration of 7.4 MBq/kg. Binomial subsampling was used to simulate studies performed with 50%, 30%, 20%, and 10% of the administered dose. Four nuclear medicine physicians independently reviewed the original and subsampled images, with and without noise reduction, for image quality. Two observers independently performed a quantitative analysis of renal function. Subjective rater confidence was analyzed by using a logistic regression model, and the quantitative analysis was performed by using the paired Student t test. RESULTS: Reducing the administered dose to 30% did not substantially affect image quality, with or without noise reduction. When the dose was reduced to 20%, there was a slight but significant decrease (P = .0074) in image quality, which resolved with noise reduction. Reducing the dose to 10% caused a decrease in image quality (P = .0003) that was not corrected with noise reduction. However, the dose could be reduced to 10% without a substantial change in the quantitative evaluation of renal function independent of the application of noise reduction. CONCLUSION: Decreasing the dose of (99m)Tc-MAG3 from 7.4 to 2.2 MBq/kg did not compromise image quality. With noise reduction, the dose can be reduced to 1.5 MBq/kg without subjective loss in image quality. The quantitative evaluation of renal function was not substantially altered, even with a theoretical dose as low as 0.74 MBq/kg.