Low-dose MAG3 renogram in adult and paediatric patients - How low can we go?

Abstract

A MAG3 (mercaptoacetyltriglycine) renogram is a commonly performed nuclear medicine study that visually and functionally evaluates renal blood supply and glomerular filtration. After injection of 99mTc‐MAG3, multiple images are taken over 30 minutes. Both qualitative and quantitative data is produced to compare asymmetrical and overall renal function. The radiotracer imparts ionising radiation to the patient. By limiting the dose of radiotracer used, the amount of radiation could be lowered, however this often comes at the tradeoff of a lower quality study. Our aim is to determine how far the radiotracer 99mTc‐MAG3 dose can be reduced while maintaining a diagnostic quality study in both adult and paediatric cohorts.

Methods Approved by the Gold Coast University Hospital Human Research Ethics Committee. Nine adults (age 19‐66) and six paediatric patients (age 0‐9) with a routine clinical renogram at Gold Coast University Hospital between April to July 2017 were retrospectively and selectively chosen to allow an even distribution of weight. Poisson resampling of acquired counts was applied to simulate MAG3 renogram scans at varying radiotracer doses (100%, 75%, 50% and 25%). These 60 reconstructed studies were deidentified and randomised to order, then reviewed by a blinded final year radiology registrar and nuclear medicine consultant and categorised as either excellent, satisfactory or suboptimal.

Results Five cases (33%) showed a drop in readability at lower radiotracer levels, and only one of these (6%) reduced quality from satisfactory to non‐diagnostic. There was no statistically significant difference in readability variation between adult and paediatric patients, however paediatric patients were more likely (50% vs 11% in adults) to have a non‐diagnostic study.

Conclusion Renogram 99mTc‐MAG3 dose can be significantly reduced while maintaining a diagnostic‐quality study in both adult and paediatric populations.