tc-99m MAG3

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Tc-99m MAG3 (mercaptoacetyltriglycine) is one of the technetium radiopharmaceuticals used in renal imaging. Due to favorable energy and dosimetric characteristics, MAG3 radiolabeled with technetium has replaced the iodide-131 Hippuran for the study of renal function (tubular secretion physiology) .

Characteristics

  • photon energy: 140 KeV
  • physical half-life: 6 hours
  • biological half-life: 4 hours
  • technetium oxidation state: +5
  • normal distribution: kidneys (100%)
  • pharmacokinetics:
    • uptake by tubular secretion (97%)
    • first pass filtration 60%
  • excretion: renal via both glomerular filtration and tubular excretion; hence, in pediatric patients and patients with poor renal function this test is considered superior to DTPA scan
  • target organ: bladder
  • miscellaneous facts
    • good quality images with renal insufficiency
    • by giving captopril, MAG3 plasma clearance decreases in hypertensive patients with renal artery stenosis but increases in patients without renal artery stenosis
    • cannot measure GFR as it is cleared almost entirely by tubular secretion

Uses, doses and timings

  • renal study
    • adult dose: 296 MBq (8 mCi) IV
    • pediatric dose: 3.7 MBq/kg (0.10 mCi/kg) (minimum: 14.8 MBq (0.4 mCi))
    • 60-sec flow study; then every 5 min for 25 min
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