Tc-99m MAG3

Last revised by Raymond Chieng on 20 Dec 2022

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) 7.

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

    • during labeling , MAG3 is heated to remove S-benzoyl group. The S-benzoyl group is important to maintain the stability of the compound during storage conditions 8.

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)) 5

    • 60-sec flow study; then every 5 min for 25 min

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Cases and figures

  • Case 1: normal MAG3 study
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  • Case 2: normal
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  • Case 3: pelviureteric junction (PUJ) obstruction
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  • Case 3: left pelviureteric obstruction
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  • Case 4: normal captopril renal MAG3 nuclear study
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  • Case 5: renal artery stenosis
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