tc-99m DMSA

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Tc-99m DMSA (2,3 dimercaptosuccinic acid) is a technetium radiopharmaceutical used in renal imaging to evaluate renal structure and morphology, particularly in pediatric imaging for detection of scarring and pyelonephritis. DMSA is an ideal agent for assessment of the renal cortex as it binds to the sulfhydryl groups in proximal tubules at the renal cortex with longer retention than other agents. This results in higher concentration and hence much higher resolution with pinhole SPECT. Also, it allows better assessment of differential renal function. It is a static scan as opposed to dynamic DTPA or MAG3 scans.

Characteristics

  • photon energy: 140 keV
  • physical half-life: 6 hours
  • biological half-life: 2.5-3.5 hours
  • 2.3 < pH < 3.5
  • normal distribution: kidneys (100%)
  • excretion: renal
  • target organ: kidneys
  • pharmacokinetics:
    • after the injection 90% of the 2,3 dimercaptosuccinic acid is bound to plasma proteins
    • 40-50% fixed to cortex (greater than glucoheptonate)
    • maximal cortical uptake within 3 hours
  • miscellaneous facts: 
    • high-resolution imaging with pinhole collimators and SPECT is not possible with DTPA, MAG3 or OIH because of rapid transit times
    • diseases affecting the proximal convoluted tubules such as renal tubular acidosis, Fanconi syndrome and nephrotoxic drugs such as gentamicin and cisplatin also inhibit the DMSA uptake

Uses, doses and timings

Renal cortical imaging
  • adult dose: 555 MBq (15-20 mCi) IV
  • pediatric dose : 1.85 MBq/kg (0.05 mCi/kg)
    • minimum 18.5 MBq (0.5 mCi)
  • image at 2 hours
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