Tc-99m labeled RBC

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Tc-99m labeled RBC is one of the technetium radiopharmaceuticals used in the assessment of GI bleeding.

Characteristics

  • photon energy: 140 KeV
  • physical half-life: 6 hours
  • biological half-life: 
  • normal distribution: heart, vessels, spleen
  • miscellaneous facts:
    • threshold for detection is 0.05-0.1 mL/min
    • angiography threshold is 0.5-1 mL/min
    • criteria for positive scan: hot spot appears and conforms to intestinal anatomy, abnormal activity increases over time, activity moves antegrade or retrograde through bowel

Uses, doses and timings

  • GI bleeding
  • adult dose: 925 MBq (25 mCi) IV
  • timing: immediate (1 sec frames x 60 sec; 1 min frames x 60-90 min); delayed imaging if necessary