Scintigraphy performed with Tc-99m labeled RBCs

Last revised by Francesco Sciacca on 8 Jan 2023

Tc-99m labeled RBCs - with radiolabelling technique in vivo or in vitro of red cells 3 - is one of the technetium radiopharmaceuticals used in the non-invasive assessment of gastrointestinal (GI) bleeding 2, characterized by high sensitivity (93%) and specificity (95%) 4. It is capable, in fact, of targeting intestinal hemorrhages of a few milliliters immediately after the injection of the radioactive tracer or in the following 12-24 hours (diluition principle) 5,6.


  • 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

    • the criteria for positive scan are qualitative type: 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/angioscintigraphic phase (1 sec frames x 60 sec); 1 min frames x 60-90 min; delayed imaging if necessary (6-8-24 hrs).

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Cases and figures

  • Case 1: splenosis
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  • Case 3: splenosis
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