What is the normal biodistribution of Tc sulfur colloid when administered intravenously?

• A. Liver 85%, spleen 10%, bone marrow 5%
• B. Liver 70%, spleen 15%, bone marrow 10%
• C. Liver 60%, spleen 20%, bone marrow 15%
• D. Liver 90%, spleen 5%, bone marrow 3%

Answer: (A)

The normal biodistribution of Tc sulfur colloid when administered intravenously typically shows a significant uptake in the liver, spleen, and to a lesser extent, bone marrow. The correct answer indicates a distribution of approximately 85% liver, 10% spleen, and 5% bone marrow. This aligns with the expected behavior of sulfur colloid, which is primarily utilized in reticuloendothelial system imaging due to its affinity for macrophages found in the liver and spleen.

In this context, the liver's dominant percentage reflects its critical role in filtering blood, where colloidal particles are trapped. The spleen's contribution is also significant as it serves a similar function. The proportion of uptake in the bone marrow, while present, is quite small in relation to that of the liver and spleen, which is consistent with the biodistribution observed in practice. This understanding is vital for interpreting imaging results and making clinical decisions regarding the use of Tc sulfur colloid in diagnostic procedures.