What is the normal biodistribution of Tc HMPAO tagged WBCs?

• A. Liver, spleen, lungs, bone marrow, bladder
• B. Heart, kidneys, brain, liver, spleen
• C. Bone, muscles, skin, lungs, kidneys
• D. Pancreas, spleen, bladder, stomach, intestines

Answer: (A)

The normal biodistribution of Technetium-99m (Tc-99m) Hexamethylpropyleneamine Oxime (HMPAO) tagged white blood cells (WBCs) is characterized primarily by their localization in the liver, spleen, lungs, bone marrow, and bladder. This distribution reflects the biological behavior of WBCs, which play a crucial role in the immune response.

When labeled with Tc-99m HMPAO, WBCs tend to accumulate in areas where there is immune activity or inflammation, due to their natural movement toward sites of infection or tissue damage. The liver and spleen are particularly significant because they are major sites for the filtering and removal of damaged or non-functioning blood cells, and they also contain many immune cells that respond to infections or foreign substances.

The lungs are involved due to the presence of circulating white blood cells that can migrate here during pulmonary infections or conditions. Bone marrow contains a large population of white blood cells, thus contributing to their distribution when radiolabeled. Finally, the bladder may accumulate some radioactivity as it is where excess radiopharmaceutical is excreted from the body after circulation.

Understanding this normal biodistribution is key for interpreting imaging studies involving Tc-