Which organ receives the highest dose from Tc MAA?

• A. Liver
• B. Spleen
• C. Kidneys
• D. Lungs

Answer: (D)

The lungs receive the highest dose from technetium-99m labeled macroaggregated albumin (Tc MAA) due to the nature of its intended use in medical imaging, particularly in the evaluation of pulmonary perfusion. When Tc MAA is administered intravenously, the particles combine with the pulmonary capillaries, where they ultimately lodge, allowing for the assessment of blood flow through the lungs.

Given that the macroaggregated albumin is specifically designed to be trapped within the alveolar capillary bed, the radiation dose delivered to the lung tissue is significantly higher than to other organs. This characteristic makes lung imaging particularly effective, as the distribution of the radiopharmaceutical provides valuable information about pulmonary blood flow and function.

In contrast, other organs such as the liver, spleen, and kidneys may also receive radiation exposure, but the dose is comparatively lower due to either their anatomical function or the distribution patterns of Tc MAA. This distinct property of Tc MAA that causes it to preferentially localize in the lungs is the key reason for the organ's elevated radiation dose.