Increased levels of Al3+ in Tc99m eluate used to prepare a sulfur colloid tracer may cause concentration in which organ?

Increased levels of Al3+ (aluminum ions) in the Technetium-99m (Tc-99m) eluate used for preparing a sulfur colloid tracer can lead to specific organ concentration, particularly in the lungs. This phenomenon is tied to the behavior of sulfur colloids in the presence of impurities like aluminum.

When sulfur colloid is labeled with Tc-99m, the intention is typically for it to serve as a radiotracer for imaging the reticuloendothelial system (RES), predominantly in the liver and spleen. However, when Al3+ contaminates the eluate, it can affect the distribution of the sulfur colloid. Aluminum ions can disrupt the normal particle size and structure of the colloid, leading to altered biodistribution.

Particles formed in the presence of excess aluminum may be larger or more irregularly shaped, making them less likely to be taken up by the liver or spleen. Instead, these modified colloidal particles can accumulate in the lungs due to their tendency to interact with lung capillaries or alveolar tissue, leading to an unexpected localization of the tracer. This is critical because it highlights the importance of purifying the Tc-99m eluate to minimize aluminum levels, ensuring