What is the mechanism of localization for filtered Tc Sulfur Colloid?

• A. Chemical binding
• B. Mechanical, following lymph drainage
• C. Electrostatic attraction
• D. Passive diffusion

Answer: (B)

Filtered Tc Sulfur Colloid localizes primarily through a mechanical mechanism, specifically by following lymph drainage. This radiopharmaceutical is composed of small particles that are introduced into the body, typically for imaging purposes such as lymphoscintigraphy. Once administered, the particles are too large to be absorbed directly into the bloodstream and are instead carried by the lymphatic system.

As the Tc Sulfur Colloid particles move through the lymphatic vessels, they become trapped in the lymph nodes. This trapping occurs due to the natural structural characteristics of lymph nodes, which effectively filter these kinds of particulate materials. The lymphatic drainage pathway thus plays a crucial role in the localization of the radiopharmaceutical, allowing for visualization of lymphatic flow and the evaluation of lymph nodes during imaging studies.

The other mechanisms, such as chemical binding, electrostatic attraction, or passive diffusion, do not apply in this context because they do not accurately describe how Tc Sulfur Colloid behaves in the lymphatic system. Chemical binding would imply a more permanent attachment to specific tissue or cells, while electrostatic attraction involves interactions at a molecular level that are not involved in this mechanical process. Passive diffusion, which is the movement of molecules across a membrane from an area of higher concentration to one of lower