Receptor Binding
C-11-dopamine
Picture a molecule locking into a receptor (like a key into a lock).
Active Transport
I-131 (thyroid)
Imagine pushing a substance uphill using energy (ATP).
Compartmental Localization
99mTc-labeled RBC (heart scan)
Picture red blood cells in a heart scan (like a compartment inside the heart).
Ion Exchange
99mTc-phosphonate (bone)
Think of bone binding to radioactive particles, like glue sticking to it.
Phagocytosis
99mTc-sulfur colloid (RES system)
Visualize cells eating particles like Pac-Man.
Capillary Blockade
99mTc-MAA (lungs)
Picture particles stuck in small capillaries, like a clog in a pipe.
Cell Sequestration
99mTc-RBC (spleen)
Imagine the spleen capturing damaged red blood cells.
Chemotaxis
111-In-labeled leukocytes (infection)
Picture infection attracting phagocytes like a magnet.
Passive Diffusion
99mTc-DTPA (brain)
Visualize a substance moving naturally from high to low concentration, like water flowing downhill.
Metabolism
18-F-FDG (tumor activity)
Imagine cancer cells metabolizing glucose at a faster rate (like a factory running faster).