Tc99mMAG3

Technetium-99m MAG3 (mercaptoacetyltriglycine) is a radiopharmaceutical used in renal scintigraphy. It consists of technetium-99m labeled MAG3, administered intravenously. The kit contains MAG3 ligand and a stannous reducing agent; labeled with Tc-99m pertechnetate to yield Tc-99m MAG3 with high radiochemical purity.

Pharmacokinetics: After injection, Tc-99m MAG3 is rapidly cleared from plasma and taken up by the kidneys primarily by tubular secretion via organic anion transporters in the proximal tubules; it is excreted in urine with minimal protein binding and limited hepatic uptake.

Clinical uses: It is used for dynamic renal scintigraphy to assess renal perfusion, function, and drainage. It is widely used for diuretic renography to distinguish hydronephrosis due to obstruction from nonobstructive dilation, and to estimate differential renal function.

Procedure: Imaging is performed with a gamma camera immediately after injection, obtaining dynamic frames (usually 1-2 minute frames) for about 20-40 minutes. A diuretic (commonly furosemide) may be administered to provoke drainage for obstruction evaluation. Time-activity curves are generated to assess uptake and excretion.

Safety and comparison: Tc-99m MAG3 imparts a low radiation dose. It has favorable pharmacokinetics for renal imaging and is generally well tolerated; compared with Tc-99m DTPA, which mainly reflects glomerular filtration, MAG3 provides information on tubular secretion and drainage, making it preferable for renography.