Table 1.

Comparison of different radionuclide agents currently in routine clinical use for myocardial perfusion imaging

Radionuclide	Half life	Activity administered	Effective dose	Mechanism of myocardial uptake	Redistribution	Comments
201Tl	72 hours	60–80 MBq	15–20 mSv	ATPase-K+ myocyte cell membrane integrity required	Redistributes	Poor quality images; difficult to gate. Prognostic data available; redistribution advantageous for viability detection
99mTc-sestamibi	6 hours	800 MBq	8 mSv	Myocyte mitochondria	Minimal	Versatile agent; increasing use; viability detection validated against 201Tl, dobutamine stress echocardiography, and PET
99mTc-tetrofosmin	6 hours	800 MBq	8 mSv	Not known	Nil	Poorer extraction with vasodilator stress; underestimates ischaemic burden; improved extracardiac clearance suggested

Mbq, megabecquerel; mSv, millisievert; PET, positron emission tomography.