Technetium-99m-Pyrophosphate Myocardial Imaging

Abstract

Technetium-99m is the most widely used radioisotope in nuclear medicine presently. It has nearly ideal decay characteristics, including a half-life of 6 hr, monoenergetic and highly abundant gamma rays (140 keV, 90%) and absence of beta or alpha particle emission [1]. It is also easy to produce and readily available in generator form. It has the ability to complex with many organic and inorganic compounds [1]. Technetium-99m is the daughter product of ⁹⁹Mo. Molybdenum-99 has a half-life of 67 hr and undergoes both gamma and beta decay, the beta-decay leading to its daughter product ^99mTc. Tech-netium-99m can be separated easily from its parent product by simple solvent extraction with methylethylketone under basic conditions or by column chro-matography on an alumina column. Simple elution with isotonic saline brings ionic pertechnetate (^99mTcO₄) through the column, leaving ^99mMo behind, which, by its subsequent decay, generates more ^99mTc that can be eluted later. Technetium-99m stannous pyrophosphate was chosen as a potential imaging agent to identify acute myocardial infarcts with the rationale being that pyrophosphate might complex with calcium which is deposited in irreversibly damaged myocardial cells following acute myocardial infarction [2, 3].