*2.7.1 Chemisorption mechanism of 99mTc-PYP*

99mTc-PYP is used for the acute myocardial infarction imaging is an example of Chemisorption mechanism of localization. Myocardial infarction starts when myocardial cells turn out to be necrotic, calcium ions influx create into the cells. Circulating phosphate ions present in body reacts with the Ca2+ ions and Ca3 (PO4)2 crystals are formed. Resulting calcium phosphate crystals formed hydroxyapatite present on bone tissues. 99mTc-PYP binds irreversibly and avidly to calcium phosphate crystals at the infarct periphery where some perfusion is maintained as shown in **Figure 7**. After two hours of post injection imaging takes place [34].
