Quantitative evaluation of manganese-52m as a myocardial perfusion tracer in pigs using positron emission tomography.

There is a need for a quantitative myocardial perfusion agent that does not require an on-site cyclotron. Early studies with manganese demonstrated that this trace metal is of potential use for myocardial imaging. 52mMn can be produced in a 52Fe-52mMn generator and is suitable for positron emission tomographic (PET) imaging. The purpose of this study was to evaluate 52mMn with regard to its potential to quantitatively assess myocardial perfusion. Dynamic PET imaging was performed in six pigs with various doses of dipyridamole to increase blood flow. Retention (R) and model-based K1 values were correlated with microsphere blood flow. The models consisted of one (K1, k2) and two (K1, k2, k3) tissue compartments. Anterior, lateral and septal regions showed a good myocardium-to-background ratio; the evaluation of the inferior wall was impaired by high liver uptake. Linear regression yielded the following equations: K1=1.152 flow+0.059 (r=0.92), R=0.069 flow+0.034 (r=0.84). Based on these regressions, K1 increased 2.7-fold and R 2.6-fold in the examined flow range of 0.5-2 ml/min/g (fourfold increase), demonstrating an underestimation of higher flow rates by both measures. It is concluded that 52mMn allows the qualitative assessment of myocardial perfusion but does not meet the requirements of a quantitative myocardial perfusion agent.