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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.

Four different methods of radiolabelling the anti-granulocyte monoclonal antibody MAb47 were compared and their influence on diagnostic value studied. The best clinical images were obtained following labelling with iodine-123 by the Iodogen method and direct labelling with technetium-99m after tris-(carboxyethyl)-phosphine treatment of MAb47 to achieve disulphide bridge reduction. 99mTc labelling using a specific ligand (MAb47-mtp), or a second method involving direct reduction with mercaptoethanol, led to an increased background activity in clinical studies, thus impeding the diagnosis of chronic disease. Fresh infections were clearly localized by all four preparations. The elimination of the activity from the blood was slower in the case of the iodinated MAb47, while the collected urine samples showed an excretion of about 10% of the injected activity per day independent of the labelling method. The results in terms of sensitivity and specificity were rather similar for all labelling methods and ranged from 90% to 99%.