Myocardial kinetics of potassium-38 in humans and comparison with copper-62-PTSM.

UNLABELLED: The aim of this study was to define the kinetics of 38K and its suitability to evaluate myocardial blood flow at rest and during pharmacological vasodilation in normal subjects. Potassium-38's kinetic characteristics were also compared to those of a 62Cu-pyruvaldehyde bis(n4-methyl-thio-semicarbazone) copper (II) (PTSM) flow tracer. METHODS: Potassium-38 and 62Cu-PTSM were injected at rest and after pharmacological vasodilation in six healthy volunteers. Dynamic PET acquisition was performed over 20 min and myocardial tracer retention calculated. Homogeneity of regional myocardial tracer distribution was also evaluated. RESULTS: High image quality of the heart was observed at rest and after dipyridamole with both tracers. Potassium-38 demonstrated prolonged myocardial retention with minimal lung and liver accumulation. In contrast to 38K, 62Cu-PTSM demonstrated high liver uptake which may hinder observation of the inferior wall of the myocardium. Copper-62-PTSM dipyridamole-to-rest retention ratio was 1.49. CONCLUSIONS: Potassium-38 and 62Cu-PTSM display suitable kinetics for the qualitative evaluation of blood flow and flow reserve in the human heart. Compared to 62Cu-PTSM, potassium-38, which does not show high liver uptake, may more accurately estimate blood flow in the inferior wall of the heart. However, accurate quantification of myocardial blood flow using 38K or 62Cu-PTSM retention appears to be limited to decreasing retention fraction at hyperhemic states.

Automated production of potassium-38 for the study of myocardial perfusion using positron emission tomography.

The 35Cl(alpha, n)38K nuclear reaction was developed for the routine cyclotron production of repeated multimillicurie batches of 38K for dynamic studies of regional tissue perfusion with positron emission tomography. The objective is to make this isotope available as an alternative to the use of [13N]NH3 and 82Rb for the investigation of flow in experimental and clinical use. A sodium chloride powder target mounted on a water-cooled nickel backing is bombarded with 26 MeV helium-4 ions at a maximum beam current of 25 microA. The target is remotely disconnected from the bombardment port, transported to a hot cell and entirely processed by a computer-controlled system within a total time of less than 4 min. The final pyrogen-free isotonic and sterile solution of 38K has a radionuclidic purity of more than 99.99%. A typical yield of 19 +/- 2 mCi of 38K is obtained at the end of a 30 min bombardment at 10 microA. The production rate at saturation can therefore be estimated to 2.05 +/- 0.2 mCi/microA.

Measurements of cell-mediated cytotoxicity on target cells labelled with the indium-111-oxine complex.

The preparation is given of an 111indium-oxine complex that is non toxic and can label reproductively various types of cells. They retain the label for long periods (24 hours and more). This method gives parallel results for cell-mediated cytotoxicity measurements to Chromium-51 labelling and is found to have wider uses. It can label cells that release 51Cr too fast, makes possible long term measurements of cytotoxicity and accurate counts on small numbers of target cells.