Authors: J Hoffend G Linke A Mohammed C P Tiefenbacher M Eisenhut U Haberkorn
Publish Date: 2003/02/07
Volume: 30, Issue: 4, Pages: 494-501
Abstract
Myocardial perfusion singlephoton emission tomography SPET performed with cationic technetium99m complexes indicates ischaemic areas as cold lesions By contrast nitroimidazole derivatives labelled with fluorine18 or 99mTc have recently shown promising results for hot spot imaging of ischaemic myocardium This study evaluates 99mTcOBATNI a new 99mTc complex comprising the nitroimidazole ligand 210dimercapto210dimethyl48diaza642nitroimidazolylbutylundecane in a lowflow in vivo model of myocardial ischaemia in thoracotomised rats To elucidate the influence of the 2nitroimidazole group on ischaemiainduced uptake comparisons with ligand derivatives were performed where a the 2nitro group was deleted 99mTcOBATI b the 2nitroimidazole functionality was replaced by a Br atom 99mTcOBATBr and c the 99mTcOBAT moiety was replaced by an iodine125 iodophenoxybutyl ligand 125IPNI The radiolabelled compounds were iv injected 15 min after reducing resting myocardial blood flow by 50–60 and the uptake of radioactivity was assessed 90 min post injection Autoradiography of left ventricular shortaxis slices showed median uptake ratios of ischaemic/nonischaemic myocardium I/N of 34 45 and 34 for 99mTcOBATNI 99mTcOBATI and 99mTcOBATBr respectively In contrast 125IPNI was not preferentially taken up by ischaemic myocardium Accumulation of 99mTcOBATNI in ischaemic heart regions was comparable to that in the liver Biodistribution studies showed a median uptake of 065 ID/g of 99mTcOBATNI in ischaemic tissue and an I/N of 33 On planar images of the thorax and upper abdomen the ischaemic hearts were visualised faintly the median heart to lung count ratio for 99mTcOBATNI was 17 and the median heart to liver count ratio was 10 We conclude that uptake of 99mTcOBATNI in ischaemic myocardium does not depend on the nitroimidazole moiety but is intrinsic to the BAT complex Clinical use of the 99mTcOBATlabelled tracers seems unlikely owing to their low uptake and their low ischaemic tissue contrast on planar images in vivo
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