Stress and rest myocardial SPET quantification with 201T1 and 99Tcm-tetrofosmin: A comparison

99Tc m -tetrofosmin is a new myocardial perfusion agent that has excellent physical and pharmacokinetic characteristics for performing tomographic myocardial perfusion studies. The aim of this study was to compare the behaviour of 99 Tc m -tetrofosmin and 201 Tl in the assessment of ischaemia and viability in patients with previous myocardial infarction. Twenty consecutive patients who had suffered infarction and been referred for assessment of ischaemia and myocardial viability were enrolled into the study. Each patient underwent two stress tests performed no more than 10 days apart, one with a 201 Tl exercise-reinjection-redistribution method and one with a 99 Tc m -tetrofosmin short protocol (exercise-rest). The results were quantified using polar maps to represent images for stress, rest and reversibility. The post-stress images showed there was a slight tendency to overestimate defect size with 99 Tc m -tetrofosmin in the lateral region (P < 0.006). We found no significant differences between the two tracers when comparing reversibility. The same defect sizes at rest were obtained when the maps for 201 Tl with uptake of 50% were compared with those for 99 Tc m -tetrofosmin with uptake of 45%. Agreement between the two agents for assessment of viability was 93%. We conclude that the quantitative assessment of myocardial ischaemia and uptake of 99 Tc m -tetrofosmin at rest are comparable to those obtained with 201 Tl in patients who have suffered myocardial infarction.