Optimum threshold values of Tl-201 SPET in the determination of the left ventricular border and extent of myocardial infarction

The aim of this study was to determine the optimum threshold value of the l eft ventricular border and the extent of myocardial infarction using quanti tative Tl-201 Single photon emission tomography (SPET). We used the unfolde d map method to determine the size of the left ventricle and the extent of myocardial infarction in 10 patients, because it has been shown to be super ior to the conventional polar map method. The relative differences in the s ize of the left ventricle and extent of infarction between Tl-201 SPET and post-mortem examination were calculated. The optimum threshold value was de termined when the relative difference = 0%. There was an excellent correlat ion between scintigraphic and post-mortem left ventricular size at a thresh old value of 53% (r = 0.91, P < 0.001); an excellent correlation was also o bserved between scintigraphic and post-mortem infarct size at a threshold v alue of 55% (r = 0.93, P < 0.03). The optimum threshold value in determinin g left ventricular size using Tl-201 SPET is 53% and that in determining in farct size is 55%. ((C) 1999 Lippincott Williams & Wilkins).