A comparison of Tl-201 stress-reinjection-prone SPECT and Tc-99m-sestamibigated SPECT in the differentiation of inferior wall defects from artifacts

The frequency of false positive results obtained from the inferior myocardi al region using single photon emission computed tomography (SPECT) myocardi al perfusion scintigraphy is significantly higher than that obtained from o ther regions. Several methods, such as prone-position imaging, have been pr oposed to overcome this diagnostic problem. The aim of the present study wa s to compare the results of Tc-99m-sestamibi gated SPECT and Tl-201 prone S PECT in the differentiation of inferior wall artifacts from true defects. F or this purpose, 38 subjects, whose coronary anatomies were documented on a ngiography, underwent same-day stress-rest Tc-99m-sestamibi gated SPECT and Tl-201 stress-reinjection-prone (whose standard supine images demonstrated fixed defects on the inferior wall) SPECT. Gated SPECT was performed by 8 frames per cycle acquisition over a 180 degrees rotation on 30 projections. Four gated SPECT slices were obtained on mid-ventricular vertical long axi s, horizontal long axis and apical and basal short axis planes, and display ed in cine-format. Both Tl-201 prone imaging and Tc-99m-sestamibi gated ana lysis increased the specificity of inferior wall disease detection remarkab ly from 54% to 85% and 46% to 82%, respectively (P<0.05). The difference be tween diagnostic accuracies was not significant (80% and 82%, respectively) (P> 0.05). The positive predictive values for true defects were 96% for Tl -201 prone imaging and 94% for Tc-99m-sestamibi gated imaging. Based on seg mental analysis, the two modalities showed fair agreement (kappa = 0.44 for standard supine protocols, kappa = 0.46 for Tl-201 prone and Tc-99m-sestam ibi gated SPECT). It can be concluded that Tc-99m-sestamibi gated SPECT, re quiring only two-step acquisition, may potentially increase the test specif icity for coronary artery disease (CAD) of the inferior wall as well as doe s Tl-201 sh ess-reinjection-prone SPECT. By giving functional information, it seems the most practical method in daily use for supplying the most exte nsive information about patients with suspected or known CAD. ((C) 2000 Lip pincott Williams & Wilkins).