Improved sensitivity in the quantitative diagnosis of ischemia based on end-systolic images obtained by gated SPECT

The purpose of this study was to assess the improvement in sensitivity of the quantitative diagnosis of ischemia based on end-systolic images obtained by electrocardiogram (ECG)-gated myocardial SPECT using 99mTc-tetrofosmin. After the intravenous infusion of 740 MBq of 99mTc-tetrofosmin during stress, we obtained ECG-gated myocardial SPECT images in 17 patients with normal coronary arteries and 81 patients with ≥75% coronary artery stenosis. After reconstructing end-systolic, end-diastolic, and summed ungated images, the short axis images were converted to polar maps, and quantitative defect scores were determined based on the extent and severity scores. In patients with coronary artery disease, their defect scores were significantly greater in end-systolic images than those in end-diastolic and ungated images. In contrast, no differences were observed in the defect scores in patients with normal coronary arteries. After determining the normal limit of the defect scores by using the patients with normal coronary arteries, the sensitivity for detecting ischemia was calculated for end-systolic, end-diastolic and ungated images. The sensitivity was also significantly higher for the end-systolic images than that in end-diastolic or ungated images. The quantitative diagnosis of ischemia using end-systolic images obtained using ECG-gated myocardial SPECT and 99mTc-tetrofosmin is more sensitive than other methods without a loss of specificity. Therefore the accuracy of the diagnosis of myocardial ischemia is improved by using end-systolic images. (author)