Background-Soft tissue attenuation is a prominent cause of single-photon emission computed tomography (SPECT) imaging artifacts, which may result in reduced diagnostic accuracy of myocardial perfusion imaging. A method incorporating simultaneously acquired transmission data permits nonuniform attenuation correction and when incorporating scatter correction and resolution compensation may substantially reduce interpretive errors. Methods and Results-A prospective multicenter trial was performed recruiting patients with angiographically documented coronary disease (nϭ96) and group of subjects with a low likelihood of disease (nϭ88). The uncorrected and attenuation/scatter corrected images were read independently, without knowledge of the patient's clinical data. The detection of Ն50% stenosis was similar using uncorrected perfusion data or with attenuation/ scatter correction and resolution compensation (visual or visual plus quantitative analysis), 76% versus 75% versus 78%, respectively (PϭNS). The normalcy rate, however, was significantly improved with this new methodology, using either the corrected images (86% vs 96%; Pϭ0.011) or with the corrected data and quantitative analysis (86% vs 97%; Pϭ0.007). The receiver operator characteristic curves were also found to be marginally but not significantly higher with attenuation/scatter correction than with tradition SPECT imaging. However, the ability to detect multivessel disease was reduced with attenuation/scatter correction. Regional differences were also noted, with reduced sensitivity but improved specificity for right coronary lesions using attenuation/scatter correction methodology. Conclusions-This multicenter trial demonstrates the initial clinical results of a new SPECT perfusion imaging modalityincorporating attenuation and scatter correction in conjunction with 99m Tc sestamibi perfusion imaging. Significant improvements in the normalcy rate were noted without a decline in overall sensitivity but with a reduction in detection of extensive coronary disease. (Circulation. 1999;99:2742-2749.)

SPECT ERNA provides accurate, reproducible assessment of RV volumes and EF and should prove useful in evaluating the magnitude of RV dysfunction in patients and in providing an objective means with which to assess the results of therapeutic interventions.

We determined the sequence and timing of inward ventricular wall motion by least-square phase analysis of radionuclide cineangiograms in 10 patients with left bundle branch block (LBBB), five patients with right bundle branch block (RBBB) and 11 patients with normal conduction. All LBBB and RBBB patients had normal coronary arteries and no segmental wall motion abnormalities. The left ventricle (LV) was divided into eight segments and the right ventricle (RV) into three; sequence and timing were scored by three observers. In normal subjects, wall motion begins in either or both ventricles and ends in the LV or both ventricles. In patients with LBBB it begins in the RV and ends in the LV; in patients with RBBB is begins in the LV and ends in the RV or both ventricles. The intraventricular wall motion is also altered in the ventricle ipsilateral to a bundle branch block. In LBBB, the mean time of onset of LV wall motion is delayed 1.9 frames (38 msec), whereas RV wall motion is normal. In RBBB, the onset of RV wall motion is delayed 1.3 frames (26 msec), whereas LV wall motion is not delayed.

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