Lower accuracy of Tl-201 SPECT in women is not improved by size-based normal databases or Wiener filtering

Abstract

Background. We have shown that the diagnostic accuracy of quantitative single photon emission computed tomography (SPECT) thallium 201 myocardial perfusion imaging is lower in women than in men and that much of the difference can be explained by the smaller size of the left ventricle in women. Therefore attempts at improving the accuracy of myocardial perfusion imaging in women should focus on the problem of lower accuracy in patients with small chamber size. We evaluated two strategies for this: size- and gender-based normal databases and inverse filtering with the Wiener filter. Methods and Results. We identified 618 patients undergoing exercise SPECT Tl-201 who either had a low pre-test probability of coronary artery disease or had catheterization-documented disease. Their images were analyzed on the basis of gender and chamber size: both gender and size- and gender-based normal databases were created. The studies were analyzed quantitatively, and the accuracy was evaluated by use of the area under the receiver operating characteristic (ROC) curve. Chamber size was significantly lower in women (size index 69 ± 22 women vs 96 ± 28 men; P < .0001). The accuracy of myocardial perfusion imaging was lower in women compared with men (ROC area: 0.92 ± 0.01 men vs 0.85 ± 0.03 women; P = .03), and there was an even greater difference in accuracy between patients with large versus small chamber size (ROC area: 0.94 ± 0.01 large vs 0.81 ± 0.03 small; P < .001). There was no improvement in the diagnostic accuracy either in women or in patients with small chamber size when a size- and gender-based normal database, Wiener filter, or the Wiener filter with a size- and gender-based normal database was used. Conclusion. The left ventricular chamber size in women is smaller than that in men. There is a significant difference in the accuracy of quantitative SPECT Tl-201 between men and women and an even greater difference between patients with large versus small chamber size. Neither size- and gender-based databases nor Wiener filtering significantly improves accuracy in women or in patients with small chamber size.