It has been shown in clinical studies that for subjects with a low likelihood of coronary artery disease (CAD), attenuation correction (AC) improves the specificity of defect detection in the inferior wall (right coronary artery [RCA] region). The aim of this study was to investigate the effect of AC on the visual interpretation of the RCA and anteroseptal (corresponding to the left anterior descending artery [LAD]) regions in CAD patients.
Methods: Fifty-six patients with suspected CAD underwent 20Tl stress/4 h-delayed imaging SPECT using a simultaneous 201Tl emission/99mTc transmission imaging protocol. Images were reconstructed using the maximum likelihood-expectation maximum algorithm without and with AC. The stress/4 h-delayed images were interpreted blindly for reversible or fixed defects in the RCA and LAD regions by three experienced physicians. Coronary angiography, electrocardiography and enzyme findings were used to establish diagnoses of ischemia or infarction, and receiver operating characteristic (ROC) analyses were performed.
Results: Statistical testing of ROC curve areas showed that defect detection performance improved with AC when compared with performance without AC in the RCA region. This was mainly the result of a systematic increase in specificity of 12% or more (for any observer and any type of defect) for a similar sensitivity (no definite change in sensitivity values). However, defect detection performance significantly decreased in the LAD territory with AC images (P < 0.05) because of a systematic decrease in sensitivity of 20% or more, with no consistent change in specificity. Similar trends were observed when reversible and fixed defects were considered separately.
Conclusion: AC significantly affects the visual interpretation of 201Tl stress/4 h-delayed SPECT images. This study confirmed the increase in specificity obtained with AC in the RCA territory. However, in the population considered, the studied AC was deleterious for the LAD territory assessment.