Effects of scatter subtraction on detection and quantitation in hepatic SPECT

The purpose of this investigation was to examine the effects of subtractive scatter compensation methods on lesion detection and quantitation. Methods : Receiver operating characteristic (ROC) methodology was used to measure h uman observer detection accuracy for tumors in the liver using synthetic im ages. Furthermore, ROC results were compared with mathematical models for d etection and activity quantitation to examine (a) the potential for predict ing human performance and (b) the relationship between the detection and qu antitation tasks. Images with both low and high amounts of scatter were com pared with the ideal case of images of primary photons only (i.e., perfect scatter rejection) and with images corrected by subtracting a scatter image estimated by the dual photopeak window method. Results: With low contrast tumors in a low count background, the results showed that scatter subtracti on improved quantitation but did not produce statistically significant incr eases in detection accuracy. However, primary images did produce some stati stically significant improvements in detection accuracy when compared with uncorrected images, particularly for high levels of scatter. Conclusion: Al though scatter subtraction methods may provide improved activity quantitati on, they may not significantly improve detection for liver SPECT The result s imply that significant improvement in detection accuracy for the conditio ns tested may depend on the development of gamma cameras with better scatte r rejection.