Effect of attenuation correction on lesion detection using a hybrid PET system
Tocharoenchai, C.; Tsui, B.M.W.; Frey, E.C.; Wang, W-Tung.
Journal of the Medical Association of Thailand 88(1): 96-102
2005
ISSN/ISBN: 0125-2208 PMID: 15960226 Document Number: 2241
Objective: The purpose of this study was to investigate the effect of attenuation correction (AC) on lesion detection for a hybrid PET system.Material and Method. Experimental list-mode data were acquired from hot spheres inside a uniform cylindrical phantom with an elliptical cross-section using a Siemens E. CAM+ dual-camera hybrid PET system, Spheres with inner diameters of 0.8- and 1-cm and the cylindrical phantom were filled with F-18 to simulate lesions with lesion-to-background (L/B) ratios of 14:1 and 8:1, respectively, found in clinical PET studies. The list-mode data of each sphere size were regrouped into sinograms with peak-to-peak energy window settings at 30% and 20% for the 0.8- and 1-cm diameter lesion, respectively. They were then rebinned using the single slice rebinning method Attenuation correction was applied assuming uniform attenuation, The sinograms with and without A C were reconstructed using 5 iterations of OS-EM algorithm with 8 angles/subset and posfiltered with a Butterworth filter with n = 5 and fc = 0.52 cycles/cm. Human observer performance study and localization receiver operating characteristic (LROC) analysis were used to evaluate the reconstructed images for maximum lesion detection. Average areas under the LROC curves across 8 observers obtained with and without AC were determined The null hypothesis that there was no difference between with AC and without AC was tested using a two-tailed t-test with 95% confidence interval.Results: The results indicated that for the 0.8-cm lesion with 14:1 L/B ratio, the A(LROC) decreases from 0.66 to 0.62 when AC is applied as compared to without AC and from 0.69 to 0.63 for the 1.0-cm lesion with 8:1 L/B ratio, but no statistical difference (p > 0.05).Conclusion: The authors conclude that for a phantom with hot lesions embedded in a uniform background AC decreases lesion delectability compared to without AC using a hybrid PET system for small lesion sizes.
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