Validation of quantitative accuracy of the post-injection transmission-based and transmissionless attenuation correction techniques in neurological FDG-PET

Abstract

We evaluated the quantitative accuracy of the post-injection transmission-based segmented attenuation correction (SAC) technique and transmissionless calculated attenuation correction (CAC) technique in both 2D and 3D scanning for the brain, and compared the results with those obtained using the pre-injection transmission-based measured attenuation correction (MAC) technique, which is generally accepted as the 'gold standard'. We examined [18F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) on both a cylindrical phantom and in 10 patients with epilepsy. The statistical analyses were performed using both the region of interest (ROI) method and statistical parametric mapping (SPM). In the ROI analysis, [18F] activity concentration values obtained by the SAC technique were well correlated with those obtained by the MAC technique (2D, R2=0.94; 3D, R2=0.98; P<0.001), although these values were underestimated over the entire brain. The CAC technique was also found to have significant correlation with the MAC technique (2D, R2=0.84; 3D, R2=0.86; P<0.001), but this technique showed apparent overestimation or underestimation in several parts of the brain. In the SPM analysis, there were no significant differences between the SAC and MAC technique, while those values obtained by the CAC technique were significantly lower in the parieto-occipital region and higher in the lower frontal region (P<0.001, uncorrected). The SAC technique was superior to the CAC technique in both 2D and 3D scanning, although we found that both the SAC and CAC techniques had some problems in quantitative evaluation. We considered that the SAC technique may yield adequate qualitative measurements of the [18F] activity concentration value after global normalization.