PROJECT TITLE :
Comparison of Template-Based Versus CT-Based Attenuation Correction for Hybrid MR/PET Scanners
Attenuation correction (AC) of cerebral PET information acquired in hybrid MR/PET scanners is still a challenge. To beat this problem we previously proposed a correction technique by getting template-primarily based attenuation maps (AM) using MR and ECAT PRECISE HR+ transmission scans. In the present study we investigated (a) the essential difference between template-based mostly and CT-based AC ways and (b) their influence on reconstructed PET pictures. The info of eleven subjects undergoing 18FDG imaging within the Siemens 3T MR-BrainPET scanner were used. Additionally, from all participants a CT scan of the entire head was acquired at the same day. These CT images were remodeled to CT-based mostly AMs. They were filtered by a 3D Gaussian kernel with three mm (BrainPET resolution) filter width, which was considered as reference. Comparisons between both AMs (CT-based mostly and template-primarily based) were performed by estimating the Dice coefficients D and calculating the numbers of true positive, true negative and false negative voxels. The BrainPET emission data were reconstructed with both AMs ( AMCT3mm and AMTemplate). All reconstructed PET pictures were scaled to standardized uptake values (SUVs) and normalized to the MNI brain for using the AAL-VOI Atlas analysis. Correlation plots with regression equation, coefficients of determination R2 and relative variations (RD) between AMCT3mm and therefore the AMTemplate were derived. The fraction of the general true positive voxels averaged over the 11 subjects was 80.4 ±seven.fivep.c for AMTemplate compared to AMCT3mm ( Dbone = 0.63 ±0.08; Dsoft - tissue = 0.85 ±0.08; Dair = zero.seventy nine ±0.04). A misclassification of bone as soft tissue and vice versa was evident within the comparison. The correlation plot of all VOIs considered (one,276 values) showed a mean R2 of zero.964 and a slope of 1.02. A mean RD of 1.thirty three ±zero.95p.c ( min = - zero.12p.c, max = a pair of.85p.c) was found. The template-primarily based AC technique proposed by our cluster shows considerable distinction- as compared to the higher resolution CT-based AM with respect to the Dice coefficients, in explicit in the classification of bone and soft tissue. However, this has no major influence on the reconstructed 18FDG PET information.
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