M. Eiber, A. Martinez-Möller, M. Souvatzoglou, E. Rummeny, M. Schwaiger, A. Beer, S. Nekolla Value of a Dixon based MR-PET attenuation correction sequence for the localization and evaluation of PET positive lesions Journal of Nuclear Medicine 2011, 51 (suppl. 1), p105. Proceedings of Annual Meeting of Society of Nuclear Medicine (SNM 2011), San Antonio, TX, USA, June 2011 (bib)
	Objectives Dixon-based MR imaging with a rapid low-resolution breathhold sequence has recently been proposed as technique for MR based attenuation correction (MR-AC) for MR-PET. In this study, the potential contribution of this sequence for anatomical correlation of PET positive lesions was evaluated compared to low-dose CT. Methods: 35 patients routinely scheduled for oncological staging underwent 18F-FDG PET/CT and a 2-point Dixon 3D VIBE T1 weighted MR sequence on a 3T clinical scanner at the same day. Two PET datasets reconstructed using attenuation maps from low-dose CT (PETAC_CT) or simulated MR based segmentation (PETAC_MR) were evaluated by two experienced readers for focal PET positive lesions. The certainty for the correlation with anatomical structures was judged in the low-dose CT and Dixon based MRI on a four-point-scale (0-3). In addition, the standardized uptake values (SUVs) for PETAC_CT and PETAC_MR were compared. Results: No significant difference could be found for all 81 PET positive lesions in low-dose CT compared to Dixon based MR concerning anatomical localization (mean 2.51±0.85 and 2.37±0.87, respectively; p=0.1909). However, CT tended to be superior for small lymph nodes, bone metastases and pulmonary nodules, while Dixon based MR proofed advantageous for soft-tissue pathologies like head/neck tumors and liver metastases. For the PETAC_CT and PETAC_MR based SUVs (mean 6.36±4.47 and 6.31±4.52, respectively) a nearly complete concordance with a highly significant correlation was found (r=0.9975, p<0.0001). Conclusions: Dixon based MR imaging for MR-AC allows for anatomical allocation of PET-positive lesions similar to low-dose CT in conventional PET/CT. Thus, this approach appears to be useful for future MR-PET for body regions not fully covered by diagnostic MRI due to potential time constraints.</TD>
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