Comparison of contrast enhanced PET/MRI and contrast enhanced PET/CT in patients with head and neck cancer

515 Objectives PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the diagnostic performance of contrast-enhanced (ce) MRI in patients with head and neck cancer in comparison with ceCT to characterize PET-positive lesions. Methods Eighty consecutive patients referred for primary staging or re-staging of head and neck cancer underwent sequential whole-body 18F-FDG PET with CT-based attenuation correction (AC), contrast-enhanced CT and conventional diagnostic MRI (2-point Dixon based T2 weighted and native/contrast enhanced T1 weighted sequences) of the head and neck in a tri-modality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI for their anatomical localization, conspicuity and additional information for characterisation. Results In 38 patients with at least one PET-positive lesion, 60 lesions were evaluated. No significant difference was found between MRI and CT regarding lesion localization. MRI performed significantly better than CT regarding conspicuity of tumors (Wilcoxon signed rank test, p Conclusions CeMRI outperformed ceCT in terms of conspicuity and characterization of PET-positive head and neck tumor lesions and performed similarly in cervical lymph node assessment. Hence, cePET/MRI has the potential to replace cePET/CT as the primary diagnostic imaging tool for the evaluation of head and neck cancers. Research Support GE Healthcare