title: [(18)F]FDG PET/CT outperforms [(18)F]FDG PET/MRI in differentiated thyroid cancer.
abstract: OBJECTIVE
  To evaluate the diagnostic potential of PET/MRI with [(18)F]FDG in comparison to PET/CT in patients with differentiated thyroid cancer suspected or known to have dedifferentiated.
  
  
  METHODS
  The study included 31 thyroidectomized and remnant-ablated patients who underwent a scheduled [(18)F]FDG PET/CT scan and were then enrolled for a PET/MRI scan of the neck and thorax. The datasets (PET/CT, PET/MRI) were rated regarding lesion count, conspicuity, diameter and characterization. Standardized uptake values were determined for all [(18)F]FDG-positive lesions. Histology, cytology, and examinations before and after treatment served as the standards of reference.
  
  
  RESULTS
  Of 26 patients with a dedifferentiated tumour burden, 25 were correctly identified by both [(18)F]FDG PET/CT and PET/MRI. Detection rates by PET/CT and PET/MRI were 97 % (113 of 116 lesions) and 85 % (99 of 113 lesions) for malignant lesions, and 100 % (48 of 48 lesions) and 77 % (37 of 48 lesions) for benign lesions, respectively. Lesion conspicuity was higher on PET/CT for both malignant and benign pulmonary lesions and in the overall rating for malignant lesions (p < 0.001). There was a difference between PET/CT and PET/MRI in overall evaluation of malignant lesions (p < 0.01) and detection of pulmonary metastases (p < 0.001). Surgical evaluation revealed three malignant lesions missed by both modalities. PET/MRI additionally failed to detect 14 pulmonary metastases and 11 benign lesions.
  
  
  CONCLUSIONS
  In patients with thyroid cancer and suspected or known dedifferentiation, [(18)F]FDG PET/MRI was inferior to low-dose [(18)F]FDG PET/CT for the assessment of pulmonary status. However, for the assessment of cervical status, [(18)F]FDG PET/MRI was equal to contrast-enhanced neck [(18)F]FDG PET/CT. Therefore, [(18)F]FDG PET/MRI combined with a low-dose CT scan of the thorax may provide an imaging solution when high-quality imaging is needed and high-energy CT is undesirable or the use of a contrast agent is contraindicated.
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany. vrachal@uni-muenster.de.
authors.forename: Alexis
authors.initials: A
authors.lastname: Vrachimis
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.
authors.forename: Matthias Christian
authors.initials: MC
authors.lastname: Burg
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wenning
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Allkemper
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Weckesser
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.|European Institute for Molecular Imaging, Westfälische Wilhelms University Münster, Waldeyerstrasse 15, 48149, Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schäfers
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149, Münster, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Stegger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: DTC; FDG; PET/CT; PET/MRI