title: PET/MR Outperforms PET/CT in Suspected Occult Tumors.
abstract: BACKGROUND
  To compare the diagnostic accuracy of PET/MR and PET/CT in patients with suspected occult primary tumors.
  
  
  METHODS
  This prospective study was approved by the institutional review board. Sequential PET/CT-MR was performed in 43 patients (22 male subjects; median age, 58 years; range, 20-86 years) referred for suspected occult primary tumors. Patients were assessed with PET/CT and PET/MR for the presence of a primary tumor, lymph node metastases, and distant metastases. Wilcoxon signed-rank test was performed to compare the diagnostic accuracy of PET/CT and PET/MR.
  
  
  RESULTS
  According to the standard of reference, a primary lesion was found in 14 patients. In 16 patients, the primary lesion remained occult. In the remaining 13 patients, lesions proved to be benign. PET/MR was superior to PET/CT for primary tumor detection (sensitivity/specificity, 0.85/0.97 vs 0.69/0.73; P = 0.020) and comparable to PET/CT for the detection of lymph node metastases (sensitivity/specificity, 0.93/1.00 vs 0.93/0.93; P = 0.157) and distant metastases (sensitivity/specificity, 1.00/0.97 vs 0.82/1.00; P = 0.564). PET/CT tended to misclassify physiologic FDG uptake as malignancy compared with PET/MR (8 patients vs 1 patient).
  
  
  CONCLUSIONS
  PET/MR outperforms PET/CT in the workup of suspected occult malignancies. PET/MR may replace PET/CT to improve clinical workflow.
authors.affiliation: From the *Department of Nuclear Medicine, University Hospital Zurich/University of Zurich, Zurich, Switzerland; †Department of Radiology, Nippon Medical School, Tokyo, Japan; ‡GE Healthcare, Waukesha WI; §Department of Diagnostic and Interventional Radiology, University Hospital Zurich/University of Zurich, Zurich; and ∥Department of Medical Radiology, Clinic of Neuroradiology, University Hospital Zurich/University of Zurich, Zurich, Switzerland.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Sekine
authors.forename: Felipe de Galiza
authors.initials: FG
authors.lastname: Barbosa
authors.forename: Bert-Ram
authors.initials: BR
authors.lastname: Sah
authors.forename: Cäcilia E
authors.initials: CE
authors.lastname: Mader
authors.forename: Gaspar
authors.initials: G
authors.lastname: Delso
authors.forename: Irene A
authors.initials: IA
authors.lastname: Burger
authors.forename: Paul
authors.initials: P
authors.lastname: Stolzmann
authors.forename: Edwin E
authors.initials: EE
authors.lastname: Ter Voert
authors.forename: Gustav K
authors.initials: GK
authors.lastname: von Schulthess
authors.forename: Patrick
authors.initials: P
authors.lastname: Veit-Haibach
authors.forename: Martin W
authors.initials: MW
authors.lastname: Huellner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009382:Neoplasms, Unknown Primary / Q000000981:diagnostic imaging* / Q000473:pathology; D000072078:Positron Emission Tomography Computed Tomography; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18