title: Value of retrospective fusion of PET and MR images in detection of hepatic metastases: comparison with 18F-FDG PET/CT and Gd-EOB-DTPA-enhanced MRI.
abstract: The purpose of this study was to compare the accuracy of lesion detection and diagnostic confidence between (18)F-FDG PET/CT, gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI, and retrospectively fused PET and MRI (PET/MRI).
  
  
  METHODS
  Thirty-seven patients (mean age +/- SD, 60.2 +/- 12 y) with suspected liver metastases underwent PET/CT and Gd-EOB-DTPA-enhanced MRI within 0-30 d (mean, 11.9 +/- 9 d). PET and Gd-EOB-DTPA-enhanced MR image data were retrospectively fused. Images were reviewed independently by 2 readers who identified and characterized liver lesions using PET/CT, Gd-EOB-DTPA-enhanced MRI, and PET/MRI. Each liver lesion was graded on a 5-point confidence scale ranging from definitely benign (grade of 1) to definitely malignant (grade of 5). The accuracy of each technique was determined by receiver-operating-characteristic analysis. Histopathology served as the standard of reference for all patients with malignant lesions.
  
  
  RESULTS
  A total of 85 liver lesions (55 liver metastases [65%] and 30 benign lesions [35%]) were present in 29 (78%) of the 37 patients. Twenty-four (65%) of the 37 patients had liver metastases. The detection rate of liver lesions was significantly lower for PET/CT than for Gd-EOB-DTPA-enhanced MRI (64% and 85%; P = 0.002). Sensitivity in the detection and characterization of liver metastases for PET/CT, Gd-EOB-DTPA-enhanced MRI, PET/MRI in reader 1, and PET/MRI in reader 2 was 76%, 91%, 93%, and 93%, respectively; the respective specificity values were 90%, 100%, 87%, and 97%. The difference in sensitivity between PET/CT and PET/MRI was significant (P = 0.023). The level of confidence regarding liver lesions larger than 1 cm in diameter was significantly higher in PET/MRI than in PET/CT (P = 0.046). Accuracy values (area under the receiver-operating-characteristic curve) for PET/CT, Gd-EOB-DTPA-enhanced MRI, PET/MRI in reader 1, and PET/MRI in reader 2 were 0.85, 0.94, 0.92, and 0.96, respectively.
  
  
  CONCLUSIONS
  The sensitivity of Gd-EOB-DTPA-enhanced MRI and PET/MRI in the detection of liver metastases is higher than that of PET/CT. Diagnostic confidence was significantly better with PET/MRI than with PET/CT regarding lesions larger than 1 cm in diameter. Compared with Gd-EOB-DTPA-enhanced MRI, PET/MRI resulted in a nonsignificant increase in sensitivity and diagnostic confidence.
authors.affiliation: Institute of Diagnostic Radiology, University Hospital Zurich, Zurich, Switzerland. odonati@gmx.net
authors.forename: Olivio F
authors.initials: OF
authors.lastname: Donati
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Hany
authors.forename: Caecilia S
authors.initials: CS
authors.lastname: Reiner
authors.forename: Gustav K
authors.initials: GK
authors.lastname: von Schulthess
authors.forename: Borut
authors.initials: B
authors.lastname: Marincek
authors.forename: Burkhardt
authors.initials: B
authors.lastname: Seifert
authors.forename: Dominik
authors.initials: D
authors.lastname: Weishaupt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D019788:Fluorodeoxyglucose F18; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000556:secondary*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012015:Reference Standards; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014055:Tomography, Emission-Computed
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; C073590:gadolinium ethoxybenzyl DTPA; D019788:Fluorodeoxyglucose F18; D019786:Gadolinium DTPA