title: Disease activity and vascular involvement in retroperitoneal fibrosis: first experience with fully integrated 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging compared to clinical and laboratory parameters.
abstract: OBJECTIVE
  The aim of this study was to evaluate the value of fully integrated [18F]-FDG PET/MRI in the assessment of retroperitoneal fibrosis with regard to disease activity, extent and vascular involvement compared to clinical and laboratory parameters.
  
  
  METHODS
  Seventeen [18F]-FDG PET/MRI examinations were performed in fourteen patients. Qualitative (visual 4-point scale) and quantitative PET parameters (maximum standardised uptake value, SUVmax; target-background ratio, TBR) as well as RF thickness and volume were correlated to clinical and inflammatory parameters and compared between therapy-naïve patients and patients under immunosuppression. Evidence for associated large-vessel vasculitis was examined. Magnetic resonance angiography (MRA) was performed to detect aneurysms or stenoses.
  
  
  RESULTS
  Clinical parameters, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) only incompletely displayed inflammatory activity and did not correlate with PET/MRI parameters. In 29% (4/17) resp. 50% (8/16) of PET/MRI examinations active disease was detected although CRP resp. ESR were in the normal range. SUVmax, TBR and volume of the retroperitoneal mass differed significantly between therapy-naïve patients and patients under therapy (SUVmax p=0.004, TBR p=0.015, volume p=0.015), whereas thickness of the retroperitoneal mass did not (p=0.406). Large-vessel vasculitis was detected in 21% (3/14) and aortic aneurysms in 14% (2/14) of patients. Vasculitis occurred apart from the site of RF in two patients.
  
  
  CONCLUSIONS
  Whole body hybrid [18F]-FDG-PET/MRI is superior to clinical and inflammatory parameters in disease activity assessment of RF. There may be substantial disease activity despite inflammatory parameters in the normal range. Associated large-vessel vasculitis and aneurysms may occur apart from the site of RF.
authors.affiliation: Department of Nephrology and Rheumatology, Klinikum rechts der Isar, Technical University of Munich, Germany. klaus.thuermel@mri.tum.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Thuermel
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Einspieler
authors.affiliation: Department of Nephrology and Rheumatology, Klinikum rechts der Isar, Technical University of Munich, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Wolfram
authors.affiliation: Department of Nephrology and Rheumatology, Klinikum rechts der Isar, Technical University of Munich, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Moog
authors.affiliation: Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar, Technical University of Munich, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Meier
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.affiliation: Department of Nephrology and Rheumatology, Klinikum rechts der Isar, Technical University of Munich, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Heemann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001014:Aortic Aneurysm / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy; D001157:Arterial Occlusive Diseases / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy; D015415:Biomarkers / Q000097:blood; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D018836:Inflammation Mediators / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D015203:Reproducibility of Results; D012185:Retroperitoneal Fibrosis / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy; D012720:Severity of Illness Index; D016896:Treatment Outcome; D014657:Vasculitis / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy
chemical_list: D015415:Biomarkers; D007166:Immunosuppressive Agents; D018836:Inflammation Mediators; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D002097:C-Reactive Protein