title: (18)F-FDG PET/MRI evaluation of retroperitoneal fibrosis: a simultaneous multiparametric approach for diagnosing active disease.
abstract: OBJECTIVE
  The aim of this study was to evaluate integrated (18)F-FDG PET/MRI as a one-stop diagnostic procedure in the assessment of (active) idiopathic retroperitoneal fibrosis (RPF) METHODS: A total of 22 examinations comprising a PET/CT scan followed by a PET/MRI scan in 17 patients (13 men, 4 women, age 58 ± 11 years) with histopathologically confirmed RPF at diagnosis or during follow-up under steroid therapy were analysed in correlation with laboratory inflammation markers (ESR, CRP). The patient cohort was subdivided into two groups: 6 examinations in untreated and 16 in treated patients. Tissue formations in typically periaortic localization suggestive of RPF were visually and quantitatively evaluated. The PET analysis included the assessment of SUVmax and a qualitative score for FDG uptake in RPF tissue in relation to the uptake in the liver. MRI analysis included evaluation of the T2-weighted image signal intensity, contrast enhancement and diffusion restriction (ADC values). Mean values were compared using the Mann-Whitney U test. ADC, SUVmax and ESR values were correlated using Pearson's correlation.
  
  
  RESULTS
  MRI analysis revealed restricted diffusion in 100 % and 56 %, hyperintense T2 signal in 100 % and 31 %, and contrast enhancement in the periaortic tissue formation suggestive of RPF in 100 % and 62.5 % in the untreated and treated patients, respectively. In the qualitative and quantitative PET analysis, statistically significant differences were found for mean FDG uptake scores (2.5 ± 0.8 in untreated patients and 1.1 ± 0.9 in treated patients) and mean SUVmax (7.8 ± 3.5 and 4.1 ± 2.2, respectively). A strong correlation was found between the ADC values and SUVmax (Pearson r   -0.65, P = 0.0019), and between ESR and CRP values and SUVmax (both r = 0.45, P = 0.061).
  
  
  CONCLUSIONS
  Integrated (18)F-FDG PET/MRI shows high diagnostic potential as a one-stop diagnostic procedure for the assessment of (active) RPF providing multiparametric supportive information.
authors.affiliation: Department of Nuclear Medicine, Medical Faculty, University Duisburg-Essen, University Hospital Essen, Hufelandstraße 55, 45147, Essen, Germany. verena.ruhlmann@uk-essen.de.
authors.forename: Verena
authors.initials: V
authors.lastname: Ruhlmann
authors.affiliation: Department of Nuclear Medicine, Medical Faculty, University Duisburg-Essen, University Hospital Essen, Hufelandstraße 55, 45147, Essen, Germany.
authors.forename: Thorsten Dirk
authors.initials: TD
authors.lastname: Poeppel
authors.affiliation: Department of Urology and Paediatric Urology, HELIOS Medical Center Wuppertal, University Hospital Witten/Herdecke, Heusnerstr. 40, 42283, Wuppertal, Germany.
authors.forename: Alexander Sascha
authors.initials: AS
authors.lastname: Brandt
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Hufelandstraße 55, 45122, Essen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Grüneisen
authors.affiliation: Department of Nuclear Medicine, Medical Faculty, University Duisburg-Essen, University Hospital Essen, Hufelandstraße 55, 45147, Essen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Ruhlmann
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Hufelandstraße 55, 45122, Essen, Germany.
authors.forename: Jens Matthias
authors.initials: JM
authors.lastname: Theysohn
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Hufelandstraße 55, 45122, Essen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Forsting
authors.affiliation: Department of Nuclear Medicine, Medical Faculty, University Duisburg-Essen, University Hospital Essen, Hufelandstraße 55, 45147, Essen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bockisch
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Hufelandstraße 55, 45122, Essen, Germany.
authors.forename: Lale
authors.initials: L
authors.lastname: Umutlu
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D012185:Retroperitoneal Fibrosis / Q000000981:diagnostic imaging* / Q000628:therapy
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: Multiparametric; One-stop diagnostic procedure; PET/MRI; Retroperitoneal fibrosis