title: Positron Emission Tomography and Magnetic Resonance Imaging of Cellular Inflammation in Patients with Abdominal Aortic Aneurysms.
abstract: OBJECTIVE
  Inflammation is critical in the pathogenesis of abdominal aortic aneurysm (AAA) disease. Combined (18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography with computed tomography (PET-CT) and ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) are non-invasive methods of assessing tissue inflammation. The aim of this study was to compare these techniques in patients with AAA.
  
  
  METHODS
  Fifteen patients with asymptomatic AAA with diameter 46 ± 7 mm underwent PET-CT with (18)F-FDG, and T2*-weighted MRI before and 24 hours after administration of USPIO. The PET-CT and MRI data were then co-registered. Standardised uptake values (SUVs) were calculated to measure (18)F-FDG activity, and USPIO uptake was determined using the change in R2*. Comparisons between the techniques were made using a quadrant analysis and a voxel-by-voxel evaluation.
  
  
  RESULTS
  When all areas of the aneurysm were evaluated, there was a modest correlation between the SUV on PET-CT and the change in R2* on USPIO-enhanced MRI (n = 70,345 voxels; r = .30; p < .0001). Although regions of increased (18)F-FDG and USPIO uptake co-localised on occasion, this was infrequent (kappa statistic 0.074; 95% CI 0.026-0.122). (18)F-FDG activity was commonly focused in the shoulder region whereas USPIO uptake was more apparent in the main body of the aneurysm. Maximum SUV was lower in patients with mural USPIO uptake.
  
  
  CONCLUSIONS
  Both (18)F-FDG PET-CT and USPIO-MRI uptake identify vascular inflammation associated with AAA. Although they demonstrate a modest correlation, there are distinct differences in the pattern and distribution of uptake, suggesting a differential detection of macrophage glycolytic and phagocytic activity respectively.
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK; Royal Infirmary of Edinburgh, Edinburgh, UK. Electronic address: olivia.mcbride@ed.ac.uk.
authors.forename: O M B
authors.initials: OM
authors.lastname: McBride
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK; Royal Infirmary of Edinburgh, Edinburgh, UK.
authors.forename: N V
authors.initials: NV
authors.lastname: Joshi
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK; Royal Infirmary of Edinburgh, Edinburgh, UK.
authors.forename: J M J
authors.initials: JM
authors.lastname: Robson
authors.affiliation: Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK.
authors.forename: T J
authors.initials: TJ
authors.lastname: MacGillivray
authors.affiliation: Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK.
authors.forename: C D
authors.initials: CD
authors.lastname: Gray
authors.affiliation: Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK.
authors.forename: A M
authors.initials: AM
authors.lastname: Fletcher
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK; Royal Infirmary of Edinburgh, Edinburgh, UK.
authors.forename: M R
authors.initials: MR
authors.lastname: Dweck
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK.
authors.forename: E J R
authors.initials: EJ
authors.lastname: van Beek
authors.affiliation: Division of Cardiovascular Medicine, University of Cambridge, Cambridge, UK.
authors.forename: J H F
authors.initials: JH
authors.lastname: Rudd
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK; Royal Infirmary of Edinburgh, Edinburgh, UK.
authors.forename: D E
authors.initials: DE
authors.lastname: Newby
authors.affiliation: Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK.
authors.forename: S I
authors.initials: SI
authors.lastname: Semple
mesh_terms: D000368:Aged; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging* / Q000473:pathology*; D017544:Aortic Aneurysm, Abdominal / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D001025:Aortitis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D001027:Aortography / Q000379:methods; D003287:Contrast Media; D003911:Dextrans; D005260:Female; D019788:Fluorodeoxyglucose F18; D006019:Glycolysis; D006801:Humans; D008264:Macrophages / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D008297:Male; D064847:Multimodal Imaging; D010587:Phagocytosis; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D019275:Radiopharmaceuticals; C097921:ferumoxtran-10; D019788:Fluorodeoxyglucose F18
keywords: Abdominal aortic aneurysms; Computed tomography; Magnetic resonance imaging; Positron emission tomography