title: Detection and quantification of large-vessel inflammation with 11C-(R)-PK11195 PET/CT.
abstract: We investigated whether PET/CT angiography using 11C-(R)-PK11195, a selective ligand for the translocator protein (18 kDa) expressed in activated macrophages, could allow imaging and quantification of arterial wall inflammation in patients with large-vessel vasculitis.
  
  
  METHODS
  Seven patients with systemic inflammatory disorders (3 symptomatic patients with clinical suspicion of active vasculitis and 4 asymptomatic patients) underwent PET with 11C-(R)-PK11195 and CT angiography to colocalize arterial wall uptake of 11C-(R)-PK11195. Tissue regions of interest were defined in bone marrow, lung parenchyma, wall of the ascending aorta, aortic arch, and descending aorta. Blood-derived and image-derived input functions (IFs) were generated. A reversible 1-tissue compartment with 2 kinetic rate constants and a fractional blood volume term were used to fit the time-activity curves to calculate total volume of distribution (VT). The correlation between VT and standardized uptake values was assessed.
  
  
  RESULTS
  VT was significantly higher in symptomatic than in asymptomatic patients using both image-derived total plasma IF (0.55±0.15 vs. 0.27±0.12, P=0.009) and image-derived parent plasma IF (1.40±0.50 vs. 0.58±0.25, P=0.018). A good correlation was observed between VT and standardized uptake value (R=0.79; P=0.03).
  
  
  CONCLUSIONS
  11C-(R)-PK11195 imaging allows visualization of macrophage infiltration in inflamed arterial walls. Tracer uptake can be quantified with image-derived IF without the need for metabolite corrections and evaluated semiquantitatively with standardized uptake values.
authors.affiliation: MRC Clinical Sciences Centre and National Heart and Lung Institute, Imperial College, Hammersmith Campus, and GE Imanet, Hammersmith Hospital, London, United Kingdom.
authors.forename: Frederic
authors.initials: F
authors.lastname: Lamare
authors.forename: Rainer
authors.initials: R
authors.lastname: Hinz
authors.forename: Oliver
authors.initials: O
authors.lastname: Gaemperli
authors.forename: Francesca
authors.initials: F
authors.lastname: Pugliese
authors.forename: Justin C
authors.initials: JC
authors.lastname: Mason
authors.forename: Terence
authors.initials: T
authors.lastname: Spinks
authors.forename: Paolo G
authors.initials: PG
authors.lastname: Camici
authors.forename: Ornella E
authors.initials: OE
authors.lastname: Rimoldi
mesh_terms: D000328:Adult; D000368:Aged; D002250:Carbon Radioisotopes; D006801:Humans; D007546:Isoquinolines / Q000378:metabolism*; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014657:Vasculitis / Q000175:diagnosis*
chemical_list: D002250:Carbon Radioisotopes; D007546:Isoquinolines; C037850:PK 11195