title: Bimodal thrombus imaging: simultaneous PET/MR imaging with a fibrin-targeted dual PET/MR probe--feasibility study in rat model.
abstract: OBJECTIVE
  To image thrombus by using magnetic resonance (MR) imaging and positron emission tomography (PET) simultaneously in a rat arterial thrombus model with a dual PET/MR probe.
  
  
  METHODS
  Animal studies were approved by the institutional animal use committee. A dual PET/MR probe was synthesized by means of partial exchange of gadolinium for copper 64 ((64)Cu) in the fibrin-targeted MR probe EP-2104R. A preformed 25-mm thrombus was injected into the right internal carotid artery of a rat. Imaging was performed with a clinical 3.0-T MR imager with an MR-compatible human PET imager. Rats (n = 5) were imaged prior to and after systemic administration of the dual probe by using simultaneous PET/MR. The organ distribution of (64)Cu and gadolinium was determined ex vivo (n = 8), 2 hours after injection by using well counting and inductively coupled plasma mass spectrometry, respectively. Signal intensity ratios (SIRs) between the thrombus-containing and contralateral vessel were computed from PET images and MR data before and after probe administration.
  
  
  RESULTS
  The dual probe was synthesized with greater than 98% radiochemical purity. Thrombus enhancement was observed in all five animals at both MR (SIR([postprobe])/SIR([preprobe]) = 1.71 ± 0.35, P = .0053) and PET (SIR = 1.85 ± 0.48, P = .0087) after injection of the dual PET/MR probe. Ex vivo analysis at 2 hours after injection showed the highest (64)Cu and gadolinium concentrations, after the excretory organs (kidney and liver), to be in the thrombus.
  
  
  CONCLUSIONS
  A fibrin-targeted dual PET/MR probe enables simultaneous, direct MR and PET imaging of thrombus.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129, USA.
authors.forename: Ritika
authors.initials: R
authors.lastname: Uppal
authors.forename: Ciprian
authors.initials: C
authors.lastname: Catana
authors.forename: Ilknur
authors.initials: I
authors.lastname: Ay
authors.forename: Thomas
authors.initials: T
authors.lastname: Benner
authors.forename: A Gregory
authors.initials: AG
authors.lastname: Sorensen
authors.forename: Peter
authors.initials: P
authors.lastname: Caravan
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003287:Contrast Media; D005240:Feasibility Studies; D005337:Fibrin; D005682:Gadolinium; D006571:Heterocyclic Compounds; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013058:Mass Spectrometry; D009942:Organometallic Compounds; D010455:Peptides; D049268:Positron-Emission Tomography / Q000379:methods*; D051381:Rats; D013927:Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging
chemical_list: D003287:Contrast Media; C503783:EP-2104R; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D010455:Peptides; D005337:Fibrin; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate; D005682:Gadolinium