Bimodal Thrombus Imaging: Simultaneous PET/MR Imaging with a Fibrin-targeted Dual PET/MR Probe-Feasibility Study in Rat Model

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.
Radiology (Impact Factor: 6.87). 03/2011; 258(3):812-20. DOI: 10.1148/radiol.10100881
Source: PubMed


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.
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.
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.
A fibrin-targeted dual PET/MR probe enables simultaneous, direct MR and PET imaging of thrombus.

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    • "EP-2104R is a Gd-based MR imaging agent functionalized with a short peptide with high affinity to fibrin 173-175. A novel 64Cu labeled EP-2104R showed promising results in depicting arterial thrombi by hybrid MR-PET in a rat model 176. Quantification of intraplaque and endothelial fibrin has been achieved by applying novel T1 mapping techniques of the injected EP2104R 177. "
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