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Abstract #4208

Nuclear Magnetic Relaxation Dispersion Studies of MR Sensor Agents for Myeloperoxidase Imaging

Yuanxin Chen1, John A. Ronald2, Elisenda Rodriguez3, John W. Chen3, Kem A. Rogers4, Brian K. Rutt2

1Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada; 2Department of Radiology, Stanford University, Stanford, CA, United States; 3Center for Systems Biology and Department of Radiology, Massachusetts General Hospital, Boston, United States; 4Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada

Bis-5-hydroxytryptamide-diethylenetriamine-pentaacetate gadolinium [bis-5HT-DTPA(Gd)] is a highly sensitive and specific magnetic resonance reporter of myeloperoxidase (MPO) activity in vivo. In this study, we measured water proton T1 nuclear magnetic relaxation dispersion (NMRD) profiles for bis-5HT-DTPA(Gd) solutions and of the aortic specimen excised from atherosclerotic rabbits 2 hours after injection of bis-5HT-DTPA(Gd). When activated by MPO, bis-5HT-DTPA(Gd) exhibits a significant relaxivity increase over the entire range of magnetic fields up to 0.93 T. Similarly, the NMRD profiles of atherosclerotic aorta showed increased relaxivity enhancement compared to aortic specimen from control rabbits. This supports our in vivo MRI results that bis-5HT-DTPA(Gd) targets of MPO and identifies active inflammation in experimental atherosclerosis.