Abstract 2612: Atherosclerotic Plaques Contrast-Enhanced Magnetic Resonance Imaging in Rabbits Using an Albumin-Binding Contrast Agent
Purpose : To evaluate a new blood-pool (human albumin binding) contrast-agent, B-22956, for contrast-enhanced MRI of atherosclerotic plaques in a rabbit model of atherosclerosis. Our hypothesis is that B-22956 will enhance plaques compared to the conventional Gadolinium-DTPA mainly in neo-vessel rich areas.
Methods and Results: Six atherosclerotic rabbits and 2 control rabbits underwent MRI (T1 Weighted Fast Spin Echo Sequence) on a 1.5 T system, before and up to 2 hours after Gd-DTPA (100 μmol/kg) IV injection on day one and before and up to 2 hours after B-22956 (75 μmol/kg) IV injection on day two. Mean Contrast to Noise Ratio (CNR) was measured for each plaque on axial image at different time points up to 120 mn. Changes in signal intensity were compared to the location of neo vessels studied by immunohistochemistry (anti CD 31 antibody). T1 high resolution sequences showed a highly significant plaque enhancement 2 hours after B22956 (Figure⇓) versus Gd-DTPA in the atherosclerotic group (39.75% vs 9.5%, p< 0.0001). There was no difference between the 2 compounds in the control group (15% vs 15%, p = ns). With B-22956, CNR increased linearly up to 90 mn and then reached a plateau at 120 mn. MR signal intensities 2 hours after injection of B-22956 were significantly correlated to the plaque micro-vessel density (Total number of microvessels / plaque area in mm2). Correlation r = 0.68, p = 0.003.
Conclusion: B-22956-enhanced MRI improves plaque detection compared to Gd-DTPA. The mechanism of action could be a diffusion of B-22956 from the neo-vessels into the plaque and a possible interaction with albumin and inflammation within the plaque itself.