Optimization of ex vivo CT- and MR- imaging of atherosclerotic vessel wall changes.

Objective: To optimize a methodology for ex vivo imaging of atherosclerotic vessel wall changes using multidetector-row computed tomography (MDCT) and multi-contrast magnetic resonance imaging (MRI).

Methods: In phantom studies and studies on intact ex vivo porcine and human hearts, various filling mixtures of MDCT and MRI contrast agents have been evaluated, to enable filling and distension of the coronary arteries for optimal visualization of atherosclerotic vessel wall changes with both techniques. Various proportions of methyl cellulose, iodine-containing CT contrast agent and paramagnetic MR contrast agent containing iron-oxide particles have been tested. Imaging parameters have been optimized for high resolution plaque imaging using a four detector-row CT scanner and a 1.5 T MR system.

Results: Phantom studies and studies on ex vivo porcine and human hearts demonstrated optimal proportion of methyl cellulose and CT contrast agent to be 98% vs. 2%, and 75% vs. 25% of methyl cellulose vs. MR contrast agent, respectively. These proportions provided optimal opacification of the vessel lumen in the MDCT images with 250 Hounsfield Units, and good signal suppression within the vessel lumen in the MR images, resembling in vivo imaging techniques. After retrospective matching with histopathology, atherosclerotic lesions of the human ex vivo specimens could be identified on MRI and MDCT images.

Conclusion: Using an optimized mixture of methyl cellulose, MDCT and MRI contrast agents, visualization of atherosclerotic vessel wall changes is feasible, and applicable to various ex vivo models.