Paramagnetic contrast enhancement of coronary atherosclerotic lesions in ECG-gated study of the heart by using open MRI-scanners

The aim of the study was to evaluate the capabilities of contrast-enhanced magnetic resonance imaging (MRI) with the use of open MRI scanners for detection of atherosclerotic plaques in patients with extensive atherosclerosis and myocardial infarction which occurred two to six months prior the examination. Twenty four patients with angiologically verified coronary atherosclerosis comprised the patient’s group including 11 patients with predominant involvement of right coronary artery (RCA) and 13 patients with predominant atherosclerosis of left circumflex coronary artery. All patients received contrast-enhanced MRI study of the heart by using T1-weighted spin-echo with end-diastolic ECG gating (MRI scanners AZ-360 with 0.38T field and Magnetom Open with 0.22T) Thin 7-8-mm axial slices of the whole heart were obtained in four-chamber position in all patients; short axis slices were obtained in 16 out of 24 patients. Acquisition parameters were as follows: repetition time (TR) of 450-890 ms; echo time (ET) of 15-25 ms; 256х256 matrix; slice thickness of 7-8 mm; cross-dimension field of view of 25х25 cm; and voxel size of 0.1 to 0.12 mm. Paramagnetic (Optimark, Mallinckrodt Inc.) was injected as 2 mL of 0.5-M solution per 10 kg of body weight. For the atherosclerotic plaque itself and arterial wall beyond the plaque, the index of image enhancement (IE) was calculated as follows: IE = intensity of T1 w SE scan with paramagnetic / Intensity of T1 w sE scan initial. When analyzed visually, the T1-weighted contrast-enhanced MRI images in patients with coronary atherosclerosis provided clear delineation of coronary artery stenosis due to the significant uptake of paramagnetic by the plaque itself. In patients from the control group free of atherosclerosis, the RCA IE and LCA IE were 1.08+0.06 and 1.09±0.07, respectively. The atherosclerotic plaque in infarction-related LCA demonstrated IE as high as 1.52+0.23, whereas the plaque in infarction-related RCA was enhanced with IE=1.43±0.17. Also, the plaque-free areas of infarction-related arteries demonstrated mild but elevated enhancement with IE=1.18+0.10. In this small group, no significant correlations were revealed between IE and degree of stenosis or LV contractility indices. The authors conclude that contrast-enhanced MRI of coronary atherosclerotic plaques is recommended as an addition to inversion recovery protocol that provides effective imaging of paramagnetic uptake by damaged myocardium.