Magnetic resonance imaging in a model of atherosclerosis: use of a collar around the rabbit carotid artery

Transverse cardiac-cycle gated high resolution magnetic resonance images have been obtained from the neck of the New Zealand white rabbit both in normal animals and from those in which a collar had been earlier positioned around one carotid artery. The study included animals fed on normal and on high cholesterol diets with the surgical modification having been demonstrated previously to cause a rapid and reproducible lesion resembling early atherosclerosis. The aim of the work was to investigate the attainable spatial resolution and sensitivity at a field strength of 2 T using a large radiofrequency transmitter system and a surface coil receiver with which spin-echo images have been obtained. Visualization was enhanced using a three-dimensional interpolation technique. An image resolution of 200 microns was readily obtained but was shown to be insufficient for delineating pathological features within the artery wall such as intimal layer thickening. The results have been compared with histopathological findings which confirmed that any morphological changes were within the pixel resolution of the image. Extensions to the methodology are proposed which should be able to detect atherosclerotic changes with a resolution of 50 microns within a feasible imaging time. In addition, the MRI study of how the surgical intervention alters the artery shape and curvature was carried out and the MRI demonstrated that collar implantation in general does not occlude the artery and causes only a slight and gradual degree of curvature to the vessel.