MRI of early- and late-stage arterial remodeling in a low-level cholesterol-fed rabbit model of atherosclerosis

Purpose: To monitor early- and late-stage arterial remodeling following low-level cholesterol (CH) feeding in rabbits using a standardized MRI protocol. Materials and Methods: New Zealand White rabbits were fed a CH diet (0.25% w/w) (n = 15) or normal chow (n = 6) and imaged either at 0, 2, 6, 8, and 11 months ("early-stage") or 12, 14, 16, 18, and 20 months ("late-stage"). T2-weighted fast-spin-echo images (approximate to 200 mu m in-plane resolution) of aortic lesions were collected using either a 1.5 or 3.0T MR scanner interfaced with a customized surface RF coil. Luminal (LA), outer vessel wall boundary (OVBA), and vessel wall areas (VWA) were assessed. Results: Among CH-fed animals in the early-stage group, increased VWA associated with decreased OVBA and a more pronounced decrease in LA was first detectable at 8 months. These changes became more evident between 8 and 11 months. In the late-stage group, lesions continued to grow in response to CH-feeding, as VWA significantly increased at regular 2-month intervals. Beyond 16 months, signal intensity differences (reflecting increased lesion complexity) within the vessel wall were noted. Conclusion: This often-overlooked rabbit model combined with customized MR technology holds tremendous promise for studying the natural progression, regression, and remodeling of atherosclerotic lesions.