Atherosclerosis is the primary cause of morbidity and mortality. Conventional imaging of atherosclerotic plaque has been limited to external morphology and localization of calcification. MR imaging and spectroscopy may allow the study the biochemical components of plaque in vivo. Many plaque components have very short T2 relaxation times, preventing routine imaging. A rapid """"""""projection-reconstruction"""""""" sequence with TE=0.2 ms and suppression of long T2 species has been developed. We used it in vitro to study unfixed autopsy specimens (abdominal aorta) andin vivo to image carotid grafts in dogs fed atherogenic diets. Methods and Results Fresh infrarenal human aortas were obtained at autopsy and imaged in a perfiubron bath using routine sequences and the short TE projection reconstruction sequences. The specimens were then analyzed pathologically. Non-atheromatous abdominal aortic specimen consisted of inner thin endothelial tunica intima, a muscular tunica media with interspersed elastin fibers and a tunica adventitia consisting of connective tissue and small nutrient vessels. Atherosclerotic changes occurred primarily in the intima, with the development of a thickened fibrous cap overlying varying amounts of underlying cholesterol crystals and lipid laden macrophages. Calcification occurred beneath the fibrous cap. Hemosiderin laden macrophages collected in regions of focal hemorrhage. The media thinned to varying degrees. In FSE images, the adventitia is relatively high in signal, the media low, and the atherosclerotic plaque irregular. Very low signal areas correspond to calcification, and cause BO inhomogeneity, as seen in 3-point Dixon images. Discussion Novel MR techniques are able to image intima, media, and adventitia, and demonstrate calcium, and fibrous and lipid components of plaque. Hemoglobin degradation products should be visible as peak shifts, but were not observed in these specimens. Demonstration and analysis of plaque components. should lead to better understanding of atherogenesis, medical treatment monitoring, and surgical planning.
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