Characterization of aortic root atherosclerosis in ApoE knockout mice: High‐resolution in vivo and ex vivo MRM with histological correlation

Abstract

In vivo, cardiac-gated, black-blood, and ex vivo magnetic resonance microscopy (MRM) images of the aortic root, and histopathology data were obtained from 12 transgenic and wildtype (WT) mice. MRM was performed using a black-blood imaging spin-echo sequence with upstream and downstream inflow saturation pulses to obtain aortic root images in three contrast techniques: proton density-weighted (PDW), T 1 -(T 1 W), and T 2 -weighted (T 2 W). Aortic wall thickness and area were measured and correlated with histopathology data (R > 0.90). Ex vivo lesion components (lipid core, fibrous tissue, and cell tissue) were identified and characterized by differing image contrast in PDW, T 1 W, and T 2 W MRM, and by histopathology. The differences between WT and transgenic mice for maximal wall thickness and area were statistically significant (P < 0.05). This study demonstrates the feasibility of in vivo murine aortic root lesion assessment and ex vivo plaque characterization by MRM. Magn Reson Med 49:381-385, 2003.

Serial Studies of Mouse Atherosclerosis by In Vivo Magnetic Resonance Imaging Detect Lesion Regression After Correction of Dyslipidemia

“…We recently reported imaging the aortic root, but those measurements were limited to ex vivo analysis. 26 In the present study, we have shown that diet-induced spontaneous lesion development can be studied if the appropriate imaging method is used to avoid the respiratory and cardiac motion.We 13 and others 40 have noted that MR measurements of arterial wall parameters are exaggerated compared with those obtained by histopathology, an effect likely caused by tissue shrinkage during the fixation and paraffin-embedding process or to anatomic misalignment of MR and histopathology sections. To circumvent this latter difficulty, we have used an alternative strategy by calculating the total lesion volume (ie, burden) in the atherosclerotic graft by obtaining serial in vivo MR images and ex vivo histological sections throughout the entire aortic arch.…”

“…A combined parametric (colored) MR image was obtained by superimposing images in Figure 5A through 5C with red, green, and blue channels assigned to each image, respectively, as described. 26 The resulting parametric image has a spatial distribution according to the type of tissue present in the specimen, with lipid areas appearing red (T 1 W contribution) and collagen as green (PDW contribution). …”

Validation of Automatically Classified Magnetic Resonance Images for Carotid Plaque Compositional Analysis

“…12,14,19 However, these studies analyzed atherosclerotic plaques in quadrants, and the simple presence or absence of the plaque components was then assessed with MRI. Such methodology does not evaluate the ability of MR to precisely determine the spatial location and size of plaque components.…”

“…This set has often been used in other studies. 11,12 The overall accuracies for each of the 3 conditions were compared with a paired t test. For this purpose, data from cross-sections extracted from the same endarterectomy specimen were combined to ensure that the t statistic was calculated using truly independent samples (nϭ13 endarterectomy specimens), a requirement for the t test.…”

Dynamic changes in murine vessel geometry assessed by high‐resolution magnetic resonance angiography: A 9.4T study

“…In contrast to previous studies that focused on lesion detection by visualization of the vessel wall with twodimensional black-blood methods (11)(12)(13)(14)(15)(16)(17)(18), this work presents a different approach: in order to be able to sensitively detect changes in vessel lumina in pathologic mouse models, we implemented a fast, brightblood, three-dimensional MR method. Because of the method's temporally varying T1-reducing effect, and to avoid toxic side effects (19,20), we did not use any contrast agent.…”