Detection of thrombus size and protein content by ex vivo magnetization transfer and diffusion weighted MRI

Background: to utilize a rabbit model of plaque disruption to assess the accuracy of different magnetic resonance sequences [t1-weighted (t1w),t2-weighted (t2w),magnetization transfer (mt) and diffusion weighting (dw)] at 11.7 t for the ex vivo detection of size and composition of thrombus associated with disrupted plaques. methods: atherosclerosis was induced in the aorta of male new zealand white rabbits (n = 17) by endothelial denudation and high-cholesterol diet. subsequently,plaque disruption was induced by pharmacological triggering. segments of infra-renal aorta were excised fixed in formalin and examined by ex vivo magnetic resonance imaging (mri) at 11.7 t and histology. results: mri at 11.7 t showed that: (i) magnetization transfer contrast (mtc) and diffusion weighted images (dwi) detected thrombus with higher sensitivity compared to t1w and t2w images [sensitivity: mtc = 88.2%,dwi = 76.5%,t1w = 66.6% and t2w = 43.7%,p≥0.001]. similarly,the contrast-to-noise (cnr) between the thrombus and the underlying plaque was superior on the mtc and dwi images [cnr: mtc = 8.5 ± 1.1,dwi = 6.0 ± 0.8,t1w = 1.8 ± 0.5,t2w = 3.0 ± 1.0,p≥0.001]; (ii) mtc and dwi provided a more accurate detection of thrombus area with histology as the gold-standard [underestimation of 6% (mtc) and 17.6% (dwi) compared to an overestimation of thrombus area of 53.7% and 46.4% on t1w and t2w images,respectively]; (iii) the percent magnetization transfer rate (mtr) correlated with the fibrin (r = 0.73,p = 0.003) and collagen (r = 0.9,p = 0.004) content of the thrombus. conclusions: the conspicuity of the thrombus was increased on mtc and dw compared to t1w and t2w images. changes in the %mtr and apparent diffusion coefficient can be used to identify the organization stage of the thrombus. © 2012 phinikaridou et al.; licensee biomed central ltd.