Published in:
01-10-2010 | Head and Neck Radiology
Diffusion-weighted magnetic resonance imaging for the detection of lipid-rich necrotic core in carotid atheroma in vivo
Published in: Neuroradiology | Issue 10/2010
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Introduction
Research has shown that knowing the morphology of carotid atheroma improves current risk stratification for predicting subsequent thrombo-embolic events. Previous magnetic resonance (MR) ex vivo studies have shown that diffusion-weighted imaging (DWI) can detect lipid-rich necrotic core (LR/NC) and fibrous cap. This study aims to establish if this is achievable in vivo.
Methods
Twenty-six patients (mean age 73 years, range 54–87 years) with moderate to severe carotid stenosis confirmed on ultrasound were imaged. An echo-planar DWI sequence was performed along with standard high-resolution MR imaging. Apparent diffusion coefficient (ADC) maps were evaluated. Two independent readers reported the mean ADC values from regions of interest defining LR/NCs and fibrous caps. For subjects undergoing carotid endarterectomy (n = 19), carotid specimens were obtained and stained using Nile red.
Results
The mean ADC values were 1.0 × 10−3 mm2/s (±SD 0.3 × 10−3 mm2/s) and 0.7 × 10−3 mm2/s (±SD 0.2 × 10−3 mm2/s) for fibrous cap and LR/NC, respectively; the difference was significant (p < 0.0001). The intra-class correlation coefficients summarising the agreement between the two independent readers were 0.84 and 0.60 for fibrous cap and LR/NC, respectively. Comparison of quantitative ADC values and histology (by subjective grading of lipid content) showed a significant correlation: heavier lipid staining matched lower ADC values (r = −0.435, p = 0.005).
Conclusions
This study indicates that DWI can be used to distinguish LR/NC and the fibrous cap. The study also suggests that the mean ADC value may be linearly related to subjective graded LR/NC content determined by histology.