In vivo and ex vivo measurements of the mean ADC values of lipid necrotic core and hemorrhage obtained from diffusion weighted imaging in human atherosclerotic plaques

Abstract

Purpose: To determine the apparent diffusion coefficient (ADC) values of lipid and hemorrhage in atherosclerotic plaque in human carotid arteries in vivo and compare the values obtained from ex vivo carotid endarterectomy specimens. Materials and Methods:In vivo diffusion-weighted imaging (DWI) of carotid plaques was performed using a 2D single shot Interleaved Multislice Inner Volume Diffusion Weighted Echo Planar Imaging (2D ss-IMIV DWEPI) on 8 subjects who subsequently underwent carotid endarterectomy. A total of 32 slices used to construct the ADC maps were reviewed for the measurement of the mean ADC values in vessel wall, hemorrhage, and lipid necrotic core. The 8 endarterectomy specimens were scanned using by three-dimensional ms-IV-DWEPI. After the ADC maps were created, the mean ADC values in the same locations selected for in vivo values were calculated.

In Vivo Magnetization Transfer and Diffusion-Weighted Magnetic Resonance Imaging Detects Thrombus Composition in a Mouse Model of Deep Vein Thrombosis

“…The ADC values of organized hemorrhage in carotid plaque in vivo were characterized by the most restricted diffusion, whereas the lysed thrombus showed increased diffusivity. 34 Similarly, we found that the most restricted water diffusion was observed within the erythrocyte-rich (day 1) and collagen-rich (days 21 and 28) thrombus. However, the mechanism causing restricted water diffusion in erythrocyte-rich and collagen-rich thrombus may be different.…”

“…42,44 Moreover, several other mechanisms contribute to the degree of MT, including the mobility, the hydration state, and the number of hydroxyl and amide groups, 43 as well as the concentration of the macromolecules or water. 46 DWI has been used ex vivo to identify thrombus in human [32][33][34] and animal 30,31 samples. In vivo application of DWI in human carotid plaque showed that changes in the ADC, which represent the magnitude of diffusion of water molecules, vary in parallel to the evolution of thrombus organization.…”

“…In vivo MT has been used to detect intracranial hemorrhage, 26,27 and ex vivo magnetization transfer contrast (MTC) showed the feasibility of visualizing regions of organized proteins in atherosclerosis 28,29 and thrombus associated with plaque rupture. 30 DW imaging (DWI) detected thrombus, [31][32][33][34] and calculation of the apparent diffusion coefficient (ADC) in vitro reflected the stages of thrombus aging and organization. 35 The protein content of thrombus and the diffusivity of water molecules depend on the local tissue microenvironment.…”

MRI of Carotid Atherosclerosis

“…Diffusion-weighted imaging of atherosclerosis yields quantitative estimates of the apparent diffusion coefficients, which have been found to be substantially lower in lipid rich cores compared with normal vessel wall or IPH [41]. Susceptibility-weighted imaging has been applied to peripheral arteries and found to have high accuracy for the detection of calcifications [42].…”

Imaging diseases of the aorta by MRI: a cost-effectiveness analysis of contrast-enhanced studies compared to non-contrast enhanced angiographic studies

“…DWI has been shown to detect thrombus [18,32-35], and MT could be a promising, yet unexplored, approach to detect regions of organized proteins [36,37]. Because of the protein content of thrombus and the differences in the diffusivity of water molecules depending on the local microenvironments, we hypothesized that MT and DWI could be used to generate endogenous contrast for imaging thrombus without the need of targeted agents.…”