Abstract
The purpose of this study was to characterize the alterations in microstructural organization of arterial tissue using higher-order diffusion magnetic resonance schemes. Three porcine carotid artery models namely; native, collagenase treated and decellularized, were used to estimate the contribution of collagen and smooth muscle cells (SMC) on diffusion signal attenuation using gaussian and non-gaussian schemes. The samples were imaged in a 7 T preclinical scanner. High spatial and angular resolution diffusion weighted images (DWIs) were acquired using two multi-shell (max b-value = 3000 s/mm2) acquisition protocols. The processed DWIs were fitted using monoexponential, stretched-exponential, kurtosis and bi-exponential schemes. Directionally variant and invariant microstructural parametric maps of the three artery models were obtained from the diffusion schemes. The parametric maps were used to assess the sensitivity of each diffusion scheme to collagen and SMC composition in arterial microstructural environment. The inter-model comparison showed significant differences across the considered models. The bi-exponential scheme based slow diffusion compartment (Ds) was highest in the absence of collagen, compared to native and decellularized microenvironments. In intra-model comparison, kurtosis along the radial direction was the highest. Overall, the results of this study demonstrate the efficacy of higher order dMRI schemes in mapping constituent specific alterations in arterial microstructure.
Highlights
The purpose of this study was to characterize the alterations in microstructural organization of arterial tissue using higher-order diffusion magnetic resonance schemes
It can be observed from Picrosirius red (PSR) staining of the native and collagenase treated samples that the collagen content gradually reduced after exposure to the collagenase solution over a time-period of 42 h (Fig. 1a, c—Picrosirius red)
The polarized light microscopy (PLM) images show a decrease in collagen content with increased exposure to collagenase solution (Fig. 1c, Picrosirius red)
Summary
The purpose of this study was to characterize the alterations in microstructural organization of arterial tissue using higher-order diffusion magnetic resonance schemes. Three porcine carotid artery models namely; native, collagenase treated and decellularized, were used to estimate the contribution of collagen and smooth muscle cells (SMC) on diffusion signal attenuation using gaussian and non-gaussian schemes. The parametric maps were used to assess the sensitivity of each diffusion scheme to collagen and SMC composition in arterial microstructural environment. The results of this study demonstrate the efficacy of higher order dMRI schemes in mapping constituent specific alterations in arterial microstructure. Abbreviations ADC Apparent diffusion coefficient AK Axial kurtosis CVD Cardiovascular disease dMRI Diffusion magnetic resonance imaging DKI Diffusion kurtosis imaging DTI Diffusion tensor imaging DWI Diffusion weighted image EPI Echo planar imaging FA Fractional anisotropy GAGs Glycosaminoglycans HAR High angular resolution HMb High multi b-value H&E Hematoxylin and eosin KA Kurtosis anisotropy MD Mean diffusivity. Given that collagen production from vascular cells is critical for stability, the presence of SMCs is an indication of vessel’s ability to remodel and maintain such stability[17]
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