Introduction:Grayscale (GS) texture features that examine homogeneity and echogenicity have been used to identify vulnerable plaques with in vivoultrasound imaging have been shown to correlate with plaque tissue composition. However, the relationship of collagen fiber organization to GS texture features extracted from in vivoimages is a novel idea to provide additional information about plaque structure. We hypothesize that collagen fiber alignment is clinically relevant to identify vulnerable plaques. The objective of this feasibility study was to use multiscale imaging (in vivo ultrasound and high resolution optical microscopy) to determine how GS texture features are related to plaque collagen structure.Methods:Participants (n=6) scheduled for clinically indicated carotid endarterectomy underwent in vivocarotid ultrasound imaging with texture feature extraction (spatial gray level dependence matrices method for calculating angular second moment [SGLDM-ASM] and grayscale median value [GSM]). Plaque specimens were sent to histopathology and stained with H&E. The collagen fibers in the fibrous cap of the plaque histopathology slides were imaged with liquid crystal based polarization microscopy and quantified using an established software tool (CurveAlign). Correlations between collagen alignment coefficient (range 0-1, 1 represents perfectly aligned fibers) and the texture feature SGLDM-ASM (a measure of homogeneity, higher values are more homogenous) and GSM (a measure of echogenicity higher values are more echogenic) were examined.Results:Participants were mean (SD) 72.5 (6.1) years of age, had 71.67 (8.16) percent stenosis. The mean SGLDM-ASM was 0.0017 (0.0023), the mean SD GSM was 73.13 (30.98). SGLDM-ASM was significantly correlated to collagen alignment (r=0.83; p=0.028). There was no significant correlation detected between GSM and collagen alignment (r=-0.43;p=0.38).Conclusion:Results of this study indicate the potential role for using high resolution optical microscopy with ultrasound to characterize collagen fiber alignment in plaques with measures of homogeneity. Future studies are needed to see how multiscale imaging can be used to inform in vivoimaging for identification of vulnerable plaque features.