Ultrasonic Assessment of Myocardial Microstructure

Abstract

Echocardiography is a widely accessible imaging modality that is commonly used to non-invasively characterize and quantify changes in cardiac structure and function. Ultrasonic assessments of cardiac tissue can include analyses of backscatter signal intensity within a given region of interest. Previously established techniques have relied predominantly on the integrated or mean value of backscatter signal intensities, which may be susceptible to variability from aliased data from low frame rates and time delays for algorithms based on cyclic variation. Herein, we describe an ultrasound-based imaging algorithm that extends from previous methods, can be applied to a single image frame, and accounts for the full distribution of signal intensity values derived from a given myocardial sample. When applied to representative mouse and human imaging data, the algorithm distinguishes between subjects with and without exposure to chronic afterload resistance. The algorithm offers an enhanced surrogate measure of myocardial microstructure and can be performed using open-access image analysis software.

Ultrasonic Assessment of Myocardial Microstructure in Hypertrophic Cardiomyopathy Sarcomere Mutation Carriers With and Without Left Ventricular Hypertrophy

“…36 By contrast, the SIC utilizes grayscale values from the complete signal distribution to yield information regarding tissue microstructure, and minimizes signal reconstruction artifacts by utilizing end-diastolic B-mode frames. 9 Shifts in the signal intensity distribution, as captured by the SIC measure, appear to represent tissue level changes that can include myocardial hypertrophy, increased myocyte density, and collagen deposition. 37–41 Therefore, variation in the SIC, although measured in a pre-specified region of interest of the LV, could represent the diffuse tissue level alterations that are known to occur in HCM, such as myofibril disarray and interstitial fibrosis.…”

“…9,10 The image analysis method is applied to transthoracic echocardiographic images with the following parameters: B-mode imaging, parasternal long-axis view, end-diastolic frame, and adequate visualization of the mid-to-basal inferolateral endocardial, myocardial, and pericardial regions (Figure 1). The pericardial area directly adjacent to the mid-to-basal inferolateral myocardium (i.e.…”

“…The SIC, as a marker of myocardial microstructure, represents aggregate myocardial tissue changes following interaction of the ultrasound signal through maximum thickness of the myocardium, as previously described. 9,10 In this study, we applied the ImageJ algorithm to quantify the SIC measure on echocardiographic images for all study participants while blinded to the genotype and clinical status. Previous studies have demonstrated correlation coefficients for inter-reader and intra-reader reproducibility of SIC at 0.89 and 0.90, respectively.…”

“…Detectable variations in the resulting signal distribution can yield quantifiable differences between diseased versus healthy myocardium. 9,10 We and others have shown that ultrasound-based tissue analyses can reveal alterations in myocardial microstructure that correlate with the histologic presence of myocardial fibrosis (including both interstitial and dense replacement fibrosis) in the setting of a variety of myopathic disease processes, such as hypertensive heart disease, dilated cardiomyopathy, and post-infarct ischemic injury. 10–18 Therefore, in this pilot study, we evaluated how ultrasound-based analytical techniques compare to CMR for assessing myocardial tissue-level alterations in HCM.…”

The inappropriateness of left ventricular mass and echoreflectivity in males with essential hypertension and different CYP11B2 gene polymorphisms

“…Figure 1 demonstrates an example of such processing of the image. A more detailed description of this technique was published in [5].…”