Name: ultrasonic assessment of myocardial microstructure
Uploaded: 2014-01-14T13:00:00
Description: Watch this Scientific Journal Video about Ultrasonic Assessment of Myocardial Microstructure at JoVE.com

We are grateful for resources provided by the Harvard Medical School/Brigham and Women&#39;s Hospital Cardiovascular Physiology Core Laboratory. This work was supported in part by funding from the National Institutes of Health grants HL088533, HL071775, HL093148, and HL099073 (RL). MB was a recipient of an American Heart Association founder affiliate postdoctoral fellowship award. KU is a recipient of an American Heart Association founders affiliate postdoctoral fellowship award. SC was supported by an award from the Ellison Foundation.

1. Preparation of Images for Analyses
<ol>
	<li>Obtain murine or human echocardiographic B-mode images in the parasternal long-axis view. Adjust time-gain compensation settings and placement of the transmit focus to optimize visualization of the LV and other cardiac structures in the parasternal view, per usual practice. Ensure all images are saved in DICOM file format. Standardized image views place the inferolateral left ventricular wall at the base of the frame. Frames must display the entirety of the left ventricul...

<ol>
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We describe the protocol for an image analysis algorithm that quantifies sonographic signal intensity distribution and, in turn, offers a surrogate measure of myocardial microstructure. Standardized features of the protocol, including selection, sizing, and positioning of the ROI and reference region, serve to minimize user- and subject-based variability. We demonstrate that when applied to end-diastolic single-frame echocardiographic images, the algorithm can appropriately distinguish between normal myocardium versus my...

Echocardiography is a widely accessible imaging modality that is commonly used to noninvasively 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 at a single point in time, as well as over the course of the cardiac cycle. Prior studies have suggested that measures of sonographic signal intensity can identify the underlying presence of myocardial fiber disarray, viable versus nonviable myocardial tissue, and interstitial fibrosis1-3. We refer to myocardial &#8216;microstructure&#8217; as the tissue architecture that can be characterized, using sonographic analysis, beyond linear measurements of gross size and morphology. Accordingly, analyses of sonographic signal intensity have been used to evaluate microstructural alterations of myocardial tissue in the setting of hypertrophic and dilated cardiomyopathy4,5, chronic coronary artery disease6,7, and hypertensive heart disease8,9.&#160;However, previously established techniques have relied predominantly on the integrated or mean value of backscatter signal intensities, which may be susceptible to variability from random noise5, aliased data from low frame rates10, and time delays for algorithms based on cyclic variation11.
Herein, we describe the method of using an ultrasound-based image analysis algorithm that extends from previous methods; this algorithm focuses on a single end-diastolic frame for image analysis and accounts for the full distribution of signal intensity values derived from a given myocardial sample. By using the pericardium as an in-frame reference12,13, the algorithm reproducibly quantifies variation in sonographic signal intensity distributions and offers an enhanced surrogate measure of myocardial microstructure. In a step-by-step protocol, we describe methods for preparing images for use, sampling regions of interest, and processing data within selected regions of interest. We also show representative results from applying the algorithm to echocardiographic images acquired from mice and humans with variable exposure to afterload stress on the left ventricle.

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			<td height="21" style="height:21px;width:216px;">ImageJ v 1.46</td>
			<td style="width:268px;">NIH (Bethesda, MD)</td>
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			<td style="width:167px;">open access software</td>
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			<td height="21" style="height:21px;">Power ShowCase</td>
			<td style="width:268px;">Trillium Technology (Ann Arbor, MI)</td>
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			<td>commercial software</td>
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ultrasonic assessment of myocardial microstructure

Echocardiography is a widely accessible imaging modality that is commonly used to noninvasively 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&#160;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.

Signal intensity analysis is performed in 4 main steps (Figure 1), including: 1) image selection and formatting, 2) sampling ROI and reference areas, 3) algorithm application, and 4) processing final values to yield myocardial-to-pericardial intensity ratios. Selection and size of the ROI is standardized to limit interuser as well as intrauser variability (Figure 2). The positioning of each ROI is also standardized with respect to each subject&#39;s anatomical structures to limit intersu...

Watch this Scientific Journal Video about Ultrasonic Assessment of Myocardial Microstructure at JoVE.com

Ultrasonic Assessment of Myocardial Microstructure

Echocardiography is commonly used to noninvasively characterize and quantify changes in cardiac structure and function. We describe an ultrasound-based imaging algorithm that offers an enhanced surrogate measure of myocardial microstructure and can be performed using open-access image analysis software.

Echocardiography is a widely accessible imaging modality that is commonly used to noninvasively characterize and quantify changes in cardiac structure and ...

Research

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