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Pittman LA, Whittaker P, Milne ML, Chung CS. Collagenase treatment reduces the anisotropy of ultrasonic backscatter in rat myocardium by reducing collagen crosslinks. Physiol Rep 2023; 11:e15849. [PMID: 37960992 PMCID: PMC10643982 DOI: 10.14814/phy2.15849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 10/19/2023] [Accepted: 10/19/2023] [Indexed: 11/15/2023] Open
Abstract
Dysregulation of collagen deposition, degradation, and crosslinking in the heart occur in response to increased physiological stress. Collagen content has been associated with ultrasonic backscatter (brightness), and we have shown that the anisotropy of backscatter can be used to measure myofiber alignment, that is, variation in the brightness of a left ventricular short-axis ultrasound. This study investigated collagen's role in anisotropy of ultrasonic backscatter; female Sprague-Dawley rat hearts were treated with a collagenase-containing solution, for either 10 or 30 min, or control solution for 30 min. Serial ultrasound images were acquired at 2.5-min intervals throughout collagenase treatment. Ultrasonic backscatter was assessed from anterior and posterior walls, where collagen fibrils are predominately aligned perpendicular to the angle of insonification, and the lateral and septal walls, where collagen is predominately aligned parallel to the angle of insonification. Collagenase digestion reduced backscatter anisotropy within the myocardium. Collagen remains present in the myocardium throughout collagenase treatment, but crosslinking is altered within 10 min. These data suggest that crosslinking of collagen modulates the anisotropy of ultrasonic backscatter. An Anisotropy Index, derived from differences in backscatter from parallel and perpendicularly aligned fibers, may provide a noninvasive index to monitor the progression and state of myocardial fibrosis.
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Affiliation(s)
| | | | - Michelle L. Milne
- Department of PhysicsSt Mary's College of MarylandSt Mary's CityMarylandUSA
| | - Charles S. Chung
- Department of PhysiologyWayne State UniversityDetroitMichiganUSA
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Milne ML, Schick BM, Alkhazal T, Chung CS. Myocardial Fiber Mapping of Rat Hearts, Using Apparent Backscatter, with Histologic Validation. ULTRASOUND IN MEDICINE & BIOLOGY 2019; 45:2075-2085. [PMID: 31155403 PMCID: PMC6615029 DOI: 10.1016/j.ultrasmedbio.2019.05.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/26/2019] [Accepted: 05/06/2019] [Indexed: 06/09/2023]
Abstract
Myocardial fiber architecture is a physiologically important regulator of ejection fraction, strain and pressure development. Apparent ultrasonic backscatter has been shown to be a useful method for recreating the myocardial fiber architecture in human-sized sheep hearts because of the dependence of its amplitude on the relative orientation of a myofiber to the angle of ultrasonic insonification. Thus, the anisotropy of the backscatter signal is linked to and provides information about the fiber orientation. In this study, we sought to determine whether apparent backscatter could be used to measure myofiber orientation in rodent hearts. Fixed adult-rat hearts were imaged intact, and both a transmural cylindrical core and transmural wedge of the left ventricular free wall were imaged. Cylindrical core samples confirmed that backscatter anisotropy could be measured in rat hearts. Ultrasound and histologic analysis of transmural myocardial wedge samples confirmed that the apparent backscatter could be reproducibly mapped to fiber orientation (angle of the fiber relative to the direction of insonification). These data provided a quantitative relationship between the apparent backscatter and fiber angle that was applied to whole-heart images. Myocardial fiber architecture was successfully measured in rat hearts. Quantifying myocardial fiber architecture, using apparent backscatter, provides a number of advantages, including its scalable use from rodents to man, its rapid low-cost acquisition and minimal contraindications. The method outlined in this study provides a method for investigators to begin detailed assessments of how the myocardial fiber architecture changes in preclinical disease models, which can be immediately translated into the clinic.
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Affiliation(s)
- Michelle L Milne
- Department of Physics, St. Mary's College of Maryland, St. Mary's City, MD, USA
| | - Brianna M Schick
- Department of Physiology, Wayne State University, Detroit, MI, USA
| | - Thamer Alkhazal
- Department of Physiology, Wayne State University, Detroit, MI, USA
| | - Charles S Chung
- Department of Physiology, Wayne State University, Detroit, MI, USA.
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Guerrero QW, Feltovich H, Rosado-Mendez IM, Carlson LC, Hallcor TJ. Quantitative Ultrasound Biomarkers Based on Backscattered Acoustic Power: Potential for Quantifying Remodeling of the Human Cervix during Pregnancy. ULTRASOUND IN MEDICINE & BIOLOGY 2019; 45:429-439. [PMID: 30473174 PMCID: PMC6324963 DOI: 10.1016/j.ultrasmedbio.2018.08.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 08/24/2018] [Accepted: 08/27/2018] [Indexed: 05/21/2023]
Abstract
As pregnancy progresses, the cervix remodels from a rigid structure to one pliable enough to allow delivery of a fetus, a process that involves progressive disorganization of cervical microstructure. Quantitative ultrasound biomarkers that may detect this process include those derived from the backscattered echo signal, namely, acoustic attenuation and backscattered power loss. We recently reported that attenuation and backscattered power loss are affected by tissue anisotropy and heterogeneity in the ex vivo cervix. In this study, we compared attenuation and backscattered power difference in a group of women in early pregnancy (first trimester) with those in a group in late pregnancy (third trimester). We observed a significant decrease in the backscattered power difference in late as compared with early pregnancy, suggesting decreased microstructural organization in late pregnancy, a finding that is consistent with animal models of cervical remodeling. In contrast, we found no difference in attenuation between the time points. These results suggest that the backscattered power difference, but perhaps not attenuation, may be a useful clinical biomarker of cervical remodeling.
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Affiliation(s)
- Quinton W Guerrero
- Medical Physics Department, University of Wisconsin, Madison, Wisconsin, USA
| | - Helen Feltovich
- Medical Physics Department, University of Wisconsin, Madison, Wisconsin, USA; Maternal Fetal Medicine Department, Intermountain Healthcare, Provo, Utah, USA
| | | | - Lindsey C Carlson
- Medical Physics Department, University of Wisconsin, Madison, Wisconsin, USA; Maternal Fetal Medicine Department, Intermountain Healthcare, Provo, Utah, USA
| | - Timothy J Hallcor
- Medical Physics Department, University of Wisconsin, Madison, Wisconsin, USA.
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Abstract
There has been an increasing interest in studying cardiac fibers in order to improve the current knowledge regarding the mechanical and physiological properties of the heart during heart failure (HF), particularly early HF. Having a thorough understanding of the changes in cardiac fiber orientation may provide new insight into the mechanisms behind the progression of left ventricular (LV) remodeling and HF. We conducted a systematic review on various technologies for imaging cardiac fibers and its link to HF. This review covers literature reports from 1900 to 2017. PubMed and Google Scholar databases were searched using the keywords "cardiac fiber" and "heart failure" or "myofiber" and "heart failure." This review highlights imaging methodologies, including magnetic resonance diffusion tensor imaging (MR-DTI), ultrasound, and other imaging technologies as well as their potential applications in basic and translational research on the development and progression of HF. MR-DTI and ultrasound have been most useful and significant in evaluating cardiac fibers and HF. New imaging technologies that have the ability to measure cardiac fiber orientations and identify structural and functional information of the heart will advance basic research and clinical diagnoses of HF.
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Affiliation(s)
- Shana R Watson
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - James D Dormer
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Baowei Fei
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA. .,Winship Cancer Institute of Emory University, Atlanta, GA, USA. .,Department of Mathematics and Computer Science, Emory University, Atlanta, GA, USA. .,Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA. .,Quantitative Bioimaging Laboratory, Department of Radiology and Imaging Sciences, School of Medicine, Emory University, Atlanta, United States.
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Guerrero QW, Feltovich H, Rosado-Mendez IM, Carlson LC, Li G, Hall TJ. Anisotropy and Spatial Heterogeneity in Quantitative Ultrasound Parameters: Relevance to the Study of the Human Cervix. ULTRASOUND IN MEDICINE & BIOLOGY 2018; 44:1493-1503. [PMID: 29661482 PMCID: PMC5960605 DOI: 10.1016/j.ultrasmedbio.2018.02.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/20/2018] [Accepted: 02/22/2018] [Indexed: 05/13/2023]
Abstract
Imaging biomarkers based on quantitative ultrasound can offer valuable information about properties that inform tissue function and behavior such as microstructural organization (e.g., collagen alignment) and viscoelasticity (i.e., compliance). For example, the cervix feels softer as its microstructure remodels during pregnancy, an increase in compliance that can be objectively quantified with shear wave speed and therefore shear wave speed estimation is a potential biomarker of cervical remodeling. Other proposed biomarkers include parameters derived from the backscattered echo signal, such as attenuation and backscattered power loss, because such parameters can provide insight into tissue microstructural alignment and organization. Of these, attenuation values for the pregnant cervix have been reported, but large estimate variance reduces their clinical value. That said, parameter estimates based on the backscattered echo signal may be incorrect if assumptions they rely on, such as tissue isotropy and homogeneity, are violated. For that reason, we explored backscatter and attenuation parameters as potential biomarkers of cervical remodeling via careful investigation of the assumptions of isotropy and homogeneity in cervical tissue. Specifically, we estimated the angle- and spatial-dependence of parameters of backscattered power and acoustic attenuation in the ex vivo human cervix, using the reference phantom method and electronic steering of the ultrasound beam. We found that estimates are anisotropic and spatially heterogeneous, presumably because the tissue itself is anisotropic and heterogeneous. We conclude that appropriate interpretation of imaging biomarkers of cervical remodeling must account for tissue anisotropy and heterogeneity.
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Affiliation(s)
| | - Helen Feltovich
- Medical Physics Department, University of Wisconsin, Madison, WI, USA; Maternal Fetal Medicine, Obstetrics & Gynecology, Intermountain Healthcare, Provo, UT, USA
| | | | - Lindsey C Carlson
- Medical Physics Department, University of Wisconsin, Madison, WI, USA; Maternal Fetal Medicine, Obstetrics & Gynecology, Intermountain Healthcare, Provo, UT, USA
| | - Geng Li
- Biostatistics and Medical Informatics Department, University of Wisconsin, Madison, WI, USA
| | - Timothy J Hall
- Medical Physics Department, University of Wisconsin, Madison, WI, USA.
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Qin X, Wang S, Shen M, Lu G, Zhang X, Wagner MB, Fei B. Simulating cardiac ultrasound image based on MR diffusion tensor imaging. Med Phys 2016; 42:5144-56. [PMID: 26328966 DOI: 10.1118/1.4927788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Cardiac ultrasound simulation can have important applications in the design of ultrasound systems, understanding the interaction effect between ultrasound and tissue and setting the ground truth for validating quantification methods. Current ultrasound simulation methods fail to simulate the myocardial intensity anisotropies. New simulation methods are needed in order to simulate realistic ultrasound images of the heart. METHODS The proposed cardiac ultrasound image simulation method is based on diffusion tensor imaging (DTI) data of the heart. The method utilizes both the cardiac geometry and the fiber orientation information to simulate the anisotropic intensities in B-mode ultrasound images. Before the simulation procedure, the geometry and fiber orientations of the heart are obtained from high-resolution structural MRI and DTI data, respectively. The simulation includes two important steps. First, the backscatter coefficients of the point scatterers inside the myocardium are processed according to the fiber orientations using an anisotropic model. Second, the cardiac ultrasound images are simulated with anisotropic myocardial intensities. The proposed method was also compared with two other nonanisotropic intensity methods using 50 B-mode ultrasound image volumes of five different rat hearts. The simulated images were also compared with the ultrasound images of a diseased rat heart in vivo. A new segmental evaluation method is proposed to validate the simulation results. The average relative errors (AREs) of five parameters, i.e., mean intensity, Rayleigh distribution parameter σ, and first, second, and third quartiles, were utilized as the evaluation metrics. The simulated images were quantitatively compared with real ultrasound images in both ex vivo and in vivo experiments. RESULTS The proposed ultrasound image simulation method can realistically simulate cardiac ultrasound images of the heart using high-resolution MR-DTI data. The AREs of their proposed method are 19% for the mean intensity, 17.7% for the scale parameter of Rayleigh distribution, 36.8% for the first quartile of the image intensities, 25.2% for the second quartile, and 19.9% for the third quartile. In contrast, the errors of the other two methods are generally five times more than those of their proposed method. CONCLUSIONS The proposed simulation method uses MR-DTI data and realistically generates cardiac ultrasound images with anisotropic intensities inside the myocardium. The ultrasound simulation method could provide a tool for many potential research and clinical applications in cardiac ultrasound imaging.
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Affiliation(s)
- Xulei Qin
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30329
| | - Silun Wang
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329
| | - Ming Shen
- Emory University Department of Pediatrics and Children's Healthcare of Atlanta, Atlanta, Georgia 30322
| | - Guolan Lu
- Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia 30329
| | - Xiaodong Zhang
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329
| | - Mary B Wagner
- Emory University Department of Pediatrics and Children's Healthcare of Atlanta, Atlanta, Georgia 30322
| | - Baowei Fei
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30329; Department of Mathematics and Computer Science, Emory University, Atlanta, Georgia 30329; and Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia 30329
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Milne ML, Singh GK, Miller JG, Wallace KD, Holland MR. Toward 3-D Echocardiographic Determination of Regional Myofiber Structure. ULTRASOUND IN MEDICINE & BIOLOGY 2016; 42:607-18. [PMID: 26589530 PMCID: PMC4711925 DOI: 10.1016/j.ultrasmedbio.2015.09.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 09/15/2015] [Accepted: 09/27/2015] [Indexed: 05/10/2023]
Abstract
As a step toward the goal of relating changes in underlying myocardial structure to observed altered cardiac function in the hearts of individual patients, this study addresses the feasibility of creating echocardiography-derived maps of regional myocardial fiber structure for entire, intact, excised sheep hearts. Backscatter data were obtained from apical echocardiographic images acquired with a clinical ultrasonic imaging system and used to determine local fiber orientations in each of seven hearts. Systematic acquisition across the entire heart volume provided information sufficient to give a complete map for each heart. Results from the echocardiography-derived fiber maps compare favorably with corresponding results derived from diffusion tensor magnetic resonance imaging. The results of this study provide evidence of the feasibility of using echocardiographic methods to generate individualized whole heart fiber maps for patients.
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Affiliation(s)
- Michelle L Milne
- Department of Physics, St. Mary's College of Maryland, St. Mary's City, Maryland, USA.
| | - Gautam K Singh
- Department of Pediatrics, Washington University in St. Louis, Saint Louis, Missouri, USA
| | - James G Miller
- Department of Physics, Washington University in St. Louis, Saint Louis, Missouri, USA
| | | | - Mark R Holland
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, IUPUI, Indianapolis, Indiana, USA
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