1
|
Wilson AJ, Sands GB, LeGrice IJ, Young AA, Ennis DB. Myocardial Mesostructure and Mesofunction. Am J Physiol Heart Circ Physiol 2022; 323:H257-H275. [PMID: 35657613 PMCID: PMC9273275 DOI: 10.1152/ajpheart.00059.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The complex and highly organized structural arrangement of some five billion cardiomyocytes directs the coordinated electrical activity and mechanical contraction of the human heart. The characteristic transmural change in cardiomyocyte orientation underlies base-to-apex shortening, circumferential shortening, and left ventricular torsion during contraction. Individual cardiomyocytes shorten approximately 15% and increase in diameter approximately 8%. Remarkably, however, the left ventricular wall thickens by up to 30-40%. To accommodate this, the myocardium must undergo significant structural rearrangement during contraction. At the mesoscale, collections of cardiomyocytes are organized into sheetlets, and sheetlet shear is the fundamental mechanism of rearrangement that produces wall thickening. Herein we review the histological and physiological studies of myocardial mesostructure that have established the sheetlet shear model of wall thickening. Recent developments in tissue clearing techniques allow for imaging of whole hearts at the cellular scale, while magnetic resonance imaging (MRI) and computed tomography (CT) can image the myocardium at the mesoscale (tens to hundreds of microns) to resolve cardiomyocyte orientation and organization. Through histology, cardiac diffusion tensor imaging (cDTI) and other modalities, mesostructural sheetlets have been confirmed in both animal and human hearts. Recent in vivo cDTI methods have measured reorientation of sheetlets during the cardiac cycle. We also examine the role of pathological cardiac remodeling on sheetlet organization and reorientation, and the impact this has on ventricular function and dysfunction. We also review the unresolved mesostructural questions and challenges that may direct future work in the field.
Collapse
Affiliation(s)
- Alexander J Wilson
- Department of Radiology, Stanford University, Stanford, CA, United States.,Stanford Cardiovascular Institute, Stanford University, Stanford, CA, United States
| | - Gregory B Sands
- Auckland Bioengineering Institute, University of Auckland, New Zealand
| | - Ian J LeGrice
- Auckland Bioengineering Institute, University of Auckland, New Zealand.,Department of Physiology, University of Auckland, New Zealand
| | - Alistair A Young
- Department of Anatomy and Medical Imaging, University of Auckland, New Zealand.,Department of Biomedical Engineering, King's College London, United Kingdom
| | - Daniel B Ennis
- Department of Radiology, Stanford University, Stanford, CA, United States.,Veterans Administration Palo Alto Health Care System, Palo Alto, CA, United States
| |
Collapse
|
2
|
Tang P, Kirby MA, Le N, Li Y, Zeinstra N, Lu GN, Murry CE, Zheng Y, Wang RK. Polarization sensitive optical coherence tomography with single input for imaging depth-resolved collagen organizations. LIGHT, SCIENCE & APPLICATIONS 2021; 10:237. [PMID: 34819490 PMCID: PMC8613400 DOI: 10.1038/s41377-021-00679-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 10/26/2021] [Accepted: 11/10/2021] [Indexed: 05/02/2023]
Abstract
Collagen organization plays an important role in maintaining structural integrity and determining tissue function. Polarization-sensitive optical coherence tomography (PSOCT) is a promising noninvasive three-dimensional imaging tool for mapping collagen organization in vivo. While PSOCT systems with multiple polarization inputs have demonstrated the ability to visualize depth-resolved collagen organization, systems, which use a single input polarization state have not yet demonstrated sufficient reconstruction quality. Herein we describe a PSOCT based polarization state transmission model that reveals the depth-dependent polarization state evolution of light backscattered within a birefringent sample. Based on this model, we propose a polarization state tracing method that relies on a discrete differential geometric analysis of the evolution of the polarization state in depth along the Poincare sphere for depth-resolved birefringent imaging using only one single input polarization state. We demonstrate the ability of this method to visualize depth-resolved myocardial architecture in both healthy and infarcted rodent hearts (ex vivo) and collagen structures responsible for skin tension lines at various anatomical locations on the face of a healthy human volunteer (in vivo).
Collapse
Affiliation(s)
- Peijun Tang
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
| | - Mitchell A Kirby
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
| | - Nhan Le
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
| | - Yuandong Li
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
| | - Nicole Zeinstra
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
| | - G Nina Lu
- Department of Otolaryngology- Head and Neck Surgery, Facial Plastic and Reconstructive Surgery, University of Washington, Seattle, WA, 98195, USA
| | - Charles E Murry
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98109, USA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA, 98109, USA
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98109, USA
| | - Ying Zheng
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98109, USA
| | - Ruikang K Wang
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA.
- Department of Ophthalmology, University of Washington, Seattle, WA, 98105, USA.
| |
Collapse
|
3
|
Dejea H, Bonnin A, Cook AC, Garcia-Canadilla P. Cardiac multi-scale investigation of the right and left ventricle ex vivo: a review. Cardiovasc Diagn Ther 2020; 10:1701-1717. [PMID: 33224784 DOI: 10.21037/cdt-20-269] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The heart is a complex multi-scale system composed of components integrated at the subcellular, cellular, tissue and organ levels. The myocytes, the contractile elements of the heart, form a complex three-dimensional (3D) network which enables propagation of the electrical signal that triggers the contraction to efficiently pump blood towards the whole body. Cardiovascular diseases (CVDs), a major cause of mortality in developed countries, often lead to cardiovascular remodeling affecting cardiac structure and function at all scales, from myocytes and their surrounding collagen matrix to the 3D organization of the whole heart. As yet, there is no consensus as to how the myocytes are arranged and packed within their connective tissue matrix, nor how best to image them at multiple scales. Cardiovascular imaging is routinely used to investigate cardiac structure and function as well as for the evaluation of cardiac remodeling in CVDs. For a complete understanding of the relationship between structural remodeling and cardiac dysfunction in CVDs, multi-scale imaging approaches are necessary to achieve a detailed description of ventricular architecture along with cardiac function. In this context, ventricular architecture has been extensively studied using a wide variety of imaging techniques: ultrasound (US), optical coherence tomography (OCT), microscopy (confocal, episcopic, light sheet, polarized light), magnetic resonance imaging (MRI), micro-computed tomography (micro-CT) and, more recently, synchrotron X-ray phase contrast imaging (SR X-PCI). Each of these techniques have their own set of strengths and weaknesses, relating to sample size, preparation, resolution, 2D/3D capabilities, use of contrast agents and possibility of performing together with in vivo studies. Therefore, the combination of different imaging techniques to investigate the same sample, thus taking advantage of the strengths of each method, could help us to extract the maximum information about ventricular architecture and function. In this review, we provide an overview of available and emerging cardiovascular imaging techniques for assessing myocardial architecture ex vivo and discuss their utility in being able to quantify cardiac remodeling, in CVDs, from myocyte to whole organ.
Collapse
Affiliation(s)
- Hector Dejea
- Paul Scherrer Institut, Villigen PSI, Villigen, Switzerland.,Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Anne Bonnin
- Paul Scherrer Institut, Villigen PSI, Villigen, Switzerland
| | - Andrew C Cook
- Institute of Cardiovascular Science, University College London, London, UK
| | - Patricia Garcia-Canadilla
- Institute of Cardiovascular Science, University College London, London, UK.,Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| |
Collapse
|
4
|
Zhou X, Dormer J, Fei B. Development of a polarized hyperspectral microscope for cardiac fiber orientation imaging. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2020; 11215:112150V. [PMID: 32528213 PMCID: PMC7288758 DOI: 10.1117/12.2549720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Myocardial fiber orientation is closely related to the functions of the heart. The development of imaging tools for depicting myocardial fiber orientation is important. We developed a polarized hyperspectral imaging microscope (PHSIM) for cardiac fiber orientation imaging, which is capable of polarimetric imaging and hyperspectral imaging. Polarimetric imaging is realized by the integration of two polarizers. Hyperspectral imaging is realized by snapscan Preliminary imaging experiments were implemented on an unstained paraffin embedded tissue slides of a chicken heart. We also set up a Monte Carlo simulation program based on the cylinder optical model to simulate the cardiac fiber structure of the sample and the optical setup of the PHSIM system, in which we can calculate the system output light intensity related to cardiac fiber orientation. According to the imaging and simulation results, there exists a variation of intensity of acquired images with the polar angles from the maximum to the minimum under different wavelengths, which should relate to the orientation of cardiac fibers. In addition, there is a shift of the polar angle where the maximum intensity appears when a rotation of the sample happened both in the simulation and imaging experiments. Further work is required for imaging more types of myocardial tissues at different parts and the design of a complete quantitative model to describe the relations among polar angles, wavelengths, and cardiac fiber orientations.
Collapse
Affiliation(s)
- Ximing Zhou
- The University of Texas at Dallas, Department of Bioengineering, Richardson, TX
| | - James Dormer
- The University of Texas at Dallas, Department of Bioengineering, Richardson, TX
| | - Baowei Fei
- The University of Texas at Dallas, Department of Bioengineering, Richardson, TX
- University of Texas Southwestern Medical Center, Department of Radiology, Dallas, TX
| |
Collapse
|
5
|
Yao G, Duan D. High-resolution 3D tractography of fibrous tissue based on polarization-sensitive optical coherence tomography. Exp Biol Med (Maywood) 2020; 245:273-281. [PMID: 31813275 PMCID: PMC7370596 DOI: 10.1177/1535370219894332] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Fibrous tissues play important roles in many parts of the body. Their highly organized directional structure is essential in achieving their normal biomechanical and physiological functions. Disruption of the typical fiber organization in these tissues is often linked to pathological changes and disease progression. Tractography is a specialized imaging method that can reveal the detailed fiber architecture. Here, we review recent developments in high-resolution optical tractography using Jones matrix polarization-sensitive optical coherence tomography. We also illustrate the use of this new tractography technology for visualizing depth-resolved, three-dimensional fibrous structures and quantifying tissue damages in several major fibrous tissues.
Collapse
Affiliation(s)
- Gang Yao
- Department of Biomedical, Biological & Chemical Engineering, University of Missouri, Columbia, MO 65211, USA
| | - Dongsheng Duan
- Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, MO 65211, USA
| |
Collapse
|
6
|
Lye TH, Marboe CC, Hendon CP. Imaging of subendocardial adipose tissue and fiber orientation distributions in the human left atrium using optical coherence tomography. J Cardiovasc Electrophysiol 2019; 30:2950-2959. [PMID: 31661178 PMCID: PMC6916589 DOI: 10.1111/jce.14255] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 10/23/2019] [Accepted: 10/25/2019] [Indexed: 12/18/2022]
Abstract
Background Optical coherence tomography (OCT) has the potential to provide real‐time imaging guidance for atrial fibrillation ablation, with promising results for lesion monitoring. OCT can also offer high‐resolution imaging of tissue composition, but there is insufficient cardiac OCT data to inform the use of OCT to reveal important tissue architecture of the human left atrium. Thus, the objective of this study was to define OCT imaging data throughout the human left atrium, focusing on the distribution of adipose tissue and fiber orientation as seen from the endocardium. Methods and Results Human hearts (n = 7) were acquired for imaging the left atrium with OCT. A spectral‐domain OCT system with 1325 nm center wavelength, 6.5 μm axial resolution, 15 μm lateral resolution, and a maximum imaging depth of 2.51 mm in the air was used. Large‐scale OCT image maps of human left atrial tissue were developed, with adipose thickness and fiber orientation extracted from the imaging data. OCT imaging showed scattered distributions of adipose tissue around the septal and pulmonary vein regions, up to a depth of about 0.43 mm from the endocardial surface. The total volume of adipose tissue detected by OCT over one left atrium ranged from 1.42 to 28.74 mm3. Limited fiber orientation information primarily around the pulmonary veins and the septum could be identified. Conclusion OCT imaging could provide adjunctive information on the distribution of subendocardial adipose tissue, particularly around thin areas around the pulmonary veins and septal regions. Variations in OCT‐detected tissue composition could potentially assist ablation guidance.
Collapse
Affiliation(s)
- Theresa H Lye
- Department of Electrical Engineering, Columbia University, New York, NY
| | - Charles C Marboe
- Department of Pathology, Columbia University Medical Center, New York, NY
| | | |
Collapse
|
7
|
Huynh RN, Pesante B, Nehmetallah G, Raub CB. Polarized reflectance from articular cartilage depends upon superficial zone collagen network microstructure. BIOMEDICAL OPTICS EXPRESS 2019; 10:5518-5534. [PMID: 31799028 PMCID: PMC6865123 DOI: 10.1364/boe.10.005518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 05/02/2023]
Abstract
Polarized reflectance from articular cartilage involves light scattering dependent on surface features, sub-surface optical properties, and collagen birefringence. To understand how surface roughness, zonal collagen microstructure, and chondrocyte organization contribute to polarized reflectance signals, experiments were conducted on bovine cartilage explants and osteochondral cores to compare polarized reflectance texture with split lines and relate these signals to cartilage zonal features and chondrocyte distribution. Texture parameter sensitivity to articular surface damage was determined from polarized reflectance maps and optimized to detect surface damage. Results indicate that polarized reflectance texture predominantly derives from the superficial zone collagen network, while the parameter average value also depends on surface roughness and total cartilage thickness.
Collapse
Affiliation(s)
- R. N. Huynh
- Department of Biomedical Engineering, The Catholic University of America, 620 Michigan Ave NE., Washington, DC 20064, USA
| | - B. Pesante
- Department of Biomedical Engineering, The Catholic University of America, 620 Michigan Ave NE., Washington, DC 20064, USA
| | - G. Nehmetallah
- Department of Electrical Engineering and Computer Science, The Catholic University of America, 620 Michigan Ave NE., Washington, DC 20064, USA
| | - C. B. Raub
- Department of Biomedical Engineering, The Catholic University of America, 620 Michigan Ave NE., Washington, DC 20064, USA
| |
Collapse
|
8
|
Ravanfar M, Yao G. Simultaneous tractography and elastography imaging of the zone-specific structural and mechanical responses in articular cartilage under compressive loading. BIOMEDICAL OPTICS EXPRESS 2019; 10:3241-3256. [PMID: 31467777 PMCID: PMC6706024 DOI: 10.1364/boe.10.003241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 05/28/2019] [Accepted: 05/29/2019] [Indexed: 05/09/2023]
Abstract
We quantified the precise zonal cartilage structural and mechanical responses to unconfined compressive loading by using simultaneous PSOCT based optical tractography and elastography imaging. Twelve bovine knee articular cartilage samples from six animals were imaged under bulk compression from 4% to 20%. The results revealed strong evidence that the conventional radial zone could be divided into two sub-zones with distinct mechanical properties. The "upper" part of the radial zone played a critical role in "absorbing" the mechanical compression. The study also showed that the zonal fiber organization greatly affected the cartilage structural and mechanical responses. A strong correlation was observed between the optical birefringence and logarithm of the Young's modulus. These new results provide useful information for improving mechanical modeling of articular cartilage and developing better cartilage-mimetic biomaterials.
Collapse
|
9
|
Hendon CP, Lye TH, Yao X, Gan Y, Marboe CC. Optical coherence tomography imaging of cardiac substrates. Quant Imaging Med Surg 2019; 9:882-904. [PMID: 31281782 DOI: 10.21037/qims.2019.05.09] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cardiovascular disease is the leading cause of morbidity and mortality in the United States. Knowledge of a patient's heart structure will help to plan procedures, potentially identifying arrhythmia substrates, critical structures to avoid, detect transplant rejection, and reduce ambiguity when interpreting electrograms and functional measurements. Similarly, basic research of numerous cardiac diseases would greatly benefit from structural imaging at cellular scale. For both applications imaging on the scale of a myocyte is needed, which is approximately 100 µm × 10 µm. The use of optical coherence tomography (OCT) as a tool for characterizing cardiac tissue structure and function has been growing in the past two decades. We briefly review OCT principles and highlight important considerations when imaging cardiac muscle. In particular, image penetration, tissue birefringence, and light absorption by blood during in vivo imaging are important factors when imaging the heart with OCT. Within the article, we highlight applications of cardiac OCT imaging including imaging heart tissue structure in small animal models, quantification of myofiber organization, monitoring of radiofrequency ablation (RFA) lesion formation, structure-function analysis enabled by functional extensions of OCT and multimodal analysis and characterizing important substrates within the human heart. The review concludes with a summary and future outlook of OCT imaging the heart, which is promising with progress in optical catheter development, functional extensions of OCT, and real time image processing to enable dynamic imaging and real time tracking during therapeutic procedures.
Collapse
Affiliation(s)
| | | | | | - Yu Gan
- Columbia University, New York, NY, USA
| | | |
Collapse
|
10
|
Tissue-Specific Optical Mapping Models of Swine Atria Informed by Optical Coherence Tomography. Biophys J 2019; 114:1477-1489. [PMID: 29590604 PMCID: PMC5883619 DOI: 10.1016/j.bpj.2018.01.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 01/12/2018] [Accepted: 01/30/2018] [Indexed: 11/21/2022] Open
Abstract
Computational models and experimental optical mapping of cardiac electrophysiology serve as powerful tools to investigate the underlying mechanisms of arrhythmias. Modeling can also aid the interpretation of optical mapping signals, which may have different characteristics with respect to the underlying electrophysiological signals they represent. However, despite the prevalence of atrial arrhythmias such as atrial fibrillation, models of optical electrical mapping incorporating realistic structure of the atria are lacking. Therefore, we developed image-based models of atrial tissue using structural information extracted from optical coherence tomography (OCT), which can provide volumetric tissue characteristics in high resolution. OCT volumetric data of four swine atrial tissue samples were used to develop models incorporating tissue geometry, tissue-specific myofiber orientation, and ablation lesion regions. We demonstrated the use of these models through electrophysiology and photon scattering simulations. Changes in transmural electrical conduction were observed with the inclusion of OCT-derived, depth-resolved fiber orientation. Additionally, the amplitude of optical mapping signals were not found to correspond with lesion transmurality because of lesion geometry and electrical propagation occurring beyond excitation light penetration. This work established a framework for the development of tissue-specific models of atrial tissue derived from OCT imaging data, which can be useful in future investigations of electrophysiology and optical mapping signals with respect to realistic atrial tissue structure.
Collapse
|
11
|
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.
Collapse
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.
| |
Collapse
|
12
|
Li ZF, Qiu SP, Wu SL, Li H. Quantification of collagen fiber orientation based on center line of second harmonic generation image for naturally aging skins. ACTA ACUST UNITED AC 2018. [DOI: 10.1007/s11801-018-8023-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
13
|
Li Z, Tang Q, Dickfeld T, Chen Y. Depth-resolved mapping of muscular bundles in myocardium pulmonary junction using optical coherence tomography. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-5. [PMID: 29981228 PMCID: PMC8357322 DOI: 10.1117/1.jbo.23.7.076004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 06/21/2018] [Indexed: 05/31/2023]
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia and has high patient morbidity. One of the root causes of AF is initiating triggers from atrial myocardium extending into the pulmonary veins. Visualizing the muscular bundles of myocardial extension is essential to guide the catheter radio-frequency ablation and confirm the curative tissue necrosis thereafter. We applied optical coherence tomography (OCT) for direct visualization of cardial muscle extension in myocardium pulmonary junction. Two perspectives (cross-sectional and en face images) are presented for imaging myocardial extensions. The results demonstrated that cross-sectional images can quickly locate the myocardium pulmonary junction. And en face images provide depth-resolved arrangement information of muscular bundles in the myocardium pulmonary junction. The results indicated that OCT could potentially be used to guide catheter radio-frequency ablation for treatment of AF.
Collapse
Affiliation(s)
- Zhifang Li
- Ministry of Education, Fujian Normal University, College of Photonic and Electronic Engineering, Fujian Provincial Engineering Technology Research Center of Photoelectric Sensing Application, Key Laboratory of Optoelectronic Science and Technology for Medicine, Fujian Provincial Key Laboratory of Photonics Technology, Fuzhou, China
| | - Qinggong Tang
- University of Maryland, Fischell Department of Bioengineering, College Park, Maryland, United States
| | - Timm Dickfeld
- University of Maryland, School of Medicine, Baltimore, Maryland, United States
| | - Yu Chen
- Ministry of Education, Fujian Normal University, College of Photonic and Electronic Engineering, Fujian Provincial Engineering Technology Research Center of Photoelectric Sensing Application, Key Laboratory of Optoelectronic Science and Technology for Medicine, Fujian Provincial Key Laboratory of Photonics Technology, Fuzhou, China
- University of Maryland, Fischell Department of Bioengineering, College Park, Maryland, United States
| |
Collapse
|
14
|
Wang Y, Ravanfar M, Zhang K, Duan D, Yao G. Automatic quantification of microscopic heart damage in a mouse model of Duchenne muscular dystrophy using optical polarization tractography. JOURNAL OF BIOPHOTONICS 2018; 11:e201700284. [PMID: 29314725 DOI: 10.1002/jbio.201700284] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 12/06/2017] [Accepted: 01/03/2018] [Indexed: 06/07/2023]
Abstract
Quantification of microscopic myocardium damage in a diseased heart is important in studying disease progression and evaluating treatment outcome. However, it is challenging to use traditional histology and existing medical imaging modalities to quantify all microscopic damages in a small animal heart. Here, a method was developed for fast visualization and quantification of focal tissue damage in the mouse heart based on the fiber alignment index of the local myofiber organization obtained in optical polarization tractography (OPT). This method was tested in freshly excised hearts of the mdx4cv mouse, a commonly used mouse model for studying Duchenne cardiomyopathy. The hearts of age-matched C57BL/6 mice were also imaged as the normal controls. The results revealed a significant amount of damage in the mdx4cv hearts. Histology comparisons confirmed the damage identified by OPT. This fast and automatic method may greatly enhance preclinical studies in murine models of heart diseases.
Collapse
Affiliation(s)
- Yuanbo Wang
- Department of Bioengineering, University of Missouri, Columbia, Missouri
| | | | - Keqing Zhang
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, Missouri
| | - Dongsheng Duan
- Department of Bioengineering, University of Missouri, Columbia, Missouri
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, Missouri
| | - Gang Yao
- Department of Bioengineering, University of Missouri, Columbia, Missouri
| |
Collapse
|
15
|
Castonguay A, Lefebvre J, Lesage F, Pouliot P. Comparing three-dimensional serial optical coherence tomography histology to MRI imaging in the entire mouse brain. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-9. [PMID: 29313322 DOI: 10.1117/1.jbo.23.1.016008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 12/12/2017] [Indexed: 06/07/2023]
Abstract
An automated serial histology setup combining optical coherence tomography (OCT) imaging with vibratome sectioning was used to image eight wild type mouse brains. The datasets resulted in thousands of volumetric tiles resolved at a voxel size of (4.9×4.9×6.5) μm3 stitched back together to give a three-dimensional map of the brain from which a template OCT brain was obtained. To assess deformation caused by tissue sectioning, reconstruction algorithms, and fixation, OCT datasets were compared to both in vivo and ex vivo magnetic resonance imaging (MRI) imaging. The OCT brain template yielded a highly detailed map of the brain structure, with a high contrast in white matter fiber bundles and was highly resemblant to the in vivo MRI template. Brain labeling using the Allen brain framework showed little variation in regional brain volume among imaging modalities with no statistical differences. The high correspondence between the OCT template brain and its in vivo counterpart demonstrates the potential of whole brain histology to validate in vivo imaging.
Collapse
Affiliation(s)
| | - Joël Lefebvre
- École Polytechnique de Montréal, Montréal, Québec, Canada
| | - Frédéric Lesage
- École Polytechnique de Montréal, Montréal, Québec, Canada
- Institut de Cardiologie de Montréal, Montréal, Québec, Canada
| | - Philippe Pouliot
- École Polytechnique de Montréal, Montréal, Québec, Canada
- Institut de Cardiologie de Montréal, Montréal, Québec, Canada
| |
Collapse
|
16
|
Castonguay A, Lefebvre J, Pouliot P, Avti P, Moeini M, Lesage F. Serial optical coherence scanning reveals an association between cardiac function and the heart architecture in the aging rodent heart. BIOMEDICAL OPTICS EXPRESS 2017; 8:5027-5038. [PMID: 29188099 PMCID: PMC5695949 DOI: 10.1364/boe.8.005027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/11/2017] [Accepted: 10/12/2017] [Indexed: 05/10/2023]
Abstract
Normal aging is accompanied by structural changes in the heart architecture. To explore this remodeling, we used a serial optical coherence tomography scanner to image entire mouse hearts at micron scale resolution. Ex vivo hearts of 7 young (4 months) and 5 old (24 months) C57BL/6 mice were acquired with the imaging platform. OCT of the myocardium revealed myofiber orientation changing linearly from the endocardium to the epicardium. In old mice, this rate of change was lower when compared to young mice while the average volume of old mice hearts was significantly larger (p<0.05). Myocardial wall thickening was also accompanied by extracellular spacing in the endocardium, resulting in a lower OCT attenuation coefficient in old mice endocardium (p<0.05). Prior to serial sectioning, cardiac function of the same hearts was imaged in vivo using MRI and revealed a reduced ejection fraction with aging. The use of a serial optical coherence tomography scanner allows new insight into fine age-related changes of the heart associated with changes in heart function.
Collapse
Affiliation(s)
- Alexandre Castonguay
- École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal QC, H3C3A7, Canada
| | - Joël Lefebvre
- École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal QC, H3C3A7, Canada
| | - Philippe Pouliot
- École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal QC, H3C3A7, Canada
- Institut de Cardiologie de Montréal, 5000 rue Bélanger Est, Montréal, QC, H1T1C8, Canada
| | - Pramod Avti
- Department of Biophysics, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India
| | - Mohammad Moeini
- École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal QC, H3C3A7, Canada
- Institut de Cardiologie de Montréal, 5000 rue Bélanger Est, Montréal, QC, H1T1C8, Canada
| | - Frédéric Lesage
- École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal QC, H3C3A7, Canada
- Institut de Cardiologie de Montréal, 5000 rue Bélanger Est, Montréal, QC, H1T1C8, Canada
| |
Collapse
|
17
|
Wang Y, Zhang K, Duan D, Yao G. Heart structural remodeling in a mouse model of Duchenne cardiomyopathy revealed using optical polarization tractography [Invited]. BIOMEDICAL OPTICS EXPRESS 2017; 8:1271-1276. [PMID: 28663827 PMCID: PMC5480542 DOI: 10.1364/boe.8.001271] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/27/2017] [Accepted: 01/28/2017] [Indexed: 05/10/2023]
Abstract
We investigated the heart structural remodeling in the mdx4cv mouse model of Duchenne cardiomyopathy using optical polarization tractography. Whole heart tractography was obtained in freshly dissected hearts from six mdx4cv mice. Six hearts from C57BL/6J mice were also imaged as the normal control. The mdx4cv hearts were significantly larger than the control hearts and had significantly higher between-subject variations in myofiber organization. While both strains showed classic cross-helical fiber organization in the left ventricle, the rate of the myocardial fiber orientation change across the heart wall was significantly altered in the right ventricle of the mdx4cv heart.
Collapse
Affiliation(s)
- Y. Wang
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| | - K. Zhang
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, MO 65211, USA
| | - D. Duan
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, MO 65211, USA
| | - G. Yao
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| |
Collapse
|
18
|
Azinfar L, Ravanfar M, Wang Y, Zhang K, Duan D, Yao G. High resolution imaging of the fibrous microstructure in bovine common carotid artery using optical polarization tractography. JOURNAL OF BIOPHOTONICS 2017; 10:231-241. [PMID: 26663698 DOI: 10.1002/jbio.201500229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 11/04/2015] [Accepted: 11/23/2015] [Indexed: 05/18/2023]
Abstract
The biomechanical properties of artery are primarily determined by the fibrous structures in the vessel wall. Many vascular diseases are associated with alternations in the orientation and alignment of the fibrous structure in the arterial wall. Knowledge on the structural features of the artery wall is crucial to our understanding of the biology of vascular diseases and the development of novel therapies. Optical coherence tomography (OCT) and polarization-sensitive OCT have shown great promise in imaging blood vessels due to their high resolution, fast acquisition, good imaging depth, and large field of view. However, the feasibility of using OCT based methods for imaging fiber orientation and distribution in the arterial wall has not been investigated. Here we show that the optical polarization tractography (OPT), a technology developed from Jones matrix OCT, can reveal the fiber orientation and alignment in the bovine common carotid artery. The fiber orientation and alignment data obtained in OPT provided a robust contrast marker to clearly resolve the intima and media boundary of the carotid artery wall. Optical polarization tractography can visualize fiber orientation and alignment in carotid artery.
Collapse
Affiliation(s)
- Leila Azinfar
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| | | | - Yuanbo Wang
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| | - Keqing Zhang
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, MO 65211, USA
| | - Dongsheng Duan
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, MO 65211, USA
| | - Gang Yao
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| |
Collapse
|
19
|
Yao X, Wang Y, Ravanfar M, Pfeiffer FM, Duan D, Yao G. Nondestructive imaging of fiber structure in articular cartilage using optical polarization tractography. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:116004. [PMID: 27819110 DOI: 10.1117/1.jbo.21.11.116004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/17/2016] [Indexed: 05/18/2023]
Abstract
Collagen fiber orientation plays an important role in determining the structure and function of the articular cartilage. However, there is currently a lack of nondestructive means to image the fiber orientation from the cartilage surface. The purpose of this study is to investigate whether the newly developed optical polarization tractography (OPT) can image fiber structure in articular cartilage. OPT was applied to obtain the depth-dependent fiber orientation in fresh articular cartilage samples obtained from porcine phalanges. For comparison, we also obtained collagen fiber orientation in the superficial zone of the cartilage using the established split-line method. The direction of each split-line was quantified using image processing. The orientation measured in OPT agreed well with those obtained from the split-line method. The correlation analysis of a total of 112 split-lines showed a greater than 0.9 coefficient of determination (R2) between the split-line results and OPT measurements obtained between 40 and 108???m in depth. In addition, the thickness of the superficial layer can also be assessed from the birefringence images obtained in OPT. These results support that OPT provides a nondestructive way to image the collagen fiber structure in articular cartilage. This technology may be valuable for both basic cartilage research and clinical orthopedic applications.
Collapse
Affiliation(s)
- Xuan Yao
- University of Missouri, Department of Bioengineering, 1406 E. Rollins Street, Columbia 65211, United States
| | - Yuanbo Wang
- University of Missouri, Department of Bioengineering, 1406 E. Rollins Street, Columbia 65211, United States
| | - Mohammadreza Ravanfar
- University of Missouri, Department of Bioengineering, 1406 E. Rollins Street, Columbia 65211, United States
| | - Ferris M Pfeiffer
- University of Missouri, Department of Bioengineering, 1406 E. Rollins Street, Columbia 65211, United StatesbUniversity of Missouri, Department of Orthopedic Surgery, 1100 Virginia Avenue, Columbia 65212, United States
| | - Dongsheng Duan
- University of Missouri, Department of Bioengineering, 1406 E. Rollins Street, Columbia 65211, United StatescUniversity of Missouri, Department of Molecular Microbiology and Immunology, One Hospital Drive, Columbia 65212, United States
| | - Gang Yao
- University of Missouri, Department of Bioengineering, 1406 E. Rollins Street, Columbia 65211, United States
| |
Collapse
|
20
|
Wang Y, Ravanfar M, Zhang K, Duan D, Yao G. Mapping 3D fiber orientation in tissue using dual-angle optical polarization tractography. BIOMEDICAL OPTICS EXPRESS 2016; 7:3855-3870. [PMID: 27867698 PMCID: PMC5102555 DOI: 10.1364/boe.7.003855] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/28/2016] [Accepted: 08/29/2016] [Indexed: 05/07/2023]
Abstract
Optical polarization tractography (OPT) has recently been applied to map fiber organization in the heart, skeletal muscle, and arterial vessel wall with high resolution. The fiber orientation measured in OPT represents the 2D projected fiber angle in a plane that is perpendicular to the incident light. We report here a dual-angle extension of the OPT technology to measure the actual 3D fiber orientation in tissue. This method was first verified by imaging the murine extensor digitorum muscle placed at various known orientations in space. The accuracy of the method was further studied by analyzing the 3D fiber orientation of the mouse tibialis anterior muscle. Finally we showed that dual-angle OPT successfully revealed the unique 3D "arcade" fiber structure in the bovine articular cartilage.
Collapse
Affiliation(s)
- Y. Wang
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| | - M. Ravanfar
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| | - K. Zhang
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, MO 65211, USA
| | - D. Duan
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
- Department of Molecular Microbiology & Immunology, University of Missouri, Columbia, MO 65211, USA
| | - G. Yao
- Department of Bioengineering, University of Missouri, Columbia, MO 65211, USA
| |
Collapse
|
21
|
Gan Y, Tsay D, Amir SB, Marboe CC, Hendon CP. Automated classification of optical coherence tomography images of human atrial tissue. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:101407. [PMID: 26926869 PMCID: PMC5995000 DOI: 10.1117/1.jbo.21.10.101407] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 02/05/2016] [Indexed: 05/02/2023]
Abstract
Tissue composition of the atria plays a critical role in the pathology of cardiovascular disease, tissue remodeling, and arrhythmogenic substrates. Optical coherence tomography (OCT) has the ability to capture the tissue composition information of the human atria. In this study, we developed a region-based automated method to classify tissue compositions within human atria samples within OCT images. We segmented regional information without prior information about the tissue architecture and subsequently extracted features within each segmented region. A relevance vector machine model was used to perform automated classification. Segmentation of human atrial ex vivo datasets was correlated with trichrome histology and our classification algorithm had an average accuracy of 80.41% for identifying adipose, myocardium, fibrotic myocardium, and collagen tissue compositions.
Collapse
Affiliation(s)
- Yu Gan
- Columbia University, Department of Electrical Engineering, 500 West 120th Street, New York, New York 10027, United States
| | - David Tsay
- Columbia NY Presbyterian Hospital, 630 West 168th Street, New York, New York 10032, United States
| | - Syed B. Amir
- Columbia University, Department of Electrical Engineering, 500 West 120th Street, New York, New York 10027, United States
| | - Charles C. Marboe
- Columbia University Medical Center, 630 West 168th Street, New York, New York 10032, United States
| | - Christine P. Hendon
- Columbia University, Department of Electrical Engineering, 500 West 120th Street, New York, New York 10027, United States
| |
Collapse
|
22
|
Wang H, Lenglet C, Akkin T. Structure tensor analysis of serial optical coherence scanner images for mapping fiber orientations and tractography in the brain. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:036003. [PMID: 25741662 PMCID: PMC4350401 DOI: 10.1117/1.jbo.20.3.036003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 02/19/2015] [Indexed: 05/05/2023]
Abstract
Quantitative investigations of fiber orientation and structural connectivity at microscopic resolution have led to great challenges for current neuroimaging techniques. Here, we present a structure tensor (ST) analysis of ex vivo rat brain images acquired by a multicontrast (MC) serial optical coherence scanner. The ST considers the gradients of images in local neighbors to generate a matrix whose eigen-decomposition can estimate the local features such as the edges, anisotropy, and orientation of tissue constituents. This computational analysis is applied on the conventional- and polarization-based contrasts of optical coherence tomography. The three-dimensional (3-D) fiber orientation maps are computed from the image stacks of sequential scans both at mesoresolution for a global view and at high-resolution for the details. The computational orientation maps demonstrate a good agreement with the optic axis orientation contrast which measures the in-plane fiber orientation. Moreover, tractography is implemented using the directional information extracted from the 3-D ST. The study provides a unique opportunity to leverage MC high-resolution information to map structural connectivity of the whole brain.
Collapse
Affiliation(s)
- Hui Wang
- University of Minnesota, Department of Biomedical Engineering, Minneapolis, Minnesota 55455, United States
- Address all correspondence to: Hui Wang, E-mail:
| | - Christophe Lenglet
- University of Minnesota, Center for Magnetic Resonance Research, Department of Radiology, Minneapolis, Minnesota 55455, United States
| | - Taner Akkin
- University of Minnesota, Department of Biomedical Engineering, Minneapolis, Minnesota 55455, United States
| |
Collapse
|
23
|
Zhang X, Haynes P, Campbell KS, Wenk JF. Numerical evaluation of myofiber orientation and transmural contractile strength on left ventricular function. J Biomech Eng 2015; 137:044502. [PMID: 25367232 DOI: 10.1115/1.4028990] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Indexed: 11/08/2022]
Abstract
The left ventricle (LV) of the heart is composed of a complex organization of cardiac muscle fibers, which contract to generate force and pump blood into the body. It has been shown that both the orientation and contractile strength of these myofibers vary across the ventricular wall. The hypothesis of the current study is that the transmural distributions of myofiber orientation and contractile strength interdependently impact LV pump function. In order to quantify these interactions a finite element (FE) model of the LV was generated, which incorporated transmural variations. The influences of myofiber orientation and contractile strength on the Starling relationship and the end-systolic (ES) apex twist of the LV were assessed. The results suggest that reductions in contractile strength within a specific transmural layer amplified the effects of altered myofiber orientation in the same layer, causing greater changes in stroke volume (SV). Furthermore, when the epicardial myofibers contracted the strongest, the twist of the LV apex was greatest, regardless of myofiber orientation. These results demonstrate the important role of transmural distribution of myocardial contractile strength and its interplay with myofiber orientation. The coupling between these two physiologic parameters could play a critical role in the progression of heart failure.
Collapse
|
24
|
Wang Y, Zhang K, Wasala NB, Duan D, Yao G. Optical polarization tractography revealed significant fiber disarray in skeletal muscles of a mouse model for Duchenne muscular dystrophy. BIOMEDICAL OPTICS EXPRESS 2015; 6:347-52. [PMID: 25780728 PMCID: PMC4354596 DOI: 10.1364/boe.6.000347] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 01/03/2015] [Accepted: 01/03/2015] [Indexed: 05/14/2023]
Abstract
Optical polarization tractography (OPT) was recently developed to visualize tissue fiber architecture with cellular-level resolution and accuracy. In this study, we explored the feasibility of using OPT to study muscle disease in the mdx4cv mouse model of Duchenne muscular dystrophy. The freshly dissected tibialis anterior muscles of mdx4cv and normal mice were imaged. A "fiber disarray index" (FDI) was developed to quantify the myofiber disorganization. In necrotic muscle regions of the mdx4cv mice, the FDI was significantly elevated and can be used to segment the 3D necrotic regions for assessing the overall muscle damage. These results demonstrated the OPT's capability for imaging microscopic fiber alternations in muscle research.
Collapse
|