Echocardiography

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Recent advances in echocardiography, in particular, the emergence of 3D echocardiography, have encouraged studies of the shape and geometry of non-visualized cardiac structures, such as the annuli. The 3D shape and geometry of the bicaspid valve in the normal population and in cardiac patients had been revealed in detail with 3D echocardiography by several previous studies. Even before the emergence of the 3D echocardiography, the 3D shape and the function of the bicaspid during cardiac cycle had been explored and uncovered with other 3D imaging techniques. Annular geometry changes during systole. It is generally accepted that the annular size increases during the latter half of systole after presystolic narrowing of the annulus, and then continues to increase in size from early diastole and reaches a maximum during late diastole. During the process of 3D image acquisition and 3D reconstruction, several limitations were evident. to obtain a 3D reconstruction of a non-visualized cardiac structure, the anatomical reference markers should be defined prior to reconstruction in order to obtain the correct anatomical orientation. Unfortunately this work can only give us a 3D reconstructed images of bicuspid and tricuspid valves but not the relationship to the cavities during the cardiac cycle. Newly developed techniques like laser dissection microscopy in combination with quantitative PCR or mass spectrometry can be used to obtain these estimates. Because of its small size and intricate morphology, it is very laborious to apply these techniques to the developing heart. High-throughput techniques such as serial analysis of gene expression (SAGE) and microarrays provide genetic expression data, but these are devoid of spatial information. The use of staining techniques for mRNA and protein, in situ hybridization (ISH) and immunohistochemistry, respectively, enable the localization of specific mRNA and proteins in tissues with cellular resolution. Combining these staining methods with radioactive probes and autoradiography permits the calibration and subsequent quantification of the staining intensity (Jonker A 1997, Ruijter JM 2001). For organs that are reasonably "amorphous" and composed of isotropic tissue, such as the liver, a limited number of sections can provide a quantitative estimation of gene expression gradients (J. M. Ruijter, J. Hagoort, M. M. Markman, R. G. Gieling, and W. H. Lamers, unpublished observations). However, for organs such as the developing heart, a few random sections would not suffice; the spatial distribution of the specific gene product throughout the whole organ must be mapped. Three-dimensional (3D) reconstructions of embryonic development were originally based on computeraided manual tracing of the organs of interest (Huijsmans DP 1986, Verbeek FJ 1995), and the reconstructed organs were illustrated by medical artists. With the advent of digital cameras, reconstruction methods based on digitized images have become commonplace. A full review of past reconstruction methods would do no justice to those researchers who had to implement their reconstruction protocols with the hardware and software available at that time. Recently, methods were published based on episcopic image capturing (Ewald AJ 2002, Weninger WJ 2002). These episcopic methods, which acquire an image just before sectioning, enable one to accurately obtain aligned high-resolution digital stacks, based on fluorescence.

In a work by (Alexandre T. Soufan,2003)The myocardium and the cardiac lumen of a developmental series of mouse embryos was mapped and reconstructed using their protocol. The myocardium of the heart is defined as the structure that stains with a mix of myocardium-specific mRNA probes using the nonradioactive ISH method. T he appearance of the reconstructions shows that hearts from the same embryonic day are virtually identical. Two or three reconstructions of the same embryonic day will probably suffice to obtain a representative reconstruction of that developmental stage. The morphology of the reconstructions closely resembles that seen in whole mount-stained hearts The volume data extracted from the duplicate hearts differ by a maximum of 10%. This "preliminary" biological result indicates that the biological variation may not pose a problem for generalized use of this series. Note that these volumes have been obtained using the Cavalieri principle and are therefore unbiased estimates of the myocardium volumes (Howard CV 1998). Therefore, these volumetric data of the developing heart structures can be used in mathematical and functional models of heart development. One can calculate from these data that the myocardium volume increases 100 times in 6 days (between ED 8.5 and 14.5). Assuming that all cells present in the heart do divide in that period, this volume increase would correspond to 6.6 cell divisions, which is at least one division of each cell every 24 h. However, from literature (Cluzeaut F 1986, Thompson RP 1990) and data obtained from quantitative reconstructions (Soufan AT 2001), we know that myocardial cells differ in cell-cycle duration within hearts and between hearts of different stages. The increase in volume may not only be explained by mitoses, but other mechanisms, such as cellular growth, cell migration, and transdifferentiation (recruitment) have to be taken into account as well. Therefore, an accurate description of the developing heart in dynamics during all stages of development will benefit from data obtained by quantitative and volumetric computer 3D reconstructions.

The past application of the principles of muscle mechanics to the analysis of left ventricular contraction (FRY, D. L., GHIGGS. 1964, Ross, J., JR., COVELL,1966, LEVINE, H. J.,1964) has focused attention upon the need for detailed information concerning the anatomy of ventri cular contraction. At present, many gaps exist in our knowledge of the changes in configuration of the muscular walls, the orientation of muscle fibers and the dimensions of the sarcomeres that occur continuously in the ventricle during the cardiac cycle. Such information is essential to the construction of appropriate geometric models for application in echanical analyses of ventricular contraction and also should provide basic insight into correlations between cardiac structure and function in the normal and the abnormal heart. Studies of the external and internal dimensions of the in situ left ventricle by dimension gauges and angiography have provided much important information concerning changes in the shape and volume of the left ventricle during the cardiac cycle, and studies in the isolated papillary muscle and excised left ventricle have investigated relations between sarcomere dimensions, muscle length, and the volume of the passive heart (SPOTNTTZ, H. M.,1966, HORT, W.1960). So far, however, there has been no correlative examination of gross anatomy and ltrastructure in the contracting left ventricle under known hemodynamic conditions. In the work there were a methods described for rapid fixation in systole or diastole have permitted an analysis of the geometry of the ventricular cavity and wall under known hemodynamic conditions. Information gained by the use of these direct measurements and from other, dynamic techniques, should allow the development of appropriate geometrical models for application in analyses of the mechanical properties of ventricular contraction. Changes in ventricular shape, volume, and wall thickness require a continuously variable model which, when correlated with pressure and flow determinations, should eventually permit precise calculation of stress distribution and fiber shortening throughout the cardiac cycle. Further studies will be undertaken on these ventricles to study the important problem of changes in muscle fiber orientation and distribution that occur across the ventricular wall during diastole and systole. But fully to be able to analyze geometry the beneficial would be to reconstruct in 3D and to compaire it during all stages not only post natal but prenatal development ,which was difficult to do at that time.

Since the morphogenetic changes of the heart occur three-dimensionally, it is essential to visualize and analyze heart development in three dimensions. Three-dimensional visualization is also a powerful tool in embryological study and greatly helps us to understand the dynamic morphogenetic movements in the embryo (Yamada et al., 2006). From the early days of human embryology, attempts were made to visualize embryonic structure in three dimensions. Traditionally, 3D reconstruction of embryonic structures used to be made from serial histological sections of embryos, often with the wax plate technique (Born, 1883). However, such reconstruction and drawing methods require an enormous time and special skills and which very volublein a research. Recent advancement in computer science has made computer-assisted reconstruction of biological structures more effectively. Various 3D structures have been reconstructed by this method, and the reconstructed images can be manipulated as desired on the viewing screen. In the area of the developmental study of the heart and great vessels, computer-assisted reconstruction and computer graphics (CG) have been used to visualize the developing heart and vessels of the mouse (Smith, 2001; Schneider et al., 2003), chick (Hiruma and Hirakow, 1995), and human (DeGroff et al., 2003; Abdulla et al., 2004). In mice, the 3D sequential images of the developing heart have been made between E8.5 and E14.5 (Soufan et al., 2003).

In the present study,there were attampes made in reconstruction of the heart and great vessels of staged human embryos with the aid of computer software and compared their luminal structures of embryos. They showed that computer-assisted reconstruction is a useful and powerful tool for analyzing detailed 3D phenotypes in embryos. During embryonic development, dynamic morphogenetic changes occur in a spatially and temporally coordinated manner. The cardiovascular system is one of the organ systems that undergo drastic morphogenetic movements. The sequential changes of the heart and great vessels in human embryos used to be examined by observing histological sections and wax plate models reconstructed from serial sections (Congdon, 1922; Streeter, 1948), which contributed significantly to human embryology and have been well cited by subsequent embryologists (Cooper and O'Rahilly, 1971; O'Rahilly, 1971). In there study using computer-assisted reconstruction of the heart and great vessels of externally normal embryos largely confirmed the results of those classical reports, although some discrepancies were noted.

In the work (SHIGEHITO YAMADA, 2007) reconstruction of the luminal structure of the hearts and great vessels of staged human embryos from serial histological sections to demonstrate their sequential morphological changes in three dimensions. Anatomical structures were analyzed with a use of 3D images.Not much of information was giving to luminal structure and their volumetric and morphological changes during heart development.

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