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3D Dynamics Echocardiography. Workstation for the Acquisition, Reconstruction and Visualization of 4D Images of the Heart.
Torrealba Víctor; Bosnjak Antonio; Acuña Manuel; Hernández Lilia; Roux Christian; Montilla Guillermo.Centro de Procesamiento de Imágenes. Facultadad de Ingeniería.
Introduction: Cardiovascular illnesses constitute a problem of public health at world level and they frequently lead to disability and mortality in early and productive stages of life. In Venezuela, they are the greatest cause of death among people whose ages range between 25 and 64 years .
At the present time, the ultrasound is the best diagnosis method of cardiovascular illnesses. Using this method, specialist doctors obtain space-temporary information of the heart. 3D geometry of the heart is obtained by means of a mental reconstruction of video images of 2D echoes, which are observed in movement at different slices planes. This methodology is subjective and it is highly susceptible to errors. It requires a great knowledge of the anatomy of the heart by the cardiologist to obtain an exact interpretation of the images of 2D echoes.
At this moment, there are hardware echocardiography equipments and grabber systems also exist for visualizasing 4D images of the heart. Regrettably the costs of these equipments are very high and in countries like Venezuela which is currently having financial problems, its acquisition so much at public level as private is limited.
Objectives: A Workstation was developed for the acquisition, reconstruction, processing and visualization of 4D images of the heart. These images were obtained from two-dimensional echocardiography equipments using the method of transtoracic rotational sweep.
Methodology. One important step to the reconstruction of 4D images of the heart, is to build an echocardiography database. This is generally obtained by scanning the heart with the ultrasound sheaf; In this work, we used the method of Transtorasic Rotational Fan . In this method, the transducer is rotated on its longitudinal axis (See figure 1).
Figure 1. Transtoracic rotational sampling, apical see.a) Position and
movement of the transducer.
b) Two-dimensional Echo obtained on the slice plane 1.c) Volume swept by the ultrasonic sheaf.
To obtain a sequence of 4D-data of the heart, we used a commercial two-dimensional echocardiography equipment, but the processes involved are complicated. This is because the volumetric images should be generated during the heart cycle, they should be obtained starting from 2D echoes captured in different times and in different planes of acquisition. Additionally, there are diverse anatomical events that generate spatial noise and the elimination of small anatomical detail during the 4D-data acquisition can also produce errors. These inaccuracies can degenerate the reconstructed image. The description of these problems and their solution, are explained in detail by authors in previous works [2,3,4]. In summary, the acquisition of data was synchronized with the breathing rhythm and the heart rhythm; the manipulation of the ultrasonic transducer was realized by a motorized servo-mechanism controlled by computer. We also developed a graphic processing system that allowed the control of the whole station, the processing and visualization of the 4D-database. The figure 2 shows a scheme of the designed Workstation. The ultrasonic test is realized in real time using a two-dimensional echographic ESOATE PARTNER model AU-3 with a sectoral multifrequency transducer of 3,5/5.0 MHz.
Figure 2. A scheme of the designed Workstation
Results: The figure 3, figure 4 and figure 5 show some 3D images obtained with the Workstation developed. The 3D dynamic sequences obtained with the Workstation is on the internet address: http://echocardiography.spedia.net .
Figure 3. Three-dimensional Image of an aortic bi-valve. To the left
in dyastole and to the right in systole. It is appreciated an augment
of the border of the valves and the complete opening of the same ones.
Figure 4. Sequence 3D. See of three-dimensional four
cameras in which is appreciated in detail the left ventricle
Figure 5. Image three-dimensional view from the interior
of the left
ventricle toward the mitral valve. To the left in dyastole and to the
right in systole. They are appreciated the exit tract and the tract of
entrance of the left ventricle simultaneously.
This Workstation was installed in a Cardiology Consulting Room of the Image Processing Center at University of Carabobo. We conducted 15 echocardiographics exams, (10 children and 5 adults), the patients' ages ranged between 7 and 45 years. In all we had taken 60 radial slices of the heart anatomy and the frames quantity stored during the cardiac cycle varied between 13 and 16 frames. The time for each exam varied between 22 and 35 minutes. Initially an engineer and a medical cardiologist, both members of the Workstation design team were present during the capture of sequences of each test. The operation of the Workstation is simple, hence it can be used by the cardiologist without technical support.
Conclusions: A Workstation for the acquisition, reconstruction, processing and visualization of 4D images of the heart has been presented. It uses images generated from two-dimensional echocardiographic equipments using the method of transtoracic rotational sweep.
The obtained results are highly satisfactory. The 4D images of the heart obtained using the Workstation were of high quality; it shows the details of the heart cavities and the valvular structure. From the clinical point of view this acquires great importance since the medical exam is simple and non-invasive. Moreover, it doesn't need sophisticated equipments, and it can be installed in a consultory. Additionally, we have obtained objective data from the heart anatomy. These images can be a useful guide for the cardiovascular surgeon.
The cost of this Workstation is much less since it was implemented using existing medical technology and the software was developed on a personal computer (PC). This system is a viable alternative in developing countries where there is limited financial resources and necessary technology in cardiology is non existent.
 M.S.A.S. Ministerio de Sanidad y Asistencia Social. Anuario Epidemiológico y
Estadística Vital. Venezuela. 1995.
 Torrealba Víctor, Acuña M., G. Montilla, L. Hernández, A. Bosnjak, C. Roux. " Ecocardiografía Dinámica Tridimensional. Estación de Trabajo para la Adquisición, Reconstrucción y Visualización de Imágenes 4D del Corazón. Utilizando el Método de Barrido Rotacional Transtorácico ". http://members.xoom.com/_XOOM/vtorreal/trabajos/estacion4d/ecocardi.htm
 Víctor Torrealba, Manuel Acuña, Lilia Hernández, Guillermo Montilla, Antonio Bosnjak, Christian Roux. " Ecocardiografía Dinámica Tridimensional . Adquisición y Reconstrucción de Imágenes 4D del Corazón, Utilizando el Método de Abanico Manual Transtorácico. " < http://members.xoom.com/_XOOM/vtorreal/trabajos/abanico/adquisic.htm >
 Víctor Torrealba, Lilia Hernández, Manuel Acuña, Guillermo Montilla, Antonio Bosnjak, Christian Roux. "Detección del Ritmo Respiratorio Utilizando el Método de Pletismografía de Impedancias".< http://members.xoom.com/_XOOM/vtorreal/trabajos/respira/respira00.htm >
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