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Biomedical subjects

M Belohlavek

Publications and source records attributed to M Belohlavek.

8 recordsLinked to original sources
PubMed1997

Toroidal geometry: novel three-dimensional intracardiac imaging with a phased-array transducer.

Recent advances in small, linear-array transducers have opened new avenues for three-dimensional image acquisition from an intracardiac approach. The purpose of this study was to introduce a novel method of image acquisition using toroidal geometry, explore its fidelity of reproduction of three-dimensional cardiac anatomy, and determine whether a whole-heart scan is achievable. Acquisition was accomplished through 360-degree incremental rotation of a rigid endoscope with a side-mounted ultrasound transducer. The procedure was first tested with the use of a gelatin model to define far-field slice resolution with 1.8-degree rotational increments. Comparison of three-dimensional scans of cardiac specimens with corresponding photographs confirmed that toroidal geometry can provide a high-quality display of structures from all sides. We conclude that whole-heart three-dimensional scanning from within the cardiac chambers is possible with toroidal geometry. The quality of depicted anatomy depends on transducer location within the heart, distance from the transducer, density of slices, and image resolution. The potential of intracardiac three-dimensional ultrasound imaging includes detailed spatial evaluation of cardiac morphology, determination of appropriate placement of investigative or therapeutic devices (catheters, closure devices, etc.), and assessment of cardiac function.

Animals↗
PubMed1997

Detection of cardiac boundaries in echocardiographic images using a customized order statistics filter.

Order statistics filters are nonlinear filters that suppress impulsive and Gaussian noise while preserving edges. These features are particularly useful for cardiac boundary detection in ultrasound images. Based on these facts, we have analyzed performance of a combined ranked order statistics filter. The filter subtracts ranks of ordered highest and lowest intensity values of pixels encompassed in a filter window. The rank extent and window size selection allow adjustment of filter properties for a particular application. Increasing the rank fosters the low-pass characteristics of the filter. Increasing the window size supports noise removal but reduces anatomic selectivity. The filter highlights cardiac boundaries in clinical echocardiograms with intensity proportional to the local probability of a presence of the boundary.

Echocardiography↗
PubMed1995

Congenital heart disease: wide-field, three-dimensional, and four-dimensional ultrasound imaging.

The next significant advance for cardiovascular ultrasound will be the introduction of clinical three-dimensional (3-D) imaging. With increasing computer power and software and hardware, 3-D ultrasound imaging will become a reality over the next few years. Of all cardiovascular abnormalities, congenital heart disease is one of the most logical entities to lend itself to wide-field and 3-D presentation. Tomographic two-dimensional (2-D) echocardiography has in great part replaced cardiac catheterization as the means of accurately visualizing congenital cardiac defects. However, two distinct limitations exist with current 2-D presentations: (1) limited field of view (ie, 90 degrees sector) and (2) tomographic slices that must be assimilated by the examiner into a 3-D or four-dimensional diagnosis. True 3-D imaging has the ultimate capability of rendering anatomy in a format comparable to looking at the actual cardiac specimen. If electronic rendering were really feasible and of suitable quality, one could envision electronically extracting the heart from a living human and examining abnormalities much as one might examine a cardiac specimen (ie, "electronic vivisection"). This article reviews the state of the art of wide-field and 3-D cardiovascular ultrasound in the assessment of congenital heart disease.

Adult↗
PubMed1993

Three-dimensional ultrasound imaging of the atrial septum: normal and pathologic anatomy.

OBJECTIVES: This study investigated the feasibility of producing three-dimensional gray scale ultrasound images of the atrial septum to demonstrate normal and pathologic anatomy. BACKGROUND: Two-dimensional echocardiography is the principal technique used for imaging the atrial septum. Although the diagnostic accuracy of two-dimensional echocardiography is high, its capability for displaying complex three-dimensional relations is limited. METHODS: Three-dimensional ultrasound images were reconstructed from tomographic images obtained during routine transesophageal echocardiographic examinations. Custom-made semi-automatic algorithms for image enhancement, interpolation and segmentation were used to produce volumetric gray scale images. Volume-rendered displays of the atrial septum were generated for analysis. Sequential three-dimensional images were generated through the cardiac cycle and displayed cinematographically to permit assessment of motion. RESULTS: The three-dimensional images obtained from six patients clearly demonstrated normal and pathologic anatomy of the atrial septum, including atrial septal defects, atrial septal aneurysm and aortic valve ring abscess. The images could be manipulated electronically to demonstrate spatial relations and internal structural details. CONCLUSIONS: Three-dimensional gray scale reconstruction of ultrasound images obtained by transesophageal echocardiography is feasible. These images clearly demonstrate anatomic details and spatial relations. The gray scale images may be interactively manipulated to optimize the clinician's visualization of the atrial septum and its associated pathologic conditions.

Cardiomyopathies↗
PubMed1993

Multidimensional visualization in echocardiography: an introduction.

X-ray films depict three-dimensional objects as shadows in a two-dimensional plane; thus, objects become superimposed. Computed tomography and other types of tomographic imaging, such as ultrasonography, acquire two-dimensional images of a material property within a thin slice. Sequential adjacent two-dimensional tomograms can be used to construct three-dimensional displays of objects. Visualization, a field of computer science, enables scientists to measure image attributes (extraction of features), identify features (classification), separate objects from one another (segmentation), and produce comprehensible, information-dense images from three-dimensional data sets (rendering). A three-dimensional rendering of the heart can be used to represent only one component of the heart, such as the atrial septum or the ventricular chamber, and can be shaded or colored to enhance comprehension. Three-dimensional images rendered sequentially over time result in a dynamic four-dimensional display. This report describes multidimensional visualization of objects and tissues and specifically discusses examples from echocardiography.

Echocardiography↗
PubMed1993

Three- and four-dimensional cardiovascular ultrasound imaging: a new era for echocardiography.

Three-dimensional and four-dimensional ultrasonography were pioneered in the 1960s yet have been used little clinically. Only recently have advances in cardiovascular ultrasound equipment and in digital image storage, manipulation, and display techniques made three- and four-dimensional imaging clinically feasible. In this report, we review the historical development of these technologies during 3 decades to their culmination in current state-of-the-art technology. Examples of such multidimensional images are presented, with special emphasis on clinical applications. Although several limitations persist, three-dimensional cardiovascular ultrasonography seems likely to enhance imaging of the heart and vessels in a manner similar to the advent of two-dimensional echocardiography in the M-mode era. Clinician-scientists will soon be able to extract an object, such as the heart, from the body electronically for the purpose of anatomic, functional, and histologic analysis without adverse effect on the patient.

Echocardiography↗
PubMedDate not supplied

Three-dimensional reconstruction of color Doppler jets in the human heart.

A computer algorithm has been developed for segmentation and three-dimensional (3D) reconstruction of Doppler color-flow images. The algorithm enables the user to select a range of velocities, represented by colors, for segmentation and subsequent 3D reconstruction. The reconstructed flows are assigned a color palette and merged with the volume-rendered gray-scale image to produce a 3D image containing both flow and anatomic information. The results demonstrate the application of the algorithm to regurgitant and shunt jets with complex spatial and velocity patterns. We conclude that 3D reconstruction of selected color spectra (e.g., velocities) of Doppler color flows and surrounding anatomy is feasible in the clinical setting.

Algorithms↗