Biomedical subjects

A S Gopal

Publications and source records attributed to A S Gopal.

23 records · Page 2Linked to original sources

PubMed1992

Reversible pulmonary artery obstruction in a patient with bronchogenic carcinoma. Diagnosis by two-dimensional and Doppler echocardiography.

Neoplastic invasion of the pulmonary arteries, although common, rarely results in obstruction to right ventricular outflow. We report an unusual case of severe pulmonary hypertension, right ventricular dilatation, and righ ventricular dysfunction resulting from pulmonary arterial compression by bronchogenic carcinoma. The diagnosis was made by two-dimensional and Doppler echocardiography and supported by computed tomographic findings. Echocardiography was used to follow the patient's response to therapy and documented the subsequent resolution of pulmonary arterial obstruction.

Carcinoma, Bronchogenic↗

PubMedDate not supplied

Three-dimensional echocardiography: limitations of apical biplane imaging for measurement of left ventricular volume.

A new three-dimensional echocardiographic system creates a "line of intersection" display to allow precise and known positioning of echocardiographic images. Our purpose was to determine whether use of the line-of-intersection display will improve positioning of the apical four-chamber and apical two-chamber views and thereby improve the agreement between estimates of left ventricular volume by apical biplane echocardiography and cineventriculography. Unguided and line of intersection-guided apical biplane views were obtained in 31 patients immediately before cardiac catheterization and single-plane cineventriculography. In 15 patients the line-of-intersection display was used to measure the position of the image plane in studies of unguided and guided methods. Linear regression and limits of agreement analysis were used to assess the agreement between cineventriculographic volumes and echocardiographic volumes determined from each set of images. The Wilcoxon test was used to compare guided and unguided image positioning. The line-of-intersection display improved four-chamber and two-chamber view positioning closer to the center of the ventricle and rotation closer to orthogonal positioning. Guided-image positioning was not able to correct displacement of the ultrasound beam anterior to the ventricular apex without deterioration of image quality in most patients. Despite improvements in image plane positioning, the agreement between echocardiographic and cineventriculographic volumes was unchanged. For end-diastole views, the unguided images had an r value = 0.84, standard error of the estimate of +/- 23.0 cc, and limits of agreement of +/- 62.4 cc. Corresponding values for the guided images at end diastole were r = 0.85, standard error of the estimate of +/- 22.9 cc, and limits of agreement of +/- 60.8 cc. At end systole the unguided results were r = 0.91, standard error of the estimate of 16.8 cc, and limits of agreement of +/- 52.2 cc. The line-of-intersection guiding of image plane positioning can improve apical image positioning but does not improve the agreement between apical biplane echocardiographic and cineventriculographic left ventricular volumes. The optimal apical imaging window is frequently occluded by the rib cage, resulting in a decrease in image quality. This reduction of image quality, combined with assumptions of left ventricular geometry, limit the accuracy of estimates of left ventricular volume from apical biplane echocardiography.

Adult↗

PubMedDate not supplied

Three-dimensional echocardiography: in vitro validation for quantitative measurement of total and "infarct" surface area.

The rapid development of numerous therapeutic options for myocardial revascularization requires more advanced, quantitative echocardiographic methods such as measurement of total endocardial and infarct surface area to evaluate myocardial infarction and assess the effects of therapy. Two-dimensional echocardiography is insufficiently quantitative for this purpose because it cannot directly measure three-dimensional relationships with such as volume and surface area. To limitation this limitation we have developed a three-dimensional echocardiograph capable of measuring total and regional or "infarct" surface area. In vitro validation of this method has been carried out comparing computed areas with true areas of a pin model and fixed hearts. Infarcts were demarcated on the fixed hearts by placing pins in the myocardium. The pin heads on the epicardial surface defined infarct regions that could be imaged. True surface areas of the pin model were determined by physical measurement and calculation. True areas of the fixed hearts were determined by planimetry of surface casts made with plastic tape. Accuracies for total and infarct areas were 1.36% and 2.13% for the pin model and 1.61% and 3.48% for the fixed hearts. Interobserver variability for both phantoms was less than 2.5%. The standard error of the estimate predicting total and infarct surface area for the fixed hearts was 1.53 cm2 and 0.71 cm2, respectively (p < 0.001). Three-dimensional echocardiography provides a new, accurate method for directly measuring global and regional surface areas and holds promise for improved evaluation of myocardial infarction and assessment of its treatment.

Animals↗

PubMedDate not supplied

Ultrasound beam orientation during standard two-dimensional imaging: assessment by three-dimensional echocardiography.

Standard two-dimensional echocardiographic image planes are defined by anatomic landmarks and assumptions regarding their orientation when these landmarks are visualized. However, variations of anatomy and technique may invalidate these assumptions and thus limit reproducibility and accuracy of cardiac dimensions recorded from these views. To overcome this problem, we have developed a three-dimensional echocardiograph consisting of a real-time scanner, three-dimensional spatial locater, and personal computer. This system displays the line of intersection of a real-time image and an orthogonal reference image and may be used to assess actual image orientation during standardized two-dimensional imaging when the line-of-intersection display is not observed by the operator. Three hundred forty standard images were assessed from 85 examinations by 11 echocardiographers. Twenty-four percent of the unguided standard images were optimally positioned within +/- 5 mm and +/- 15 degrees of the standard. Of the optimal images, two thirds were parasternal long-axis views. A subsequent study with three-dimensional echocardiography and line-of-intersection guidance of image positioning showed 80% of the guided images to be optimally positioned, a threefold improvement (p < 0.001). Two-dimensional echocardiography does not achieve reasonably consistent optimal positioning of standard imaging views, suggesting that measurements taken from these views are likely to be suboptimal. Three-dimensional echocardiography that uses line-of-intersection guidance improves image positioning threefold and should therefore improve the accuracy and reproducibility of quantitative echocardiographic measurements derived from these images.

Adolescent↗

PubMedDate not supplied

Three-dimensional echocardiographic volume computation by polyhedral surface reconstruction: in vitro validation and comparison to magnetic resonance imaging.

Two-dimensional echocardiographic methods of left ventricular volume computation are limited by geometric assumptions and image plane positioning error in the nonvisualized dimension. We evaluated a three-dimensional (3D echocardiographic method that addresses these limitations. Our method uses a volume computation algorithm based on polyhedral surface reconstruction (PSR) and nonparallel, unequally spaced, nonintersecting short-axis planes. Seventeen balloon phantoms were subjected to volume computation by the 3D echocardiography-PSR method and by magnetic resonance imaging (MRI) and compared to true volumes determined by water displacement. The results for 3D echocardiography-PSR were: accuracy = 2.27%, interobserver variability = 4.33%, r = 0.999, SEE = 2.45 ml, and p less than 0.001. Results for MRI were 8.01%, 13.78%, r = 0.995, SEE = 7.01 ml, and p less than 0.001. There was no statistically significant difference between the methods. We conclude that precise image plane positioning and use of the 3D echocardiographic-PSR volume computation method achieves high accuracy and reproducibility in vitro. The excellent in vitro correlation between 3D echocardiography-PSR and MRI indicates that MRI may also serve as an in vivo standard of comparison.

Cardiac Volume↗