Search PubMed⌕ Search

Biomedical subjects

E A Geiser

Publications and source records attributed to E A Geiser.

At least 37 records · Page 2Linked to original sources
PubMed1984

Evaluation of a three-dimensional reconstruction to compute left ventricular volume and mass.

This study tests the accuracy of a model to calculate left ventricular volume (LVV) and muscle volume (MV) when optimal data were used. These volumes were calculated using endocardial and epicardial borders traced from photos of cross sections of 20 animal (dog, goat and pig) hearts. A pyramid summation algorithm was used to perform a 3-dimensional (3-D) reconstruction based on 5 short-axis views, thus providing computer volume estimates. These were compared with the true (T) ventricular volumes determined by water filling of the cavity and the true MV based on weight. Because each heart was sliced in 5 planes, the appropriateness of the algorithm for MV could be tested for 6 regions. The pyramid summation algorithm consistently underestimated MV at the base and apex, but was accurate from the midmitral valve to the inferior papillary muscle region. Consequently, the total MV was computed as the midventricular MV, plus base and apex volumes computed from regression equations. Results showed that 3-D reconstruction resulted in a regression of LVVT = 1.02LVV3D + 10.30 ml with r = 0.987 for the chamber of MVT = 1.05 MV3D - 9.78 ml, with r = 0.967. It is concluded that the pyramid summation algorithm can accurately estimate volumes from spatially registered short-axis data with 95% prediction limits about the mean of the data of +/- 10 ml for left ventricular chamber volume and +/- 17.6 ml for MV.

Animals↗
PubMed1984

In vitro analysis of boundary identification techniques used in quantification of two-dimensional echocardiograms.

Echocardiographic cross-sectional areas of 10 formalin-fixed animal left ventricles were determined by 5 independent observers using black-white (B-W) and mid-spot (M-S) endocardial boundary identification techniques. The echocardiographic cross-sectional areas were compared with the true anatomic cross-sectional areas of the same 10 hearts to determine the accuracy, variability and reliability of each technique. The results of these comparisons revealed that the M-S technique was more accurate than the B-W technique (3.3 +/- 7.2 vs 34.9 +/- 8.6% error). However, the B-W technique was more reliable in that it had a smaller interobserver and estimated intraobserver variability. The M-S technique had a 6% greater intraobserver variability.

Animals↗
PubMed1984

Computer-assisted edge detection in two-dimensional echocardiography: comparison with anatomic data.

Four methods of computer-based edge detection were evaluated for identification of endocardial and epicardial borders on 2-dimensional echocardiograms of excised hearts. A method was also evaluated for observer identification of cardiac borders in the same hearts. The accuracy of computer-derived borders and of observer-derived borders were determined by comparison to anatomic borders measured from photographs of slices of the excised hearts. Echocardiographic borders were compared with anatomic borders by calculation of segmental cavity areas and wall thickness. Each of the methods tested (computer and observer) identified endocardial borders accurately, resulting in cavity segment areas that correlated well with the corresponding anatomic data (r = 0.90 to 0.92). Regional wall thicknesses correlated less well with anatomic data (r = 0.74 to 0.80), suggesting that endocardial borders were identified more accurately than were epicardial borders. Thus, the methods of computer-assisted echocardiographic border detection tested identified the endocardium and epicardium as accurately as a trained observer evaluating unprocessed echocardiograms. Computer-based methods of border detection may be useful in the automated analysis of clinical echocardiograms.

Animals↗
PubMed1984

Echocardiographic evaluation of responses to left ventricular volume loading by principal components and nomographic analysis.

Changes in performance of left ventricles (LV) with volume overloads are difficult to determine by conventional clinical methods. This information, however, is important for the proper timing of therapeutic interventions to preserve LV function. Seven size-adjusted (by regression with end-diastolic diameter, EDD) LV performance parameters from 100 normal echocardiograms (echos) were entered into a principal component analysis (PCA). Two factors (linear combination of the 7 parameters) were obtained from the analysis. Prediction limits (95%) about these two factors used in combination, correctly classified 92% of the normal echos. More detailed analysis of the two PCA factors revealed that the majority of the variability within the factors was explained by size-adjusted parameters resultant from the EDD posterior wall (factor 1) and EDD septal excursion (factor 2) regressions, respectively. Plots of the 95% prediction limits about these two regression lines provided nomograms. These nomograms used in combination, correctly classified 95% of the normal echos. When the performance parameters of 64 volume loaded ventricles were evaluated by PCA, four groups were identified. Ten ventricles (16%) were hypokinetic, 29 (45%) were hyperkinetic, 23 (36%) were nomokinetic, and 2 (3%) could not be classified. These classifications were supported by significant between group differences of shortening fraction, velocity of circumferential shortening, and velocity of circumferential expansion. Nomographic classification of the same volume loaded hearts was in excellent (94%) agreement with PCA classification. Nomographic analysis (derived from the PCA) is offered as a less complex, more clinically applicable echo method for evaluating LV performance of volume loaded hearts.

Adolescent↗
PubMed1982

A mechanical arm for spatial registration of two-dimensional echocardiographic sections.

The accurate calculation of left ventricular (LV) wall motion from two-dimensional echocardiographs will require the accurate registration of the position from which each two-dimensional (2-D) view was obtained. This paper describes a mechanical arm with five degrees of freedom that was developed so that the position and orientation of 2-D echo sections could be calculated in three-dimensional space. High precision potentiometers, direct or gear driven, permit calibration and measurement of each of the five movements. Using the length of the arm and the angles measured by these potentiometers, the position of a 2-D section can be calculated with respect to a fixed reference point outside the body. The measurement arm was extensively retested after six months of clinical use. In patient studies, 95% confidence interval for positioning a cross-section of the long axis is +/- 6 mm. This error is similar to the cross-plane resolution to most contemporary two-dimensional transducers. On the basis of an extensive analysis of variance, recommendations are made to improve the accuracy of the arm.

Echocardiography↗
PubMed1982

Effects of carbon dioxide, Nd-YAG, and argon laser radiation on coronary atheromatous plaques.

Laser radiation has been successfully applied in several areas of medical practice. However, its use in cardiology and specifically its effects on obstructive atherosclerosis have largely been unexplored. To evaluate effects of laser radiation on atherosclerotic plaques 25 fresh necropsy atherosclerotic coronary artery segments were exposed to laser radiation with either a carbon dioxide, Nd-YAG, or argon laser. Split or intact segments were prepared under dry conditions or while immersed in saline solution or blood and exposed to laser radiation as power and duration of exposure varied. All 3 lasers were capable of creating controlled injury to atherosclerotic plaques. In general, the magnitude of injury varied according to the total energy delivered (that is, power times duration of exposure. Calcified and noncalcified plaques were penetrated with similar levels of injury. Histologic examination demonstrated that laser radiation produced a wedge incision in the atherosclerotic plaque which was surrounded by zones of thermal and acoustic injury.

Argon↗
PubMed1980

Vascular load defined by the aortic input impedance spectrum.

The load that the arterial system places upon the myocardium during ventricular ejection is of primary importance in the consideration of ventricular function. This dynamic load can be characterized by the total aortic input impedance spectrum obtained from Fourier analysis of pulsatile pressure and flow waves recorded in the ascending aorta. Certain indices derived from the impedance spectrum provide quantitative and qualitative information about this dynamic load in terms of peripheral arteriolar dimensions (resistance), aortic wall stiffness (compliance), and wave reflections (reflectance). Studies in isolated heart preparations and intact dogs have shown that increases in resistance (decrease in arteriolar caliber) or aortic stiffness (decrease in aortic compliance) independently influence an increase in peak left ventricular pressure and a decrease in stroke volume. An increase in wave reflections also has the potential to reduce stroke volume while increasing peak pressure. Recent human studies have shown that in heart failure patients the components of the dynamic vascular load are also elevated compared to subjects without heart failure. Infusion of the vasodilator sodium nitroprusside abruptly reduces these components of vascular load as ventricular stroke output is enhanced. Thus, there is sufficient evidence to indicate that changes in the mechanical properties of the arterial tree influence the opposition to ventricular outflow. Since these properties can be described by the aortic input impedance spectrum, this function can be used to define the external load imposed on the ventricle by the vascular system.

Animals↗
PubMed1975

The left ventricle in anomalous pulmonary venous return. Morphometric analysis of 36 fatal cases in infancy.

The mass of the left ventricle is normal in infants with total anomalous pulmonary venous return, but the ventricular cavity is compromised by leftward displacement of the interventricular septum due to the combined pressure-volume overload of the right side of the heart. Severe septal displacement is associated with distorted myocardial architecture in the region of the septal attachments of the left ventricular free wall. Abnormalities of septal motion are frequently detected in echocardiograms. Left ventricular output is low, as judged by arrested development of the aortic valve circumference, and is probably compromised both by the left to right shunt and by septal displacement. Successful correction of the anomaly may depend on intervention before the changes in septal position, structure, and function have become irreversible.

Cardiac Output↗
PubMedDate not supplied

A method for evaluation of enhancement operations in two-dimensional echocardiographic images.

A means of estimating the degree of enhancement of structure and suppression of background noise in filtered two-dimensional echocardiographic images is described. The method is termed the peak-to-background ratio. To test the method, two-dimensional short-axis echocardiographic images were enhanced with Laplacian operations of increasing mask size. There was excellent correlation between the calculated peak-to-background ratio and the subjective opinion of trained echocardiographers. Furthermore, radial length measurements made from images that were thought to be optimally enhanced by the peak-to-background ratio calculation showed the lowest interobserver mean differences. We conclude that the peak-to-background ratio does reflect improvement in characteristics of the image that favor more precise measurement (amplification of peaks and suppression of background) and can be used to help guide a dynamic approach to image processing.

Analog-Digital Conversion↗
PubMedDate not supplied

Applications of cross-correlation techniques to the quantitation of wall motion in short-axis two-dimensional echocardiographic images.

Echocardiography is now a mainstay in the diagnosis of cardiovascular disease. Rapid methods for quantitation of the images would provide an effective tool for the diagnosis of change in left ventricular function. The purpose of this article is to show the feasibility of using the cross-correlation technique to quantify change in left ventricular function over time in two-dimensional short-axis echocardiographic images. Radial histograms of radial distance versus the number of probable specular targets are formed in eight sectors on each frame during the cardiac cycle. These histograms are then shifted to a position of best correlation. The number of radial bins through which the histograms at end systole are shifted to correlate with those of the frame at end diastole defines the regional motion. The methods are described and preliminary findings are presented.

Algorithms↗