Donald L. King

Assessment of cardiac function by three-dimensional echocardiography compared with conventional noninvasive methods.

BACKGROUNDnReliable, serial, noninvasive quantitative estimation of left ventricular ejection fraction is essential for selecting and timing therapeutic interventions in patients with heart disease. Equilibrium radionuclide angiography is widely used for this purpose but has well-recognized limitations. Advantages of echocardiography over equilibrium radionuclide angiography include assessment of wall motion, valvular pathology, and cardiac hemodynamics, in addition to portability, lack of radiation exposure, and substantially lower cost. However, conventional echocardiographic techniques are limited by geometric assumptions, image positioning errors, and use of subjective visual methods. To overcome these limitations, a three-dimensional echocardiographic method was developed. This study compares ejection fraction by three-dimensional echocardiography, quantitative two-dimensional echocardiography, and subjective two-dimensional echocardiographic visual estimation with that by equilibrium radionuclide angiography.nnnMETHODS AND RESULTSnFifty-one unselected patients with suspected heart disease underwent left ventricular ejection fraction determination by equilibrium radionuclide angiography and three-dimensional echocardiography using an interactive line-of-intersection display and a new algorithm, ventricular surface reconstruction, for volume computation. In 44 patients, ejection fractions were also estimated visually by experienced observers from two-dimensional echocardiography and by quantitative two-dimensional echocardiography using an apical biplane summation-of-disks algorithm. An excellent correlation was obtained between three-dimensional echocardiography and equilibrium radionuclide angiography (r = .94 to .97, SEE = 3.64% to 5.35%; limits of agreement, 10.3% to 13.3%) without significant underestimation or overestimation. SEE values and limits of agreement were twofold to threefold lower than corresponding values for all two-dimensional echocardiographic techniques. In addition, interobserver variability was significantly lower for the three-dimensional echocardiographic method (10.2%) than for the apical biplane summation-of-disks method (26.1%) and subjective visual estimation (33.3%).nnnCONCLUSIONSnDetermination of ejection fraction by three-dimensional echocardiography yields results comparable to those obtained by equilibrium radionuclide angiography and is substantially superior to all two-dimensional echocardiographic methods. Therefore, three-dimensional echocardiography may be used for accurate serial quantification of left ventricular function as an alternative to equilibrium radionuclide angiography.

Left ventricular volume and endocardial surface area by three-dimensional echocardiography: Comparison with two-dimensional echocardiography and nuclear magnetic resonance imaging in normal subjects☆

OBJECTIVESnWe evaluated a three-dimensional echocardiographic method for ventricular volume and surface area determination that uses polyhedral surface reconstruction. Six to eight nonparallel, unequally spaced, nonintersecting short-axis planes were positioned with a line of intersection display to overcome limitations associated with two-dimensional echocardiography.nnnBACKGROUNDnTwo-dimensional echocardiographic methods of ventricular volume and surface area determination are limited by assumptions about ventricular shape and image plane position.nnnMETHODSnLeft ventricular end-diastolic and end-systolic volumes and endocardial surface areas determined by three-dimensional echocardiography and nuclear magnetic resonance (NMR) imaging were compared in 15 normal subjects (7 men, 8 women, aged 23 to 41 years, body surface area 1.38 to 2.17 m2). Ten of these subjects also underwent two-dimensional echocardiography; and end-diastolic and end-systolic volumes were determined by the apical biplane summation of discs method and compared with results of NMR imaging.nnnRESULTSnInterobserver variability was 5% to 8% for three-dimensional echocardiography and 6% to 9% for NMR imaging. Both methods were in close agreement on end-diastolic volume (r = 0.92, SEE = 6.99 ml) and end-systolic volume (r = 0.81, SEE = 4.01 ml) and on end-diastolic surface area (r = 0.84, SEE = 8.25 cm2) and end-systolic surface area (r = 0.84, SEE = 4.89 cm2). Three-dimensional echocardiography and NMR imaging correlated significantly better for end-diastolic volume (r = 0.90, SEE = 7.0 ml) and end-systolic volume (r = 0.88, SEE = 3.1 ml) than did two-dimensional echocardiography and NMR imaging (r = 0.48, SEE = 20.5 ml for end-diastolic volume; r = 0.70, SEE = 5.6 ml for end-systolic volume).nnnCONCLUSIONSnThree-dimensional echocardiography is an in vivo method of measuring left ventricular end-diastolic and end-systolic volumes and endocardial surface area with results comparable to those of NMR imaging. Additionally, three-dimensional echocardiography is superior to the two-dimensional echocardiographic apical biplane summation method because the technique eliminates geometric assumptions and image plane positioning error.

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.

Comparison of two- and three-dimensional echocardiography with cineventriculography for measurement of left ventricular volume in patients

OBJECTIVESnWe compared two- and three-dimensional echocardiography with cineventriculography for measurement of left ventricular volume in patients.nnnBACKGROUNDnThree-dimensional echocardiography has been shown to be highly accurate and superior to two-dimensional echocardiography in measuring left ventricular volume in vitro. However, there has been little comparison of the two methods in patients.nnnMETHODSnTwo- and three-dimensional echocardiography were performed in 35 patients (mean age 48 years) 1 to 3 h before left ventricular cineventriculography. Three-dimensional echocardiography used an acoustic spatial locator to register image position. Volume was computed using a polyhedral surface reconstruction algorithm based on multiple nonparallel, unevenly spaced short-axis cross sections. Two-dimensional echocardiography used the apical biplane summation of disks method. Single-plane cineventriculographic volumes were calculated using the summation of disks algorithm. The methods were compared by linear regression and a limits of agreement analysis. For the latter, systematic error was assessed by the mean of the differences (cineventriculography minus echocardiography), and the limits of agreement were defined as +/- 2 SD from the mean difference.nnnRESULTSnThree-dimensional echocardiographic volumes demonstrated excellent correlation (end-diastole r = 0.97; end-systole r = 0.98) with cineventriculography. Standard errors of the estimate were approximately half of those of two-dimensional echocardiography (end-diastole +/- 11.0 ml vs. +/- 21.5 ml; end-systole +/- 10.2 ml vs. +/- 17.0 ml). By limits of agreement analysis the end-diastolic mean differences for two- and three-dimensional echocardiography were 21.1 and 12.9 ml, respectively. The limits of agreement (+/- 2 SD) were +/- 54.0 and +/- 24.8 ml, respectively. For end-systole, comparable improvement was obtained by three-dimensional echocardiography. Results for ejection fraction by the two methods were similar.nnnCONCLUSIONSnThree-dimensional echocardiography correlates highly with cineventriculography for estimation of ventricular volumes in patients and has approximately half the variability of two-dimensional echocardiography for these measurements. On the basis of this study, three-dimensional echocardiography is the preferred echocardiographic technique for measurement of ventricular volume. Three-dimensional echocardiography is equivalent to two-dimensional echocardiography for measuring ejection fraction.

Three-dimensional echocardiography: In vitro and in vivo validation of left ventricular mass and comparison with conventional echocardiographic methods

OBJECTIVESnThis study aimed to validate a method for mass computation in vitro and in vivo and to compare it with conventional methods.nnnBACKGROUNDnConventional echocardiographic methods of determining left ventricular mass are limited by assumptions of ventricular geometry and image plane positioning. To improve accuracy, we developed a three-dimensional echocardiographic method that uses nonparallel, nonintersecting short-axis planes and a polyhedral surface reconstruction algorithm for mass computation.nnnMETHODSnEleven fixed hearts were imaged by three-dimensional echocardiography, and mass was determined in vitro by multiplying the myocardial volume by the density of each heart and comparing it with the true mass. Mass at diastole and systole by three-dimensional echocardiography and magnetic resonance imaging (MRI) was compared in vivo in 15 normal subjects. Ten subjects also underwent imaging by one- and two-dimensional echocardiography, and mass was determined by Penn convention, area-length and truncated ellipsoid algorithms.nnnRESULTSnIn vitro results were r = 0.995, SEE 2.91 g, accuracy 3.47%. In vivo interobserver variability for systole and diastole was 16.7% to 27%, 14% to 18.1% and 6.3% to 12.8%, respectively, for one-, two- and three-dimensional echocardiography and was 7.5% for MRI at end-diastole. The latter two agreed closely with regard to diastolic mass (r = 0.895, SEE 11.1 g) and systolic mass (r = 0.926, SEE 9.2 g). These results were significantly better than correlations between MRI and the Penn convention (r = 0.725, SEE 25.6 g for diastole; r = 0.788, SEE 28.7 g for systole), area-length (r = 0.694, SEE 24.2 g for diastole; r = 0.717, SEE 28.2 g for systole) and truncated ellipsoid algorithms (r = 0.687, SEE 21.8 g for diastole; r = 0.710, SEE 24.5 g for systole).nnnCONCLUSIONSnImage plane positioning guidance and elimination of geometric assumptions by three-dimensional echocardiography achieve high accuracy for left ventricular mass determination in vitro. It is associated with higher correlations and lower standard errors than conventional methods in vivo.

Comparison of theoretical scattering results and ultrasonic data from clinical liver examinations

A theoretical analysis of soft-tissue ultrasonic scattering has been used to formulate specific results describing spectral parameters for tissue characterization. Results are applicable to clinical liver examinations. Three spectral parameters are mathematically expressed in terms of acoustic attenuation and the effective sizes, concentrations, and relative acoustic impedances of tissue scatters. Results from a clinical data base are shown to agree well with analytical results for each spectral parameter. Agreement is found for: spectral shapes; effects of attenuation; and correlations between parameters. Images of three spectral parameters are presented and their gray-scale features are evaluated with reference to analytical results.

Freehand three-dimensional echocardiography for determination of left ventricular volume and mass in patients with abnormal ventricles: Comparison with magnetic resonance imaging

OBJECTIVEnThe objective of this study was to validate the freehand three-dimensional echocardiographic method in patients with abnormal ventricular geometry compared with two-dimensional echocardiography using magnetic resonance imaging as a standard.nnnBACKGROUNDnTwo-dimensional echocardiographic methods for estimating left ventricular volume and mass in clinical use today are limited by inaccuracies and variations caused by use of geometric assumptions and errors in image plane positioning. Freehand three-dimensional echocardiography with operator guidance by a line of intersection display eliminates these assumptions and errors. This method of volume and mass computation has been validated as highly accurate and reproducible in healthy subjects.nnnMETHODSnLeft ventricular end-systolic and end-diastolic volumes and myocardial mass were determined by freehand three-dimensional echocardiography, by conventional two-dimensional echocardiography using the apical biplane summation of discs method (volume) and the truncated ellipsoid method (mass), by M-mode echocardiography using the Penn method (mass), and by magnetic resonance imaging in 30 patients selected only for the presence of an abnormal ventricle. Results were compared by means of linear regression and the Bland-Altman method of analysis.nnnRESULTSnThere was excellent correlation, low bias, and low variability between three-dimensional echocardiography and magnetic resonance imaging for end-diastolic volume (r = 0.90, standard error of the estimate = 31.8 ml, bias = -28.4 ml), end-systolic volume (r = 0.93, standard error of the estimate = 24.1 ml, bias = -13.1 ml), and mass (r = 0.90, standard error of the estimate = 27.3 gm, bias = -22.6 ml). Two-dimensional echocardiography was less accurate and more variable as follows: end-diastolic volume (r = 0.70, standard error of the estimate = 39.8 ml, bias = -33.5 ml), end-systolic volume (r = 0.78, standard error of the estimate = 31.2 ml, bias = -26.7 ml), and mass (r = 0.80, standard error of the estimate = 37.3 gm, bias = 28.9 ml). M-mode echocardiography mass determination (Penn method) was least accurate and most variable (r = 0.075, standard error of the estimate = 78.3 gm, bias = 78.3 gm).nnnCONCLUSIONSnFreehand three-dimensional echocardiography is a method of high accuracy and low variability for computing left ventricular volume and mass in clinical patients with abnormal ventricles. It is superior to conventional one- and two-dimensional echocardiography. The improvement achieved is attributed to elimination of geometric assumptions and image plane positioning errors and additional sampling of the ventricle.

Three-dimensional echocardiographic measurement of left ventricular volume in vitro: Comparison with two-dimensional echocardiography and cineventriculography

OBJECTIVESnThis study was designed to compare three-dimensional echocardiography, two-dimensional echocardiography and cineventriculography for the purpose of measuring left ventricular volume in vitro.nnnBACKGROUNDnThree-dimensional echocardiographic systems have been shown to be highly accurate in measuring the volumes of balloon phantoms. However, three-dimensional techniques have not been compared with standard two-dimensional echocardiography in vitro or with cineventriculography, the clinical standard for left ventricular volume measurement.nnnMETHODSnExcised porcine hearts were prepared with an internal latex sheath that could be filled and maintained with a known (true) volume of liquid. Each heart was then imaged by cineventriculography, standard two-dimensional echocardiography and three-dimensional echocardiography. Left ventricular volumes were calculated from 15 hearts at 25 volumes ranging from 50 to 280 ml by the following methods: 1) biplane cineventriculography using the area-length method; 2) two-dimensional echocardiography by the apical biplane method using a summation of discs algorithm in 15 cases and the single-plane, four-chamber method using a summation of discs algorithm in 10 cases; and 3) three-dimensional echocardiography using a polyhedral surface reconstruction volume computation algorithm based on multiple nonparallel, nonevenly spaced short-axis cross sections.nnnRESULTSnResults were compared with true volume, and a nonparametric analysis of variance was performed. Both measurement bias (systematic error) and imprecision (random error) were assessed. All methods tended to underestimate the true volume (two-dimensional echocardiography -6.1 +/- 17.6%, three-dimensional echocardiography -4.7 +/- 5.0% and biplane cineventriculography -3.9 +/- 8.2%), although differences were not significant. Although there was a significant correlation between the magnitude of measurement bias and the size of the volume being measured for two-dimensional echocardiography and cineventriculography, the bias of three-dimensional echocardiography was fairly constant over the range of volumes. When bias was accounted for, two-dimensional echocardiography was significantly less precise than cineventriculography and three-dimensional echocardiography in terms of percent error (15.3 +/- 11.9%, 5.6 +/- 5.7% and 3.9 +/- 3.4%, respectively).nnnCONCLUSIONSnThree-dimensional echocardiography using a polyhedral surface reconstruction algorithm for volume computation provides accuracy comparable to that of biplane cineventriculography in this in vitro model. Standard two-dimensional echocardiographic volume computation is significantly less accurate than the other two methods.

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.

Comparison of three-dimensional echocardiographic assessment of volume, mass, and function in children with functionally single left ventricles with two-dimensional echocardiography and magnetic resonance imaging

Diminished systolic function or inappropriate hypertrophy are considered risk factors for outcome following the Fontan procedure. These parameters are difficult to assess in univentricular hearts that do not conform to the uniform shapes prescribed by conventional 2-dimensional imaging volume algorithms. Three-dimensional echocardiography requires no geometric assumptions and has been validated in both normal and distorted left ventricles. To assess the feasibility and accuracy of this technique in patients with univentricular hearts, we compared 2- and 3-dimensional echocardiographic estimates of ventricular volume, ejection fraction, and mass in patients with functionally single left ventricles with results obtained by magnetic resonance imaging (MRI). Twelve patients with functionally single left ventricles (6 months to 22 years) underwent examination by all 3 modalities. Correlation and agreement with MRI were calculated for volumes, ejection fraction, and mass. Three-dimensional echocardiographic comparison with MRI yielded a bias of 3.4 +/- 5.5 ml and 14.2 +/- 8.3 ml for systolic and diastolic volumes, respectively. Agreement analysis for mass showed a bias of 5.8 +/- 8.4 grams. Two-dimensional echocardiography showed less agreement for both volumes and mass (bias of -2.9 +/- 8.1, 2.9 +/- 10.4 ml and -8.3 +/- 12.0 g for volume and mass, respectively, p >0.05). Ejection fraction by 3-dimensional echocardiography showed significantly closer agreement with MRI (bias of 4.4 +/- 5.3%) than 2-dimensional echocardiography (bias of 8.5 +/- 10.3%, p = 0.04). Thus, 3-dimensional echocardiography provides estimates of ventricular volumes, ejection fraction, and mass that are comparable to MRI in this select group of patients with single ventricles of left ventricular morphology.