Dynamic three-dimensional reconstruction of the left ventricle from two-dimensional echocardiograms

Acoustic characterization of a miniature matrix transducer for pediatric 3D transesophageal echocardiography

This paper presents the design, fabrication and characterization of a miniature PZT-on-CMOS matrix transducer for real-time pediatric 3-dimensional (3D) transesophageal echocardiography (TEE). This 3D TEE probe consists of a 32 × 32 array of PZT elements integrated on top of an Application Specific Integrated Circuit (ASIC). We propose a partitioned transmit/receive array architecture wherein the 8 × 8 transmitter elements, located at the centre of the array, are directly wired out and the remaining receive elements are grouped into 96 sub-arrays of 3 × 3 elements. The echoes received by these sub-groups are locally processed by micro-beamformer circuits in the ASIC that allow pre-steering up to ±37°. The PZT-on-CMOS matrix transducer has been characterized acoustically and has a centre frequency of 5.8 MHz, -6 dB bandwidth of 67%, a transmit efficiency of 6 kPa/V at 30 mm, and a receive dynamic range of 85 dB with minimum and maximum detectable pressures of 5 Pa and 84 kPa respectively. The properties are very suitable for a miniature pediatric real-time 3D TEE probe.

Automated Three-Dimensional Reconstruction of the Left Ventricle From Multiple-Axis Echocardiography

Two-dimensional echocardiography (echo) is the method of choice for noninvasive evaluation of the left ventricle (LV) function owing to its low cost, fast acquisition time, and high temporal resolution. However, it only provides the LV boundaries in discrete 2D planes, and the 3D LV geometry needs to be reconstructed from those planes to quantify LV wall motion, acceleration, and strain, or to carry out flow simulations. An automated method is developed for the reconstruction of the 3D LV endocardial surface using echo from a few standard cross sections, in contrast with the previous work that has used a series of 2D scans in a linear or rotational manner for 3D reconstruction. The concept is based on a generalized approach so that the number or type (long-axis (LA) or short-axis (SA)) of sectional data is not constrained. The location of the cross sections is optimized to minimize the difference between the reconstructed and measured cross sections, and the reconstructed LV surface is meshed in a standard format. Temporal smoothing is implemented to smooth the motion of the LV and the flow rate. This software tool can be used with existing clinical 2D echo systems to reconstruct the 3D LV geometry and motion to quantify the regional akinesis/dyskinesis, 3D strain, acceleration, and velocities, or to be used in ventricular flow simulations.

Three-dimensional adult echocardiography: where the hidden dimension helps

The introduction of three-dimensional (3D) imaging and its evolution from slow and labor-intense off-line reconstruction to real-time volumetric imaging is one of the most significant developments in ultrasound imaging of the heart of the past decade. This imaging modality currently provides valuable clinical information that empowers echocardiography with new levels of confidence in diagnosing heart disease. One major advantage of seeing the additional dimension is the improvement in the accuracy of the evaluation of cardiac chamber volumes by eliminating geometric modeling and the errors caused by foreshortened views. Another benefit of 3D imaging is the realistic views of cardiac valves capable of demonstrating numerous pathologies in a unique, noninvasive manner. This article reviews the major technological developments in 3D echocardiography and some of the recent literature that has provided the scientific basis for its clinical use.

Head to head comparison of 2D vs real time 3D dipyridamole stress echocardiography

Real-time three-dimensional (RT-3D) echocardiography has entered the clinical practice but true incremental value over standard two-dimensional echocardiography (2D) remains uncertain when applied to stress echo. The aim of the present study is to establish the additional value of RT-3D stress echo over standard 2D stress echocardiography. We evaluated 23 consecutive patients (age = 65 ± 10 years, 16 men) referred for dipyridamole stress echocardiography with Sonos 7500 (Philips Medical Systems, Palo, Alto, CA) equipped with a phased – array 1.6–2.5 MHz probe with second harmonic capability for 2D imaging and a 2–4 MHz matrix-phased array transducer producing 60 × 70 volumetric pyramidal data containing the entire left ventricle for RT-3D imaging. In all patients, images were digitally stored in 2D and 3D for baseline and peak stress with a delay between acquisitions of less than 60 seconds. Wall motion analysis was interpreted on-line for 2D and off-line for RT-3D by joint reading of two expert stress ecocardiographist. Segmental image quality was scored from 1 = excellent to 5 = uninterpretable. Interpretable images were obtained in all patients. Acquisition time for 2D images was 67 ± 21 sec vs 40 ± 22 sec for RT-3D (p = 0.5). Wall motion analysis time was 2.8 ± 0.5 min for 2D and 13 ± 7 min for 3D (p = 0.0001). Segmental image quality score was 1.4 ± 0.5 for 2D and 2.6 ± 0.7 for 3D (p = 0.0001). Positive test results was found in 5/23 patients. 2D and RT-3D were in agreement in 3 out of these 5 positive exams. Overall stress result (positive vs negative) concordance was 91% (Kappa = 0.80) between 2D and RT-3D. During dipyridamole stress echocardiography RT-3D imaging is highly feasible and shows a high concordance rate with standard 2D stress echo. 2D images take longer time to acquire and RT-3D is more time-consuming to analyze. At present, there is no clear clinical advantage justifying routine RT-3D stress echocardiography use.

Three-Dimensional Echocardiographic Evaluation of the Heart Chambers: Size, Function, and Mass

The major advantage of three-dimensional (3D) ultrasound imaging of the heart is the improvement in the accuracy of the echocardiographic evaluation of cardiac chamber volumes, which is achieved by eliminating the need for geometric modeling and the errors caused by foreshortened 2D views. In this article, we review the literature that has provided the scientific basis for the clinical use of 3D ultrasound imaging of the heart in the assessment of cardiac chamber size, function, and mass, and discuss its potential future applications.

Real-time three-dimensional echocardiography: technological gadget or clinical tool?

The complex anatomy of cardiac structures requires three-dimensional spatial orientation of images for a better understanding of structure and function, thereby improving image interpretation. Real-time three-dimensional echocardiography is a recently developed technique based on the design of an ultrasound transducer with a matrix array that rapidly acquires image data in a pyramidal volume. The simultaneous display of multiple tomographic images allows three-dimensional perspective and the anatomically correct examination of any structure within the volumetric image. As a consequence, it is less operator-dependent and hence more reproducible. Dedicated software systems and technologies are based on high-performance computers designed for graphic handling of three-dimensional images by providing possibilities beyond those obtainable with echocardiography. This methodology allows simultaneous display of multiple superimposed planes in an interactive manner as well as a quantitative assessment of cardiac volumes and ventricular mass in a three-dimensional format without a pre-established assumption of cardiac chamber geometry. In addition, myocardial contraction and/or perfusion abnormalities are clearly identified. Finally, real-time three-dimensional colour Doppler flow mapping enables complete visualisation of the regurgitant jet and new ways of assessing regurgitant lesion severity. Thus, this technique expands the abilities of non-invasive cardiology and may open new doors for the evaluation of cardiac diseases. In this article, current and future clinical applications of real-time three-dimensional echocardiography are reviewed.

Three-Dimensional Echocardiography

Over the past 3 decades, echocardiography has become a major diagnostic tool in the arsenal of clinical cardiology for real-time imaging of cardiac dynamics. More and more, cardiologists' decisions are based on images created from ultrasound wave reflections. From the time ultrasound imaging technology provided the first insight into the human heart, our diagnostic capabilities have increased exponentially as a result of our growing knowledge and developing technology. One of the most significant developments of the last decades was the introduction of 3-dimensional (3D) imaging and its evolution from slow and labor-intense off-line reconstruction to real-time volumetric imaging. While continuing its meteoric rise instigated by constant technological refinements and continuing increase in computing power, this tool is guaranteed to be integrated in routine clinical practice. The major proven advantage of this technique is the improvement in the accuracy of the echocardiographic evaluation of cardiac chamber volumes, which is achieved by eliminating the need for geometric modeling and the errors caused by foreshortened views. Another benefit of 3D imaging is the realistic and unique comprehensive views of cardiac valves and congenital abnormalities. In addition, 3D imaging is extremely useful in the intraoperative and postoperative settings because it allows immediate feedback on the effectiveness of surgical interventions. In this article, we review the published reports that have provided the scientific basis for the clinical use of 3D ultrasound imaging of the heart and discuss its potential future applications.

Live 3D Echocardiography: A Replacement for Traditional 2D Echocardiography?

OBJECTIVE

We describe the development of real-time 3D imaging and review the previously used versions of 3D echocardiography so that the reader will appreciate why current developments truly do represent a quantum leap in the technology.

CONCLUSION

Three-dimensional echocardiography has now been shown to have several advantages over 2D echocardiography, particularly for volume measurements, visualization of septal defects, and whole-valve evaluation. Given these data, it is clear that 3D echocardiography is here to stay and soon will become part of routine echocardiographic examinations.

Impact of three-dimensional echocardiography in valvular heart disease

PURPOSE OF REVIEW

Recent advances in the field of three-dimensional (3D) echocardiography have allowed improved visualization of cardiac structures. These advances have also provided valuable insights into cardiac function. The purpose of this review is to describe the recent developments in 3D echocardiography in assessing valvular heart disease.

RECENT FINDINGS

Application of 3D echocardiography to valvular heart disease has improved with advances made in both the hardware and software components of 3D ultrasound systems. The most significant advancement has been the development of a matrix transducer that is capable of rapid real-time 3D acquisition and rendering. There have been many studies evaluating 3D echocardiographic assessment of mitral valve disease, aortic valve disease, as well as congenital heart disease using both real-time 3D transthoracic echocardiography (TTE) as well as off-line reconstructed 3D images from transesophageal echocardiography (TEE) using post image processing. More recent studies have combined the structural 3D information with color Doppler 3D imaging, providing qualitative functional information.

SUMMARY

Developments in the field of 3D ultrasound imaging have allowed better qualitative assessment of valvular structures. The addition of color flow Doppler to the 3D imaging has provided improved visualization of regurgitant lesions and holds great promise for improved quantitative assessment of such lesions. The ongoing miniaturization of transducers and improvements in hardware and software components of ultrasound systems will certainly enhance both the ease of image acquisition as well as image quality, which should result in more precise quantitation of valvular dysfunction. However, clinical benefits of 3D echocardiography are yet to be demonstrated in properly conducted clinical trials, which are needed for wider acceptance of this technique.

Real-Time Three-Dimensional Echocardiography Using a Novel Matrix Array Transducer

Three-dimensional echocardiography has multiple advantages over two-dimensional echocardiography, such as accurate left ventricular quantification and improved spatial relationships. However, clinical use of three-dimensional echocardiography has been impeded by tedious and time-consuming methods for data acquisition and post-processing. A newly developed matrix array probe, which allows real-time three-dimensional imaging with instantaneous on-line volume-rendered reconstruction, direct manipulation of thresholding, and cut planes on the ultrasound unit may overcome the aforementioned limitations. This report will review current methods of three-dimensional data acquisition, emphasizing the real-time methods and clinical applications of the new matrix array probe.

Real-time three-dimensional ultrasound methods for shape analysis and visualization

Real-time three-dimensional (RT3D) ultrasound is a relatively new imaging modality that uses a special ultrasound transducer consisting of a matrix array of elements. The array electronically steers an ultrasound beam to interrogate a 3D volume of tissue. The real-time nature of RT3D ultrasound differentiates it from reconstructed 3D ultrasound, in which a conventional ultrasound transducer is moved mechanically through the third dimension. RT3D ultrasound is considerably faster than reconstructed 3D ultrasound, making it suitable for capturing continuous rapid motion such as that of the beating heart. Although RT3D ultrasound has not yet found widespread clinical use, these scanners are presently employed in more than 20 locations worldwide, primarily for cardiac research. The author helped develop the RT3D ultrasound technology as well as specialized analysis and visualization methods for the resulting data. In developing such methods, it has been necessary to consider the physical and mathematical processes by which the ultrasound data are collected. Difficulties arise because of high noise, variation in contrast and intensity between scans, ultrasound's nonrectilinear coordinate system, and the anisotropic nature of the echoes themselves. This article reviews these specific difficulties and provides solutions that are applicable to generalized analysis and visualization of RT3D ultrasound data. Some of the methods presented can also be applied to other imaging modalities with nonrectilinear coordinates.

Positional localization: three-dimensional transthoracic echocardiographic techniques for the measurement of cardiac mass, volume, and function

An accurate and reproducible determination of cardiac volume and mass is important for the selection and timing of therapeutic interventions. Quantitative three-dimensional echocardiography has evolved to provide these measurements with the use of a noninvasive, readily available, and inexpensive technique. We introduce and review the principle of positional localization as well as the clinical application of this technique for the measurement of cardiac volume and mass.

Three-dimensional echocardiography paves the way toward virtual reality

The heart is a three-dimensional (3-D) object and, with the help of 3-D echocardiography (3-DE), it can be shown in a realistic fashion. This capability decreases variability in the interpretation of complex pathology among investigators. Therefore, it is likely that the method will become the standard echocardiography examination in the future. The availability of volumetric data sets allows retrieval of an infinite number of cardiac cross-sections. This results in more accurate and reproducible measurements of valve areas, cardiac mass and cavity volumes by obviating geometric assumptions. Typical 3-DE parameters, such as ejection fraction, flow jets, myocardial perfusion and LV wall curvature, may become important diagnostic parameters based on 3-DE. However, the freedom of an infinite number of cross-sections of the heart can result in an often-encountered problem of being "lost in space" when an observer works on a 3-DE image data set. Virtual reality computing techniques in the form of a virtual heart model can be useful by providing spatial "cardiac" information. With the recent introduction of relatively low cost portable echo devices, it is envisaged that use of diagnostic ultrasound (US) will be further boosted. This, in turn, will require further teaching facilities. Coupling of a cardiac model with true 3-D echo data in a virtual reality setting may be the answer.

Measurements of organ volume by ultrasonography

In a clinical context, measurements of organ volume are often performed in the diagnosis and follow-up of patients with a variety of diseases. Ultrasonography is a cheap, widely available and non-hazardous imaging modality to use for estimation of volumes, and a range of two- and three-dimensional methods have emerged to accomplish this task. This paper reviews some of the ultrasound methods available in cardiology, gastroenterology, nephrology/urology and gynaecology/obstetrics. Using two-dimensional (2D) ultrasound, the simplest method of calculating the volume of an organ is based on the multiplication of three diameters perpendicular to each other. These 2D methods are often based on geometrical assumptions which may introduce significant errors in volume estimation. Therefore, volume estimation based on three-dimensional (3D) ultrasound has been developed to increase accuracy and precision. At present, the process of making 3D images based on ultrasonography is divided into five steps: data acquisition, data digitization, data storage, data processing and data display. In conclusion, ultrasonography is a useful and reliable tool to calculate volumes of organs. In particular, 3D ultrasonography seems promising in this respect and appears to be superior to 2D ultrasonography in accuracy and precision in volume measurements.

Assessment of regional wall motion abnormalities with real-time 3-dimensional echocardiography

Accurate characterization of regional wall motion abnormalities requires a thorough evaluation of the entire left ventricle (LV). Although 2-dimensional echocardiography is frequently used for this purpose, the inability of tomographic techniques to record the complete endocardial surface is a limitation. Three-dimensional echocardiography, with real-time volumetric imaging, has the potential to overcome this limitation by capturing the entire volume of the LV and displaying it in a cineloop mode. The purpose of this study was to assess the feasibility of using real-time 3-dimensional (RT3D) echocardiography to detect regional wall motion abnormalities in patients with abnormal LV function and to develop a scheme for the systematic evaluation of wall motion by using the 3-dimensional data set. Twenty-six patients with high-quality 2-dimensional echo images and at least 1 regional wall motion abnormality were examined with RT3D echocardiography. For 2-dimensional echocardiography, wall motion was analyzed with a 16-segment model and graded on a 4-point scale from normal (1) to dyskinetic (4), from which a wall motion score index was calculated. Individual segments were then grouped into regions (anterior, inferoposterior, lateral, and apical) and the number of regional wall motion abnormalities was determined. The RT3D echocardiogram was recorded as a volumetric, pyramid-shaped data set that contained the entire LV. Digital images, consisting of a single cardiac cycle cineloop, were analyzed off-line with a computerized display of the apical projection. Two intersecting orthogonal apical projections were simultaneously displayed in cineloop mode, each independently tilted to optimize orientation and endocardial definition. The 2 planes were then slowly rotated about the major axis to visualize the entire LV endocardium. Wall motion was then graded in 6 equally spaced views, separated by 30 degrees, yielding 36 segments per patient. A higher percentage of segments were visualized with 2-dimensional versus RT3D echocardiography (97% vs 83%, respectively, P <.001). With the use of the 2-dimensional echocardiographic results as the standard, RT3D echocardiography detected 55 (96%) of 57 regional wall motion abnormalities. Analysis of the RT3D echocardiograms resulted in 3 false-negative and 5 false-positive findings. The total number of regional wall motion abnormalities was correctly classified by RT3D echocardiography in 19 (73%) of 26 patients. RT3D echocardiography detected 11 of 13 anterior, 19 of 20 inferoposterior, 9 of 9 lateral, and 15 of 15 apical wall motion abnormalities. An excellent correlation was found between the 2 techniques for assessment of the regional wall motion score index (r = 0.89, P <.001). This initial clinical study demonstrates the feasibility and potential advantages of RT3D echocardiography for the assessment of regional LV function. Compared with 2-dimensional echocardiography, this new method permits recording of the entire LV in a single beat, allowing the extent and location of the regional wall motion abnormalities to be determined.

A simplified, practical echocardiographic approach for 3-dimensional surfacing and quantitation of the left ventricle: clinical application in patients with abnormally shaped hearts

The goal of this study was to validate the quantitative accuracy of a system for 3-dimensional (3D) echocardiographic reconstruction of the left ventricle to assess its volume and function in human beings by using 3 apical views as a simplified technique to promote practical clinical application. End-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (EF) were obtained by 3D echocardiography in 50 patients with dilated or geometrically distorted left ventricles and compared with values from magnetic resonance imaging (20 consecutive patients), angiography (22 consecutive patients), and radionuclide imaging (8 consecutive patients). Three-dimensional results were also compared with 2-dimensional (2D) echocardiographic estimates. Three-dimensional left ventricular reconstruction provided values that correlated and agreed well with pooled data from the other techniques for EDV (y = 0.93x + 9.1, r = 0.95, standard error of the estimate [SEE] = 15.2 mL, mean difference = -0.5 +/- 15.4 mL), ESV (y = 0.94x + 4.3, r = 0. 96, SEE = 11.4 mL, mean difference = 0.4 +/- 11.5 mL), and EF (y = 0. 90x + 4.1, r = 0.92, SEE = 6.2%, mean difference = -0.9 +/- 6.4%) (all mean differences not significant versus 0), with greater errors by 2D echocardiography. Intraobserver and interobserver variabilities of 3D echocardiography were less than 6% for EDV, ESV, and EF. The overall time for image acquisition and 3D reconstruction was 5 to 8 minutes. Although this 3D method uses only a small number of apical views, it accurately calculates EDV, ESV, and EF in patients with dilated and asymmetric left ventricles and is more accurate than 2D echocardiography. The flexible surface fit used to combine the 3 views provides a convenient visual output as well as quantitation. This simple and rapid 3D method has the potential to facilitate routine clinical applications that assess left ventricular function and changes that occur with remodeling.

Three-Dimensional Echocardiography: Precision and Accuracy of Left Ventricular Volume Measurement Using Rotational Geometry with Variable Numbers of Slice Resolution

We developed a new, rapid (6 seconds) acquisition technique allowing collection of approximately six through nine apical rotational tomograms for three-dimensional (3-D) echocardiography. To justify an appropriate sampling density for precise and accurate measurement of chamber volumes in left ventricles with complicated shape, we designed a validation study in vitro using six canine heart specimens with irregular, asymmetric left ventricles with known volumes (28.5 to 104.3 ml; mean, 71.2 ml). The number of equally spaced slices were incrementally deleted from the original high resolution scans (48 slices) to 2 slices in 3-D reconstruction. We created subgroups of 48- and 36-, 24- and 16-, 12- and 8-, 6- and 4-, and 3- and 2-component slices to compare left ventricular (LV) volumes measured in 3-D images with different slice resolution with the reference standard measured in the specimen. The accuracy and precision of LV volume were relatively constant in the subgroup of 4- and 6- through 36- and 48-component slices. When the subgroup with 6- and 4-component slices was used, the correlation was r = 0.991, P < 0.0001, root-mean-square percent error of 5.0%, bias of 0.5 +/- 3.7 ml, and interobserver variability of 5.0%. With the reduction in component slices equal or less than three, the accuracy decreased significantly (root-mean-square percent error = 8.1% and bias = -2.0 +/- 5.7 ml) compared with higher slice resolutions. This study demonstrated that 3-D echocardiography using apical rotational techniques can accurately quantify LV volume in the canine heart specimens with irregular shapes with as few as 4-6 axial slices. The rapid 3-D acquisition technique is therefore anticipated to yield precise and accurate LV volumetry.

Three-dimensional echocardiographic reconstruction: description and applications of a simplified technique for quantitative assessment of left ventricular size and function

A simplified system for three-dimensional (3D) reconstruction of the left ventricle and quantitation of its size and function is described. This system requires the acquisition of a minimum number of two-dimensional (2D) echocardiographic apical views, which are obtained by rotation of the probe about the initial imaging point. Traced endocardial borders are spatially reconstructed according to the common apex and longitudinal axis of the views and to the measured or assumed angular relation between scanned planes. This technique has been applied in vitro to regular and irregular ventricular phantoms, yielding excellent accuracy for volume calculation. Also, it has been applied clinically for left ventricular volume, stroke volume, and ejection fraction calculation in both normal subjects and patients with various cardiac diseases, providing good results compared with other independent imaging techniques and showing increased accuracy with respect to 2D echocardiographic methods. Because this is obtained without substantial increase in time, effort, or cost, this simplified technique for 3D reconstruction should therefore be of value in daily clinical echocardiographic practice.

Three-dimensional electrophysiological imaging of the intact canine left ventricle using a noncontact multielectrode cavitary probe: study of sinus, paced, and spontaneous premature beats

BACKGROUND

The feasibility of measuring cavitary electrograms using a noncontact probe and reconstructing endocardial surface electrograms and activation sequences during paced beats was previously demonstrated in the isolated canine left ventricle (LV). The objective of the present study was to develop and test a high-resolution, three-dimensional, endocardial electrophysiological imaging technique that simultaneously reconstructs endocardial surface electrograms and their corresponding activation sequences during normal and abnormal beats with the use of cavitary electrograms measured with a noncontact multielectrode probe in the intact canine LV.

METHODS AND RESULTS

A 128-electrode probe was inserted into the intact canine LV. Probe unipolar electrograms were simultaneously acquired during sinus, artificially paced, and spontaneous premature beats. Representative endocardial electrograms were measured directly using eight needle electrodes (the "gold standard"). A probe-cavity realistic, three-dimensional geometric model was constructed using two-dimensional epicardial echocardiography. Boundary element methods and numeric regularization were used to compute electrograms at 194 sites on the endocardium. In eight pacing protocols, computed endocardial electrograms correlated well with directly measured electrograms (r=.88). Corresponding activation times were also in agreement with those determined from measured endocardial electrograms (activation error, 4.7 ms). The earliest region of activation was invariably in the vicinity of the pacing needle (spatial error, 9.2 mm). Subsequently, the site of origin of ischemia-induced spontaneous ventricular premature beats and the ensuing sequence of depolarization was identified.

CONCLUSIONS

Noncontact mapping provides realistic, three-dimensional electrophysiological images of the endocardium, on a beat-by-beat basis, that localize the sites of origin of premature beats and reconstruct their activation sequences.

Tomographic three-dimensional echocardiographic determination of chamber size and systolic function in patients with left ventricular aneurysm: comparison to magnetic resonance imaging, cineventriculography, and two-dimensional echocardiography

BACKGROUND

Two-dimensional (2D) echocardiographic approaches based on geometric assumptions face the greatest limitations and inaccuracies in patients with left ventricular (LV) aneurysms. Three-dimensional (3D) echocardiographic techniques can potentially overcome these limitations; to date, however, although tested in experimental models of aneurysms, they have not been applied to a series of patients with such distortion. The purpose of this study was therefore to validate the clinical application of tomographic 3D echocardiography (3DE) by the routine transthoracic approach to determine LV chamber size and systolic function without geometric assumptions in patients with LV aneurysms.

METHODS AND RESULTS

In 23 patients with chronic stable LV aneurysms, LV end-systolic and end-diastolic volumes (LVEDV, LVESV) and ejection fraction (LVEF) by tomographic 3DE were compared with results from 3D magnetic resonance tomography (3DMRT) as an independent reference as well as with the conventional techniques of single plane and biplane 2D echocardiography and biplane cineventriculography. Dynamic 3DE image data sets were obtained from a transthoracic apical view with the use of a rotating probe with acquisition gated to control for ECG and respiration (Echoscan, TomTec). Volumes were calculated from the 3D data sets by summating the volumes of multiple parallel disks. 3DE results correlated and agreed well with those by 3DMRT, with better correlation and agreement than provided by other techniques for LVEDV (3DE: r=.97, SEE=14.7 mL, SD of differences from 3DMRT=14.5 mL; other techniques: r=.84 to .93, SEE=30.7 to 41.6 mL [P<.001 versus 3DE by F test], SD of differences=31.5 to 40.7 mL [P<.001 versus 3DE by F test]). The same also pertained to LVESV (3DE: r=.97, SEE=12.4 mL, SD of differences=12.9 mL; other techniques: r=.81 to .90, SEE=24.7 to 37.2 mL [P<.001], SD of differences=27.6 to 36.8 mL [P<.005]) and LVEF (3DE: r=.74, SEE=5.6%, SD of differences=6.7%; other techniques: r=.14 to .59, SEE=9.5% to 10.1% [P<.01], SD of differences=9.5% to 12.6% [P<.05]). Compared with 3DMRT, 3DE was less time consuming and patient discomfort was less.

CONCLUSIONS

Tomographic 3DE is an accurate noninvasive technique for calculating LV volumes and systolic function in patients with LV aneurysm. Unlike current 2D methods, tomographic 3DE requires no geometric assumptions that limit accuracy.

Reference Techniques for Left Ventricular Volume Measurement by Three-Dimensional Echocardiography: Determination of Precision, Accuracy, and Feasibility

The use of multiple in vitro reference methods to validate three-dimensional (3-D) echocardiographic techniques makes comparison difficult. In an attempt to establish a reference standard, we studied precision, accuracy, and feasibility of a true left ventricular (LV) volume measurement in six dog heart specimens using three techniques, called fluid, sheath, and cast. LV volumes ranged from 30 to 105 mL. Intraobserver variability was minimal in all combinations (1.26% to 2.8%) with a statistically insignificant tendency to higher values in the cast method. The cast method, however, exhibited significantly higher interobserver variability (5.78%) as compared to that ranging from 1.47% to 1.59% in the remaining two techniques. Regression analysis demonstrated high correlations among the three techniques assessed by 95% confidence limits and correlation coefficient (R(2) > 0.98, P < 0.01). Mean differences among the techniques (0.12 to 1.08 mL) were not significant. The fluid technique was easy to perform. The sheath technique required some practice. The cast method was sensitive to accurate preparation of a gelatin mixture. We conclude that the fluid and sheath techniques are precise, accurate, and feasible. We recommend their use as reference standards in laboratory LV volume measurement. Validation 3-D echocardiographic studies using either of these two techniques will be comparable. Although the accuracy of the cast technique is excellent, its lower precision makes it a second choice. It could be used in cases where an LV cavity cast is required and higher interobserver variability is acceptable.

Quantitative three dimensional echocardiography in patients with pulmonary hypertension and compressed left ventricles: comparison with cross sectional echocardiography and magnetic resonance imaging

OBJECTIVE

To evaluate the accuracy of quantitative three dimensional echocardiography in patients with deformed left ventricles.

DESIGN

Three dimensional and cross sectional echocardiographic estimates of left ventricular volume and ejection fraction were prospectively compared to those obtained from magnetic resonance imaging.

SETTING

Echocardiography laboratory of a university hospital.

PATIENTS

26 patients (9 months to 42 years, median age 11 years) with pulmonary hypertension and fixed reversal of normal interventricular septal curvature.

MAIN OUTCOME MEASURES

Left ventricular end diastolic and end systolic volumes and ejection fraction.

RESULTS

Three dimensional echocardiographic comparison to magnetic resonance imaging (MRI) yielded r values of 0.94 and 0.87 with a bias of -6.9 (SD 6.9) ml and -16 (11.2) ml for systolic and diastolic volumes respectively. Inter-observer variability was minimal (8.3% and 7.6% respectively). Cross sectional echocardiography gave correlation coefficients of 0.62 and 0.80 and bias of 3.1 (14.1) ml and 16.3 (18.3) ml for systolic and diastolic volumes respectively. Ejection fraction by three dimensional echocardiography also had closer agreement with MRI (bias = 1.1 (7.7)%) than cross sectional echocardiography (bias = 4.4 (13.9)%).

CONCLUSIONS

Three dimensional echocardiography provides reliable estimates of left ventricular volumes and ejection fraction, comparable to magnetic resonance imaging in pulmonary hypertension patients with compressed ventricular geometry. Because it eliminates the need for geometric assumptions it shows closer agreement with magnetic resonance imaging in that setting than cross sectional echocardiography.

Four-dimensional echocardiography: methods and clinical application

4DE (i.e., dynamic three-dimensional) echocardiography is a new developing technique in recent years. In our study, a three-dimensional echo scan computer system was used to acquire and store the two-dimensional information, then to reconstruct the stereoscopic image of the heart according to its space-time continuum. It can yield a better approach, which can help identify the various structures of the heart and great arteries and facilitate understanding of spatial relations and motion. In addition, it can display physiologic information such as the direction, course, size, and shape of the blood flow. We have examined 138 patients by both transthoracic and transesophageal approaches. Our preliminary experience shows that 4DE is of great value in diagnosing congenital heart disease and valvular disease.

Insights from three-dimensional echocardiographic laser stereolithography. Effect of leaflet funnel geometry on the coefficient of orifice contraction, pressure loss, and the Gorlin formula in mitral stenosis

BACKGROUND

Three-dimensional echocardiography can allow us to address uniquely three-dimensional scientific questions, for example, the hypothesis that the impact of a stenotic valve depends not only on its limiting orifice area but also on its three-dimensional geometry proximal to the orifice. This can affect the coefficient of orifice contraction (Cc = effective/anatomic area), which is important because for a given flow rate and anatomic area, a lower Cc gives a higher velocity and pressure gradient, and Cc, routinely assumed constant in the Gorlin equation, may vary with valve shape (60% for a flat plate, 100% for a tube). To date, it has not been possible to study this with actual valve shapes in patients.

METHODS AND RESULTS

Three-dimensional echocardiography reconstructed valve geometries typical of the spectrum in patients with mitral stenosis: mobile doming, intermediate conical, and relatively flat immobile valves. Each geometry was constructed with orifice areas of 0.5, 1.0 and 1.5 cm2 by stereolithography (computerized laser polymerization) (total, nine valves) and studied at physiological flow rates. Cc varied prominently with shape and was larger for the longer, tapered dome (more gradual flow convergence proximal and distal to the limiting orifice): for an anatomic orifice of 1.5 cm2, Cc increased from 0.73 (flat) to 0.87 (dome), and for an area of 0.5 cm2, from 0.62 to 0.75. For each shape, Cc increased with increasing orifice size relative to the proximal funnel (more tubelike). These variations translated into important differences of up to 40% in pressure gradient for the same anatomic area and flow rate (greatest for the flattest valves), with a corresponding variation in calculated Gorlin area (an effective area) relative to anatomic values.

CONCLUSIONS

The coefficient of contraction and the related net pressure loss are importantly affected by the variations in leaflet geometry seen in patients with mitral stenosis. Three-dimensional echocardiography and stereolithography, with the use of actual information from patients, can address such uniquely three-dimensional questions to provide insight into the relations between cardiac structure, pressure, and flows.

Validation of three-dimensional echocardiography for quantifying the extent of dyssynergy in canine acute myocardial infarction: comparison with two-dimensional echocardiography

OBJECTIVES

This study was designed to compare the accuracy of three- and two-dimensional echocardiography for quantifying the extent of abnormal wall motion in experimental acute myocardial infarction, as correlated with the pathologic determination of infarct size.

BACKGROUND

Two-dimensional echocardiographic estimations of the fraction of myocardium showing abnormal wall motion are often used as an index of infarct size even though they rely on image plane positioning and geometric assumptions that may not be valid. Three-dimensional echocardiographic reconstruction of the endocardial surface eliminates the need for these assumptions and may improve echocardiographic estimates of infarct size.

METHODS

Coronary ligation was performed in 14 open chest dogs, and echocardiographic imaging of the ventricle was performed 6 h later. Three-dimensional echocardiography used seven or eight spatially registered short-axis images to measure percent of endocardial surface and mass showing abnormal wall motion. Three two-dimensional echocardiographic methods using multiple, nonpatially registered images were evaluated. One method used seven or eight-axis slices and a summation of discs algorithm for computing surface area. The second method used the same images and a conical model for the left ventricle. The third used basal, middle and apical short-axis plus apical four- and two-chamber views comparing summed endocardial lengths showing abnormal wall motion with the total of the endocardial dimensions, expressed as percent. The percent of left ventricular mass and surface area infarcted was determined by staining with triphenyltetrazolium chloride.

RESULTS

Three-dimensional echocardiographic measurements of endocardial surface and correlated more closely with infarct mass (r = 0.94, SEE +/- 3.6%) than did the two-dimensional method using the summation of discs algorithm (r = 0.85, SEE +/- 6.6%), he summation of conical sections algorithm (r = 0.82, SEE +/- 5.4%) or the method using summed endocardial lengths (r = 0.79, SEE +/- 7.4%). Limits of agreement analysis comparing mass showing abnormal wall motion with anatomic infarct mass surface area showing abnormal wall motion with anatomic infarct surface area showed the smallest limits for three-dimensional echocardiography.

CONCLUSIONS

Three-dimensional echocardiography is a more accurate means of noninvasively estimating myocardial infarct size in this canine model than two-dimensional echocardiography.

A systematic approach to echocardiographic image acquisition and three-dimensional reconstruction with a subxiphoid rotational scan

Rotational scanning from the subxiphoid position is an image acquisition technique used for reconstruction of dynamic three-dimensional echocardiographic images in infants and small children. The orientation of the heart within the three-dimensional data set is variable and dependent on the image plane at which rotational scanning was initiated. We describe an image acquisition technique that standardizes the orientation of the heart within the three-dimensional data set, thereby permitting a systematic approach to the reconstruction of three-dimensional renderings. Thirteen infants and small children with congenital heart disease were studied by this approach. Illustrative examples are provided. The average time required to derive a three-dimensional rendering was 37 +/- 9 minutes. We conclude that subxiphoid rotational scanning by a systematic approach to image acquisition and reconstruction can be applied successfully to the derivation of three-dimensional renderings of congenital cardiac defects.

Quantitative three-dimensional reconstruction of left ventricular volume with complete borders detected by acoustic quantification underestimates volume

Recently a new acoustic-quantification (AQ) technique has been developed to provide on-line automated border detection with an integrated backscatter analysis. Prior studies have largely correlated AQ areas with volumes without direct comparison of volumes for agreement. By using complete AQ-detected borders as the input to a validated method for three-dimensional echocardiographic (3DE) reconstruction, we can compare an entire cavity volume measured with the aid of AQ against a directly measured volume. This would also explore the possibility of applying AQ to 3DE reconstruction to reduce tracing time and enhance routine applicability. To compare reconstructed volumes with actual values in a stable standard allowing direct volume measurement, the left ventricles of 13 excised animal hearts were studied with a 3DE system that automatically combines two-dimensional (2D) images and their locations. Intersecting 2D views were obtained with conventional scanning and AQ imaging, with gains optimized to permit 3D reconstruction by detecting the most continuous AQ borders for each view, with maximal cavity size. Reconstruction was performed with manually traced central endocardial reflections and AQ-detected borders visually reproduced the left ventricular shapes; the AQ reconstructions, however, were consistently smaller. The reconstructed left ventricular (LV) volumes correlated well with actual values by both manual and AQ techniques (r = 0.93 and 0.88, with standard errors of 2.3 cc and 2.0 cc, p = not significant [NS]). Agreement with actual values was relatively close for the manually traced borders (y = 0.93x + 0.68, mean difference = -0.8 +/-2.2 cc). AQ-derived reconstructions consistently underestimated LV volume by 39 +/- 10% (y = 0.62x-0.09, mean difference = -7.8 +/- 3.0 cc, different from manually traced and actual volumes by analysis of variance [ANOVA], F = 69, p<0.00001). The AQ-detected threshold signal was displaced into the cavity, and volume between walls and false tendons was excluded, leading to underestimation, which increased with increasing cavity volume (r = 0.76). The AQ technique can therefore be applied to 3DE reconstruction, providing volumes that correlate well with directly measured values in a stable in vitro standard, minimizing observer decisions regarding manual border placement after image acquisition. However, when the complete borders needed for 3D reconstruction are used, absolute volumes are underestimated with current algorithms that integrate backscatter and displace the detected threshold into the ventricular cavity.

Volume estimation from multiplanar 2D ultrasound images using a remote electromagnetic position and orientation sensor

A system is described for calculating volume from a sequence of multiplanar 2D ultrasound images. Ultrasound images are captured using a video digitising card (Hauppauge Win/TV card) installed in a personal computer, and regions of interest transformed into 3D space using position and orientation data obtained from an electromagnetic device (Polhemus, Fastrak). The accuracy of the system was assessed by scanning 10 water filled balloons (13-141 mL), 10 kidneys (147-200 mL) and 16 fetal livers (8-37 mL) in water using an Acuson 128XP/10 (5 MHz curvilinear probe). Volume was calculated using the ellipsoid, planimetry, tetrahedral and ray tracing methods and compared with the actual volume measured by weighing (balloons) and water displacement (kidneys and livers). The mean percentage error for the ray tracing method was 0.9 +/- 2.4%, 2.7 +/- 2.3%, 6.6 +/- 5.4% for balloons, kidneys and livers, respectively. So far the system has been used clinically to scan fetal livers and lungs, neonate brain ventricles and adult prostate glands.

Dynamic three-dimensional transesophageal echocardiography using a computed tomographic imaging probe--clinical potential and limitation

Dynamic three-dimensional echocardiography is a new diagnostic tool for spatial visualisation of cardiac anatomy and volumetric assessment. A computer-controlled probe acquires parallel tomographic slices, from which dynamic three-dimensional images of the heart can be reconstructed. Thirty adult patients with valvular heart diseases, congenital heart diseases, intracardiac masses, heart failure and other cardiac lesions, underwent conventional two-dimensional (n = 30), three-dimensional echocardiography (n = 30) and thermodilution (n = 17). The feasibility, usefulness and possibility of simulating a surgical view of intracardiac anatomy and exact volumetry were determined. The two different morphologic images were compared qualitatively. For quantitative analysis volumetry was performed using standard thermodilution technique and dynamic three-dimensional echocardiography. In more than 80% of the patients additional morphologic information was gained and a strong correlation (r = 0.75-0.95) between two volumetry assessments was found. Based on this findings, dynamic three-dimensional echocardiography is an additional and valuable approach in the perioperative and intensive care management in this group of patients.

Three-dimensional flow images by reconstruction from two-dimensional vector velocity maps

A method for constructing three-dimensional images of flow is described. The technique involves the acquisition of numerous closely spaced planes, each comprised of a map of the two-dimensional velocities measured in that plane. Each such vector velocity map is formed by tracking the motion of small regions of ultrasonic speckle between two ultrasonic acquisitions separated by a short time interval. In contrast to current Doppler velocity methods, this technique measures both the axial and lateral components of flow and is not subject to aliasing. The resulting series of two-dimensional vector velocity maps is then combined into a three-dimensional data set, which can be manipulated with appropriate software to yield quantitative three-dimensional displays of the flow within the interrogated volume. In this article we present such images obtained from measurements of in vitro laminar flow in a vessel, as well as a free jet phantom. The results allow comprehensive visualization of the three-dimensional flow characteristics, indicating promise for more complete and quantitative clinical assessment of blood flow.

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

BACKGROUND

Reliable, 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.

METHODS AND RESULTS

Fifty-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%).

CONCLUSIONS

Determination 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.

Three-dimensional echocardiography: new views from old windows

Images

Three dimensional reconstruction of the heart with rotational acquisition: methods and clinical applications

Images

Quantitative three-dimensional reconstruction of aneurysmal left ventricles. In vitro and in vivo validation

BACKGROUND

Current two-dimensional (2D) echocardiographic measures of left ventricular (LV) volume are most limited by aneurysmal distortion, which restricts application of simple geometric models that assume symmetrical shape. 2D methods also fail to provide separate volumes of the aneurysm and nonaneurysmal residual LV cavity, which could help assess the stroke volume wasted by dyskinesis and the potential residual LV body to guide surgical approaches and predict their outcome. Three-dimensional (3D) echocardiographic reconstruction has potential advantages for assessing aneurysmal left ventricles because it is not dependent on geometric assumptions, does not require standardized views that may exclude portions of the aneurysm, and can potentially measure separate aneurysm and nonaneurysm cavity volumes of any shape. The purpose of this study was first, to validate the accuracy of 3D echocardiographic reconstruction for quantifying total LV and separate LV body and aneurysm volumes in vitro so as to provide direct standards for the separate volumes; and second, to determine the feasibility and accuracy of 3D echocardiographic reconstruction for quantifying the total volume and function of aneurysmal left ventricles in an animal model, providing a reference standard for instantaneous LV volume.

METHODS AND RESULTS

A recently developed 3D system that automatically combines 2D images and their locations was applied (1) to reconstruct 10 aneurysmal ventricular phantoms and 12 gel-filled autopsied human hearts with aneurysms, comparing cavity volumes (total and aneurysm) to those measured by fluid displacement; and (2) to reconstruct the left ventricle during 19 hemodynamic stages in four dogs with surgically created LV aneurysms, comparing total volumes with actual instantaneous values measured by an intracavitary balloon attached to an external column for validation and also calculating the stroke volume wasted by aneurysmal dyskinesis. 3D reconstruction reproduced the distorted aneurysmal LV shapes. In vitro, calculated volumes (aneurysm, nonaneurysm, and total) agreed well with actual values, with correlation coefficients of .99 and SEEs of 3.2 to 6.1 cm3 for phantoms and 3.4 to 4.2 cm3 for autopsied hearts (mean error, < 4% for both). In vivo, LV end-diastolic, end-systolic, and stroke volumes as well as ejection fraction calculated by 3D echocardiography correlated well with actual values (r = .99, .99, .95, and .99, respectively) and agreed closely with them (SEE = 4.3 cm3, 3.5 cm3, 1.7 cm3, and 2%, respectively). The stroke volumes wasted by the aneurysm were -20.1 +/- 19.3% of LV body (nonaneurysm) stroke volume.

CONCLUSIONS

Despite distorted ventricular shapes, a recently developed 3D echocardiographic system and surfacing algorithm can accurately reconstruct aneurysmal left ventricles and quantify total LV volume (validated in vivo and in vitro) as well as the separate volumes of the aneurysm and residual LV body (validated in vitro). This should improve our ability to evaluate such ventricles and guide surgical approaches.

Ultrasonic three-dimensional reconstruction of the heart

The recent advances in ultrasound equipment, digital image acquisition, and display techniques made three-dimensional (3D) echocardiography a clinically feasible and exciting technique which allows objective analysis of structure and pathological conditions of complex geometry. In this report, different image acquisition techniques are described and compared. In our experience, with rotational scanning the acquisition of cross-sections for 3D reconstruction becomes an integral part of a routine diagnostic study, both with a multiplane transesophageal imaging transducer, and in precordial echocardiography. After digital reformatting and image processing, a volumetric data set is obtained, which allows the display of synthetic cross-sections in various orientations independent from the point of origin of the sector scan [anyplane two-dimensional (2D) imaging]. This also offers the possibility of volume quantification, without the assumption of theoretical geometrical model of the cavity. Finally, dynamic volume rendered display can be applied for the objective display of the anatomy and the complex relationship among the different structures.

A new method for echocardiographic computerized three-dimensional reconstruction of left ventricular endocardial surface: in vitro accuracy and clinical repeatability of volumes

This study evaluates the in vitro accuracy and clinical repeatability of volumes derived by a new algorithm for three-dimensional reconstruction of cavity surfaces based on echocardiographic apical images obtained by probe rotation. The accuracy of the method was tested in latex phantoms (true volumes, 32 to 349 cm3) with (n = 9) or without (n = 9) rotational symmetry around the midcavitary long axis. Repeatability of left ventricular volumes was assessed in subjects without (n = 5) or with (n = 10) myocardial disease. Estimated phantom volumes obtained from four (three) imaging planes were close to true volumes with a mean difference +/- SD of 0 +/- 2 (2 +/- 3) cm3 in symmetric and 1 +/- 3 (4 +/- 4) cm3 in asymmetric objects. Biplane and single-plane volume estimates were less accurate. Interobserver and intraobserver repeatability of three-dimensional left ventricular volumes was good for analysis (coefficients of variation: 3.5% to 6.2%) and was lower for recording (coefficients of variation: 7.4% to 10.9%). Hence the present algorithm reproduces volumes of symmetric and deformed in vitro objects accurately over a wide range of size and shape, and it produces repeatable left ventricular volumes in the clinical situation.

Three-dimensional imaging of cardiac mass lesions by transesophageal echocardiographic computed tomography

Three-dimensional echocardiography is a new imaging technique that allows more realistic visualization of cardiac morphology. This study presents data about the diagnostic potentials of this technique concerning cardiac mass lesions, as well as its feasibility in clinical application. After the conventional investigation, multiple cross-sectional images were obtained during automatic forward advancement of a monoplane transducer mounted on a transesophageal probe. Three-dimensional reconstruction and volume determination were performed off line. Twenty-four patients were studied. In 14 cases results of echocardiographic computed tomography (echo-CT) were compared with those of monoplane/biplane transesophageal echocardiography. In 23 patients a conventional transesophageal investigation with the echo-CT probe and in 20 patients tomographic scanning were possible. Data acquisition required 12 +/- 4 minutes and three-dimensional reconstruction required 35 +/- 14 minutes. In 13 patients mass lesions were found; in 11 of 13 patients echo-CT provided diagnostic information about the precise spatial orientation and morphology of cardiac structures that could not be obtained by monoplane/biplane transesophageal echocardiography. The technique revealed accurate distance measurements and volume determination of mass lesions. Echo-CT is a further step toward the application of clinically useful three-dimensional echocardiography.

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

OBJECTIVES

This study aimed to validate a method for mass computation in vitro and in vivo and to compare it with conventional methods.

BACKGROUND

Conventional 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.

METHODS

Eleven 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.

RESULTS

In 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).

CONCLUSIONS

Image 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.

Clinical application of three-dimensional transesophageal echocardiography

Three-dimensional transesophageal echocardiography is a new and evolving cardiac imaging technique. We reported our experiences of its clinical applications in 59 patients. A series of special temporal longitudinal views were selected by the frame grabber. Then the computer connected each digitized endocardial surface of the longitudinal views according to their spatial position and reconstructed the three-dimensional, cardiac shaded picture with gray scale. The three-dimensional transesophageal echocardiographic images were divided into three areas. The right area was right anterior to the esophagus and included such structures as the superior vena cava, right atrium, interatrial septum, and left atrium; the size, shape, and location of an atrial septal defect could be clearly shown. In the middle area the origin and the course of the two great arteries could be visualized, thus facilitating the diagnosis of transposition of the great arteries; in patients with obstruction of the right ventricular outflow tract, the circular ridgelike narrowing in the right ventricle was clearly visualized. In the left area the contour and size of the left ventricle and left atrium and the shape and point of coaptation of the mitral valve could be demonstrated; in patients with mitral valve prolapse, part of either leaflet protruded into the left atrium and appeared as a spoonlike depression in the mitral valve. Other entities subjected to three-dimensional transesophageal echocardiographic reconstruction included cor triatriatum, left atrial myxoma, aneurysm of sinus of Valsalva, dissecting aortic aneurysm, mitral stenosis, mitral regurgitation, and mitral valve prolapse.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional echocardiography: in vivo validation for right ventricular free wall mass as an index of hypertrophy

OBJECTIVES

This study tested the ability of three-dimensional echocardiography to reconstruct the right ventricular free wall and determine its mass in vivo using a system that automatically combines two-dimensional images with their spatial locations.

BACKGROUND

Right ventricular free wall thickness is limited as an index of right ventricular hypertrophy because right ventricular mass may increase by dilation without increased thickness and because trabeculations and oblique views can exaggerate thickness in individual M-mode and two-dimensional scans. Three-dimensional echocardiography may have potential advantages because it can integrate the entire free wall mass, uninfluenced by oblique views or geometric assumptions.

METHODS

The three-dimensional system was applied to 12 beating canine hearts to reconstruct the right ventricular free wall in intersecting views. The corresponding mass was compared with actual weights of the excised right ventricular free wall (15.5 to 78 g). For comparison, right ventricular sinus and outflow tract thickness were also measured by two-dimensional echocardiography, and the ability to predict mass from these values was determined.

RESULTS

The three-dimensional algorithm successfully reproduced right ventricular free wall mass, which agreed well with actual values: y = 1.04x + 0.02, r = 0.985, SEE = 2.7 g (5.7% of the mean value). The two-dimensional predictions showed increased scatter: The variance of mass estimation, based on thickness, was 9.5 to 12.5 (average 11) times higher than the three-dimensional method (p < 0.02).

CONCLUSIONS

Despite the irregular crescentic shape of the right ventricle, its free wall mass can be accurately measured by three-dimensional echocardiography in vivo, providing closer agreement with actual mass than predictions based on wall thickness. This method, with the increased efficiency of the three-dimensional system, can potentially improve our ability to evaluate the presence and progression of right ventricular hypertrophy.

Three-dimensional echocardiography. In vivo validation for right ventricular volume and function

BACKGROUND

Current two-dimensional echocardiographic measures of right ventricular volume are limited by the asymmetrical and crescentic shape of the ventricle and by difficulty in obtaining standardized views. Three-dimensional echocardiographic reconstruction, which does not require geometric assumptions or standardized views, may therefore have potential advantages for determining right ventricular volume. Three-dimensional techniques, however, have not been applied to the right ventricle in vivo, where cardiac motion and contraction could affect accuracy. The purpose of this study was to determine the feasibility and accuracy of three-dimensional echocardiographic reconstruction for quantifying right ventricular volume and function in vivo. In particular, it was designed to test the accuracy of a newly developed system that provides rapid, efficient, and automated three-dimensional data collection (minimizing motion effects) and takes advantage of the full three-dimensional data set to obtain volume.

METHODS AND RESULTS

The three-dimensional system was applied to reconstruct the right ventricle and measure its volume and function during 20 hemodynamic stages created in five dogs. Actual instantaneous volumes were measured continuously by an intracavitary balloon connected to an external column. Hemodynamics were varied by volume loading and induction of ischemia. Three-dimensional reconstruction successfully reproduced right ventricular volume compared with actual values at end diastole (y = 1.0 chi-3.4, r = .99, SEE = 1.8 mL) and end systole (y = 1.0 chi+ 2.0, 4 = .98, SEE = 2.5 mL). The mean difference between calculated and actual volumes throughout the cycle was 2.1 mL, or 4.9% of the mean. Ejection fraction also correlated well with actual values (y = 0.96 chi-0.3, r = .98, SEE = 3.3%).

CONCLUSIONS

Despite the irregular crescentic shape of the right ventricle, this newly developed three-dimensional system and surfacing algorithm can accurately reconstruct its shape and quantitate its volume and function in vivo without geometric assumptions. The increased efficiency of the system should increase applicability to issues of clinical and research interest.