Real-time 3D Echocardiography Data Research Articles

Standardized Evaluation System for Left Ventricular Segmentation Algorithms in 3D Echocardiography.

Real-time 3D Echocardiography (RT3DE) has been proven to be an accurate tool for left ventricular (LV) volume assessment. However, identification of the LV endocardium remains a challenging task, mainly because of the low tissue/blood contrast of the images combined with typical artifacts. Several semi and fully automatic algorithms have been proposed for segmenting the endocardium in RT3DE data in order to extract relevant clinical indices, but a systematic and fair comparison between such methods has so far been impossible due to the lack of a publicly available common database. Here, we introduce a standardized evaluation framework to reliably evaluate and compare the performance of the algorithms developed to segment the LV border in RT3DE. A database consisting of 45 multivendor cardiac ultrasound recordings acquired at different centers with corresponding reference measurements from three experts are made available. The algorithms from nine research groups were quantitatively evaluated and compared using the proposed online platform. The results showed that the best methods produce promising results with respect to the experts' measurements for the extraction of clinical indices, and that they offer good segmentation precision in terms of mean distance error in the context of the experts' variability range. The platform remains open for new submissions.

Comprehensive evaluation of cardiac function and detection of myocardial infarction based on a semi-automated analysis using full-volume real time three-dimensional echocardiography.

Quantitative left ventricular mass (LVM) as well as regional strain values may be obtained from full-volume real time 3D echocardiography data via semi-automated feature tracking and represent indices of heart function, both in health and disease. Fresh adult porcine and ovine hearts were passively pumped to simulate normal cardiac motion at stroke volumes (SVs) varying from 30 to 70 mL. A 3V-D Matrix probe, interfaced with a GE Vivid E9 ultrasound system, was used to image each heart at baseline conditions and after simulated myocardial infarction (MI). The 4D LV quantification function of EchoPAC PC was used to quantify the LVM and longitudinal and circumferential strain (LS & CS) of LV segments at each SV prior and subsequent to simulated MI. LVM was validated by volumetric displacement, while LS and CS values were compared to sonomicrometry-based strain. Linear regression analyses show excellent correlations in LVM, LS, and CS between the 4D echo and volumetric/sonomicrometric displacement with R(2) values of 0.99, 0.88, and 0.67, respectively. Bland-Altman analyses for all variables validate the compatibility of both methods. It was also determined that EchoPAC PC was able to detect a decrease in LS and CS in the relevant segments between pre- and post-MI at all SVs (P < 0.05). EchoPAC PC is a robust utility with the ability to accurately obtain quantitative LVM, LS, and CS values from 4D echo volumes and has the potential to improve the yield of clinical studies in cases of suspected MI.

Real-time three-dimensional echocardiographic left ventricular systolic assessment: side-by-side comparison with 64-slice multi-detector cardiac computed tomography

To investigate by real-time 3D echocardiography (RT3DE) and cardiac computed tomography (CCT) the analysis of left ventricle ejection fraction (LVEF) and volumes. A total of 67 patients (37 males, 55 +/- 11 years) were studied prospectively by RT3DE and by 64-slice CCT. RT3DE data: LVEF ranged from 30 to 78.6% (63.1 +/- 7.33); left ventricular end-diastolic volume (LVEDV) from 44.1 to 210 (104.9 +/- 29.7) mL; left ventricular end-systolic volume (LVESV) from 11.4 to 149 ( 38.9 +/- 19.3) mL. CCT data: LVEF ranged from 28 to 86% (66 +/- 8.4); LVEDV from 51 to 212 (110.3 +/- 31.2) mL; LVESV from 7 to 152 (38.2 +/- 19.2) mL. Correlations relative to RT3DE and CCT were: LVEF (r: 0.79, P < 0.0001); LVEDV (r: 0.82, P < 0.0001); and LVESV (r: 0.91, P < 0.0001). It was observed adequate correlation between RT3DE and CCT ventricular systolic function and geometry assessment.

Quantitative assessment of left ventricular volume and ejection fraction using two-dimensional speckle tracking echocardiography

Two-dimensional speckle tracking echocardiography (2DSTE) allows measurements of left ventricular (LV) volumes and LV ejection fraction (LVEF) without manual tracings. Our goal was to determine the accuracy of 2DSTE against real-time 3D echocardiography (RT3DE) and against cardiac magnetic resonance (CMR) imaging. In Protocol 1, 2DSTE data in the apical four-chamber view (iE33, Philips) and CMR images (Philips 1.5T scanner) were obtained in 20 patients. The 2DSTE data were analysed using custom software, which automatically performed speckle tracking analysis throughout the cardiac cycle. LV volume curves were generated using the single-plane Simpson's formula, from which end-diastolic volume (LVEDV), end-systolic volume (LVESV), and LVEF were calculated. In Protocol 2, the 2DSTE and RT3DE data were acquired in 181 subjects. RT3DE data sets were acquired, and LV volumes and LVEF were measured using QLab software (Philips). In Protocol 1, excellent correlations were noted between the methods for LVEDV (r=0.95), ESV (r=0.95), and LVEF (r=0.88). In Protocol 2, LV volume waveforms suitable for analysis were obtained from 2DSTE images in all subjects. The time required for analysis was <2 min per patient. Excellent correlations were noted between the methods for LVEDV (r=0.95), ESV (r=0.97), and LVEF (r=0.92). However, 2DSTE significantly underestimated LVEDV, resulting in a mean of 8% underestimation in LVEF. Intra- and inter-observer variabilities of 2DSTE were 7 and 9% in LV volume and 6 and 8% in LVEF, respectively. Two-dimensional speckle tracking echocardiography measurements resulted in a small but significant underestimation of LVEDV and EF compared with RT3DE. However, the accuracy, low intra- and inter-observer variabilities and speed of analysis make 2DSTE a potentially useful modality for LV functional assessment in the routine clinical setting.

Measurement of cardiac output by real-time 3-D echocardiography in patients undergoing assessment for cardiac transplantation

Heart transplant assessment includes cardiac output calculation by right heart catheterisation. Real-time 3D echocardiography (RT-3DE), unlike 2D echocardiography, can measure stroke volume without inaccurate geometrical assumptions. The purpose of this study was to assess the feasibility and accuracy of non-invasive RT-3DE cardiac output calculation. Forty consecutive patients referred for transplant assessment underwent transthoracic RT-3DE. Full volume 3DE data sets were acquired from apical views with the iE33 ultrasound system (Philips Ultrasound, Bothell, USA). Four patients were excluded due to poor image quality. The remaining 36 patients had end-diastolic (LVEDV) and end-systolic (LVESV) left ventricular volumes manually traced, using endocardial detection software. Cardiac output was subsequently calculated: [(LVEDV - LVESV) x heart rate]. Thermodilution derived cardiac outputs, under the same haemodynamic conditions, were used as reference for comparison. There was close correlation between RT-3DE and catheter derived cardiac outputs (r = 0.91, y = 0.86x + 0.45, SEE 0.39 L/min, mean difference from reference -0.06 L/min, SD 0.40 L/min). RT-3DE data analysis took 3 min per case. This study shows RT-3DE is an accurate method for calculating cardiac output. In patients requiring serial evaluation of cardiac function, this non-invasive test may be preferable to invasive right heart catheterisation.

Quantitative Assessment of Left Ventricular Size and Function

Cardiac CT (CCT) and real-time 3D echocardiography (RT3DE) are being used increasingly in clinical cardiology. CCT offers superb spatial and contrast resolution, resulting in excellent endocardial definition. RT3DE has the advantages of low cost, portability, and live 3D imaging without offline reconstruction. We sought to compare both CCT and RT3DE measurements of left ventricular size and function with the standard reference technique, cardiac MR (CMR). In 31 patients, RT3DE data sets (Philips 7500) and long-axis CMR (Siemens, 1.5 T) and CCT (Toshiba, 16-slice MDCT) images were obtained on the same day without beta-blockers. All images were analyzed to obtain end-systolic and end-diastolic volumes and ejection fractions using the same rotational analysis to eliminate possible analysis-related differences. Intertechnique agreement was tested through linear regression and Bland-Altman analyses. Repeated measurements were performed to determine intraobserver and interobserver variability. Both CCT and RT3DE measurements resulted in high correlation (r2 > 0.85) compared with CMR. However, CCT significantly overestimated end-diastolic and end-systolic volumes (26 and 19 mL; P < 0.05), resulting in a small but significant bias in ejection fraction (-2.8%). RT3DE underestimated end-diastolic and end-systolic volumes only slightly (5 and 6 mL), with no significant bias in EF (0.3%; P = 0.68). The limits of agreement with CMR were comparable for the 2 techniques. The variability in the CCT measurements was roughly half of that in either RT3DE or CMR values. CCT provides highly reproducible measurements of left ventricular volumes, which are significantly larger than CMR values. RT3DE measurements compared more favorably with the CMR reference, albeit with higher variability.

Real-Time Three-Dimensional Echocardiography

Left ventricular (LV) mechanical dyssynchrony (LVMD) has emerged as a therapeutic target using cardiac resynchronization therapy (CRT) in selected patients with chronic heart failure. Current methods used to evaluate LVMD are technically difficult and do not assess LVMD of the whole LV simultaneously. We developed and validated real-time 3D echocardiography (RT3DE) as a novel method to assess global LVMD. Eighty-nine healthy volunteers and 174 unselected patients referred for routine echocardiography underwent 2D echocardiography and RT3DE. RT3DE data sets provided time-volume analysis for global and segmental LV volumes. A systolic dyssynchrony index (SDI) was derived from the dispersion of time to minimum regional volume for all 16 LV segments. Healthy subjects and patients with normal LV systolic function had highly synchronized segmental function (SDI, 3.5+/-1.8% and 4.5+/-2.4%; P=0.7). SDI increased with worsening LV systolic function regardless of QRS duration (mild, 5.4+/-0.83%; moderate, 10.0+/-2%; severe LV dysfunction, 15.6+/-1%; P for trend <0.001). We found that 37% of patients with moderate to severe LV systolic dysfunction had significant dyssynchrony with normal QRS durations (SDI, 14.7+/-1.2%). Twenty-six patients underwent CRT. At long-term follow-up, responders demonstrated reverse remodeling after CRT with a significant reduction in SDI (16.9+/-1.1% to 6.9+/-1%; P<0.0001) and end-diastolic volume (196.6+/-17.3 to 132.1+/-13.5 mL; P<0.0001) associated with an increase in LV ejection fraction (17+/-2.2% to 31.6+/-2.9%; P<0.0001). RT3DE can quantify global LVMD in patients with and without QRS prolongation. RT3DE represents a novel technique to identify chronic heart failure patients who may otherwise not be considered for CRT.