The use of live three-dimensional Doppler echocardiography in the measurement of cardiac output

Color Flow Ultrasound Spatial Sampling Beam Density for Partial Volume-Corrected Three-Dimensional Volume Flow (3DVF): Theory, Simulation, and Experiment

OBJECTIVE

The purpose of this study was to quantify the accuracy of partial volume-corrected three-dimensional volume flow (3DVF) measurements as a function of spatial sampling beam density using carefully-designed parametric analyses in order to inform the target applications of 3DVF.

METHODS

Experimental investigations employed a mechanically-swept curvilinear ultrasound array to acquire 3D color flow (6.3 MHz) images in flow phantoms consisting of four lumen diameters (6.35, 4.88, 3.18 and 1.65 mm) with volume flow rates of 440, 260, 110 and 30 mL/min, respectively. Partial volume-corrected three-dimensional volume flow (3DVF) measurements, based on the Gaussian surface integration principle, were computed at five regions of interest positioned between depths of 2 and 6 cm in 1 cm increments. At each depth, the color flow beam point spread function (PSF) was also determined, using in-phase/quadrature data, such that 3DVF bias could then be related to spatial sampling beam density. Corresponding simulations were performed for a laminar parabolic flow profile that was sampled using the experimentally-measured PSFs. Volume flow was computed for all combinations of lumen diameters and the PSFs at each depth.

RESULTS

Accurate 3DVF measurements, i.e., bias less than ±20%, were achieved for spatial sampling beam densities where at least 6 elevational color flow beams could be positioned across the lumen. In these cases, greater than 8 lateral color flow beams were present. PSF measurements showed an average lateral-to-elevational beam width asymmetry of 1:2. Volume flow measurement bias increased as the color flow beam spatial sampling density within the lumen decreased.

CONCLUSION

Applications of 3DVF, particularly those in the clinical domain, should focus on areas where a spatial sampling density of 6 × 6 (lateral x elevational) beams can be realized in order to minimize measurement bias. Matrix-based ultrasound arrays that possess symmetric PSFs may be advantageous to achieve adequate beam densities in smaller vessels.

Research on Digital Technology Use in Cardiology: Bibliometric Analysis

Background

Digital technology uses in cardiology have become a popular research focus in recent years. However, there has been no published bibliometric report that analyzed the corresponding academic literature in order to derive key publishing trends and characteristics of this scientific area.

Objective

We used a bibliometric approach to identify and analyze the academic literature on digital technology uses in cardiology, and to unveil popular research topics, key authors, institutions, countries, and journals. We further captured the cardiovascular conditions and diagnostic tools most commonly investigated within this field.

Methods

The Web of Science electronic database was queried to identify relevant papers on digital technology uses in cardiology. Publication and citation data were acquired directly from the database. Complete bibliographic data were exported to VOSviewer, a dedicated bibliometric software package, and related to the semantic content of titles, abstracts, and keywords. A term map was constructed for findings visualization.

Results

The analysis was based on data from 12,529 papers. Of the top 5 most productive institutions, 4 were based in the United States. The United States was the most productive country (4224/12,529, 33.7%), followed by United Kingdom (1136/12,529, 9.1%), Germany (1067/12,529, 8.5%), China (682/12,529, 5.4%), and Italy (622/12,529, 5.0%). Cardiovascular diseases that had been frequently investigated included hypertension (152/12,529, 1.2%), atrial fibrillation (122/12,529, 1.0%), atherosclerosis (116/12,529, 0.9%), heart failure (106/12,529, 0.8%), and arterial stiffness (80/12,529, 0.6%). Recurring modalities were electrocardiography (170/12,529, 1.4%), angiography (127/12,529, 1.0%), echocardiography (127/12,529, 1.0%), digital subtraction angiography (111/12,529, 0.9%), and photoplethysmography (80/12,529, 0.6%). For a literature subset on smartphone apps and wearable devices, the Journal of Medical Internet Research (20/632, 3.2%) and other JMIR portfolio journals (51/632, 8.0%) were the major publishing venues.

Conclusions

Digital technology uses in cardiology target physicians, patients, and the general public. Their functions range from assisting diagnosis, recording cardiovascular parameters, and patient education, to teaching laypersons about cardiopulmonary resuscitation. This field already has had a great impact in health care, and we anticipate continued growth.

Anatomical description of the skulls of peccaries (Tayassu tajacu, Linnaeus 1758) by computed tomography

ABSTRACT The aim of this study was to evaluate the anatomical structures of the skulls of peccaries to establish the basis for their clinical study and future preclinical research. Ten skulls of adult peccaries were subjected to tomographic examination. The data obtained were processed via three-dimensional image reconstruction software (3D images). The reconstructions obtained from the neurocranium of the studied specimens allowed the identification and description of the following structures: nasal bone, frontal bone, parietal bones, incisor bone, maxillary bone, zygomatic bone, temporal bone, palatal bone, occipital bone, vomer bone, pterygoid bone, sphenoid bone, paranasal sinuses and orbit. Computed tomography proved to be an important diagnostic tool in the investigation of the skull of this species, allowing the acquisition of anatomical values not yet documented for the species in the literature.

Comparison of Variations Between Spectral Doppler and Gaussian Surface Integration Methods for Umbilical Vein Blood Volume Flow

OBJECTIVES

We are studying a new method for estimating blood volume flow that uses 3-dimensional ultrasound to measure the total integrated flux through an ultrasound-generated Gaussian surface that intersects the umbilical cord. This method makes none of the assumptions typically required with standard 1-dimensional spectral Doppler volume flow estimates. We compared the variations in volume flow estimates between techniques in the umbilical vein.

METHODS

The study was Institutional Review Board approved, and all 12 patients gave informed consent. Because we had no reference standard for the true umbilical vein volume flow, we compared the variations of the measurements for the flow measurement techniques. At least 3 separate spectral Doppler and 3 separate Gaussian surface measurements were made along the umbilical vein. Means, standard deviations, and coefficients of variation (standard deviation/mean) for the flow estimation techniques were calculated for each patient. P < .05 was considered significant.

RESULTS

The ranges of the mean volume flow estimates were 174 to 577 mL/min for the spectral Doppler method and 100 to 341 mL/min for the Gaussian surface integration (GSI) method. The mean standard deviations (mean ± SD) were 161 ± 95 and 45 ± 48 mL/min for the spectral Doppler and GSI methods, respectively (P < .003). The mean coefficients of variation were 0.46 ± 0.17 and 0.18 ± 0.14 for the spectral Doppler and GSI methods respectively (P < 0.002).

CONCLUSIONS

The new volume flow estimation method using 3-dimensional ultrasound appears to have significantly less variation in estimates than the standard 1-dimensional spectral Doppler method.

In Vivo Validation of Volume Flow Measurements of Pulsatile Flow Using a Clinical Ultrasound System and Matrix Array Transducer

The goal of this study was to evaluate the accuracy of a non-invasive C-plane Doppler estimation of pulsatile blood flow in the lower abdominal vessels of a porcine model. Doppler ultrasound measurements from a matrix array transducer system were compared with invasive volume flow measurements made on the same vessels with a surgically implanted ultrasonic transit-time flow probe. For volume flow rates ranging from 60 to 750 mL/min, agreement was very good, with a Pearson correlation coefficient of 0.97 (p < 0.0001) and a mean bias of -4.2%. The combination of 2-D matrix array technology and fast processing gives this Doppler method clinical potential, as many of the user- and system-dependent parameters of previous methods, including explicit vessel angle and diameter measurements, are eliminated.

Automatic quantification of aortic regurgitation using 3D full volume color doppler echocardiography: a validation study with cardiac magnetic resonance imaging

Recent advances in real-time three-dimensional (3D) echocardiography provide the automated measurement of mitral inflow and aortic stroke volume without the need to assume the geometry of the heart. The aim of this study is to explore the ability of 3D full volume color Doppler echocardiography (FVCDE) to quantify aortic regurgitation (AR). Thirty-two patients with more than a moderate degree of AR were enrolled. AR volume was measured by (1) two-dimensional-CDE, using the proximal isovelocity surface area (PISA) and (2) real-time 3D-FVCDE with (3) phase-contrast cardiac magnetic resonance imaging (PC-CMR) as the reference method. Automated AR quantification using 3D-FVCDE was feasible in 30 of the 32 patients. 2D-PISA underestimated the AR volume compared to 3D-FVCDE and PC-CMR (38.6 ± 9.9 mL by 2D-PISA; 49.5 ± 10.2 mL by 3D-FVCDE; 52.3 ± 12.6 mL by PC-CMR). The AR volume assessed by 3D-FVCDE showed better correlation and agreement with PC-CMR (r = 0.93, p < 0.001, 2SD: 9.5 mL) than did 2D-PISA (r = 0.76, p < 0.001, 2SD: 15.7 mL). When used to classify AR severity, 3D-FVCDE agreed better with PC-CMR (k = 0.94) than did 2D-PISA (k = 0.53). In patients with eccentric jets, only 30% were correctly graded by 2D-PISA. Conversely, almost all patients with eccentric jets (86.7%) were correctly graded by 3D-FVCDE. In patients with multiple jets, only 3 out of 10 were correctly graded by 2D-PISA, while 3D-FVCDE correctly graded 9 out of 10 of these patients. Automated quantification of AR using the 3D-FVCDE method is clinically feasible and more accurate than the current 2D-based method. AR quantification by 2D-PISA significantly misclassified AR grade in patients with eccentric or multiple jets. This study demonstrates that 3D-FVCDE is a valuable tool to accurately measure AR volume regardless of AR characteristics.

Quantitative assessment of mitral inflow and aortic outflow stroke volumes by 3-dimensional real-time full-volume color flow doppler transthoracic echocardiography: an in vivo study

OBJECTIVES

Noninvasive quantification of left ventricular (LV) stroke volumes has an important clinical role in assessing circulation and monitoring therapeutic interventions for cardiac disease. This study validated the accuracy of a real-time 3-dimensional (3D) color flow Doppler method performed during transthoracic echocardiography (TTE) for quantifying volume flows through the mitral and aortic valves using a dedicated offline 3D flow computation program compared to LV sonomicrometry in an open-chest animal model.

METHODS

Forty-six different hemodynamic states in 5 open-chest pigs were studied. Three-dimensional color flow Doppler TTE and 2-dimensional (2D) TTE were performed by epicardial scanning. The dedicated software was used to compute flow volumes at the mitral annulus and the left ventricular outflow tract (LVOT) with the 3D color flow Doppler method. Stroke volumes by 2D TTE were computed in the conventional manner. Stroke volumes derived from sonomicrometry were used as reference values.

RESULTS

Mitral inflow and LVOT outflow derived from the 3D color flow Doppler method correlated well with stroke volumes by sonomicrometry (R = 0.96 and 0.96, respectively), whereas correlation coefficients for mitral inflow and LVOT outflow computed by 2D TTE and stroke volumes by sonomicrometry were R = 0.84 and 0.86. Compared to 2D TTE, the 3D method showed a smaller bias and narrower limits of agreement in both mitral inflow (mean ± SD: 3D, 2.36 ± 2.86 mL; 2D, 10.22 ± 8.46 mL) and LVOT outflow (3D, 1.99 ± 2.95 mL; 2D, 4.12 ± 6.32 mL).

CONCLUSIONS

Real-time 3D color flow Doppler quantification is feasible and accurate for measurement of mitral inflow and LVOT outflow stroke volumes over a range of hemodynamic conditions.

Evaluation of a new 3-dimensional color Doppler flow method to quantify flow across the mitral valve and in the left ventricular outflow tract: an in vitro study

OBJECTIVES

The aim of this study was to assess the accuracy, feasibility, and reproducibility of determining stroke volume from a novel 3-dimensional (3D) color Doppler flow quantification method for mitral valve (MV) inflow and left ventricular outflow tract (LVOT) outflow at different stroke volumes when compared with the actual flow rate in a pumped porcine cardiac model.

METHODS

Thirteen freshly harvested pig hearts were studied in a water tank. We inserted a latex balloon into each left ventricle from the MV annulus to the LVOT, which were passively pumped at different stroke volumes (30-80 mL) using a calibrated piston pump at increments of 10 mL. Four-dimensional flow volumes were obtained without electrocardiographic gating. The digital imaging data were analyzed offline using prototype software. Two hemispheric flow-sampling planes for color Doppler velocity measurements were placed at the MV annulus and LVOT. The software computed the flow volumes at the MV annulus and LVOT within the user-defined volume and cardiac cycle.

RESULTS

This novel 3D Doppler flow quantification method detected incremental increases in MV inflow and LVOT outflow in close agreement with pumped stroke volumes (MV inflow, r = 0.96; LVOT outflow, r = 0.96; P < .01). Bland-Altman analysis demonstrated overestimation of both (MV inflow, 5.42 mL; LVOT outflow, 4.46 mL) with 95% of points within 95% limits of agreement. Interobserver variability values showed good agreement for all stroke volumes at both the MV annulus and LVOT.

CONCLUSIONS

This study has shown that the 3D color Doppler flow quantification method we used is able to compute stroke volumes accurately at the MV annulus and LVOT in the same cardiac cycle without electrocardiographic gating. This method may be valuable for assessment of cardiac output in clinical studies.

Automated quantification of mitral regurgitation by three dimensional real time full volume color Doppler transthoracic echocardiography: a validation with cardiac magnetic resonance imaging and comparison with two dimensional quantitative methods

BACKGROUND

Accurate assessment of mitral regurgitation (MR) severity is crucial for clinical decision-making and optimizing patient outcomes. Recent advances in real-time three dimensional (3D) echocardiography provide the option of real-time full volume color Doppler echocardiography (FVCD) measurements. This makes it practical to quantify MR by subtracting aortic stroke volume from the volume of mitral inflow in an automated manner.

METHODS

Thirty-two patients with more than a moderate degree of MR assessed by transthoracic echocardiography (TTE) were consecutively enrolled during this study. MR volume was measured by 1) two dimensional (2D) Doppler TTE, using the proximal isovelocity surface area (PISA) and the volumetric quantification methods (VM). Then, 2) real time 3D-FVCD was subsequently obtained, and dedicated software was used to quantify the MR volume. MR volume was also measured using 3) phase contrast cardiac magnetic resonance imaging (PC-CMR). In each patient, all these measurements were obtained within the same day. Automated MR quantification was feasible in 30 of 32 patients.

RESULTS

The mean regurgitant volume quantified by 2D-PISA, 2D-VM, 3D-FVCD, and PC-CMR was 72.1 ± 27.7, 79.9 ± 36.9, 69.9 ± 31.5, and 64.2 ± 30.7 mL, respectively (p = 0.304). There was an excellent correlation between the MR volume measured by PC-CMR and 3D-FVCD (r = 0.85, 95% CI 0.70-0.93, p < 0.001). Compared with PC-CMR, Bland-Altman analysis for 3D-FVCD showed a good agreement (2 standard deviations: 34.3 mL) than did 2D-PISA or 2D-VM (60.0 and 62.8 mL, respectively).

CONCLUSION

Automated quantification of MR with 3D-FVCD is feasible and accurate. It is a promising tool for the real-time 3D echocardiographic assessment of patients with MR.

WEB downloadable software for training in cardiovascular hemodynamics in the (3-D) stress echo lab

When a physiological (exercise) stress echo is scheduled, interest focuses on wall motion segmental contraction abnormalities to diagnose ischemic response to stress, and on left ventricular ejection fraction to assess contractile reserve. Echocardiographic evaluation of volumes (plus standard assessment of heart rate and blood pressure) is ideally suited for the quantitative and accurate calculation of a set of parameters allowing a complete characterization of cardiovascular hemodynamics (including cardiac output and systemic vascular resistance), left ventricular elastance (mirroring left ventricular contractility, theoretically independent of preload and afterload changes heavily affecting the ejection fraction), arterial elastance, ventricular arterial coupling (a central determinant of net cardiovascular performance in normal and pathological conditions), and diastolic function (through the diastolic mean filling rate). All these parameters were previously inaccessible, inaccurate or labor-intensive and now become, at least in principle, available in the stress echocardiography laboratory since all of them need an accurate estimation of left ventricular volumes and stroke volume, easily derived from 3 D echo.

Aims of this paper are: 1) to propose a simple method to assess a set of parameters allowing a complete characterization of cardiovascular hemodynamics in the stress echo lab, from basic measurements to calculations 2) to propose a simple, web-based software program, to learn and training calculations as a phantom of the everyday activity in the busy stress echo lab 3) to show examples of software testing in a way that proves its value.

The informatics infrastructure is available on the web, linking to http://cctrainer.ifc.cnr.it

A novel operator-independent algorithm for cardiac output measurements based on three-dimensional transoesophageal colour Doppler echocardiography

AIMS

Cardiac output (CO) measurements from three-dimensional (3D) trans-mitral Doppler echocardiography are prone to error as manual selection of the region of interest (i.e. the site of measurement) is required. We newly developed an automated, user-independent algorithm to select the site of colour Doppler CO measurement. We aimed to validate this new method by benchmarking it against thermodilution, the current gold standard for CO measurements.

METHODS AND RESULTS

Transoesophageal colour 3D Doppler echocardiographic studies were obtained from 15 patients who also had received a pulmonary catheter for invasive CO measurements. Trans-mitral flow was determined using a novel operator-independent algorithm to automatically select the optimal site of measurement. The operator-independent CO measurements were referenced against thermodilution. A good correlation was found between operator-independent Doppler flow computations and thermodilution with a mean bias of 0.09 L/min, standard deviation of bias 1.3 L/min, and a 26% error (2 SD/mean CO). Mean CO was 4.94 L/min (range 3.10-7.10 L/min).

CONCLUSION

Our findings demonstrate that CO computation from transoesophageal colour 3D Doppler echo can be automated concerning the site of velocity measurement. Our operator-independent algorithm provides an objective and reproducible alternative to thermodilution.

Haemodynamics and blood flow measured using ultrasound imaging

Visualization of, and measurements related to, haemodynamic phenomena in arteries may be made using ultrasound systems. Most ultrasound technology relies on simple measurements of blood velocity taken from a single site, such as the peak systolic velocity for assessment of the degree of lumen reduction caused by an arterial stenosis. Real-time two-dimensional (2D) flow field visualization is possible using several methods, such as colour flow, blood flow imaging, and echo particle image velocimetry; these have applications in the examination of the flow field in diseased arteries and in heart chambers. Three-dimensional (3D) and four-dimensional ultrasound systems have been described. These have been used to provide 2D velocity profile data for the estimation of volumetric flow. However, they are limited for haemodynamic evaluation in that they provide only one component of the velocity. The provision of all seven components (three space, three velocity, and one time) is possible using image-guided modelling, in which 3D ultrasound is combined with computational fluid dynamics. This method also allows estimation of turbulence data and of relevant quantities such as the wall shear stress.

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.

Assessing aortic valve area in aortic stenosis by continuity equation: a novel approach using real-time three-dimensional echocardiography

AIMS

Two-dimensional echocardiographic (2DE) continuity-equation derived aortic valve area (AVA) in aortic stenosis (AS) relies on non-simultaneous measurement of left ventricular outflow tract (LVOT) velocity and geometric assumptions of LVOT area, which can amplify error, especially in upper septal hypertrophy (USH). We hypothesized that real-time three-dimensional echocardiography (RT3DE) can improve accuracy of AVA by directly measuring LVOT stroke volume (SV) in one window.

METHODS AND RESULTS

RT3DE colour Doppler and 2DE were acquired in 68 AS patients (74 +/- 12 yrs) prospectively. SV was derived from flow obtained from a sampling curve placed orthogonal to LVOT (Tomtec Imaging). Agreement between continuity-equation derived AVA by RT3DE (AVA(3D-SV)) and 2DE (AVA(2D)) and predictors of discrepancies were analysed. Validation of LVOT SV was performed by aortic flow probe in a sheep model with balloon inflation of septum to mimic USH. There was only modest correlation between AVA(2D) and AVA(3D-SV) (r = 0.71, difference 0.11 +/- 0.23 cm(2)). The degree of USH was significantly associated with difference in AVA calculation (r = 0.4, P = 0.005). In experimentally distorted LVOT geometry in sheep, RT3DE correlated better with flow probe assessment (r = 0.96, P < 0.001) than 2DE (r = 0.71, P = 0.006).

CONCLUSION

RT3DE colour Doppler-derived LVOT SV in the calculation of AVA by continuity equation is more accurate than 2D, including in situations such as USH, common in the elderly, which modify LVOT geometry.

Measurement of Volumetric Flow by Real-time 3-Dimensional Doppler Echocardiography in Children

BACKGROUND

We sought to assess the accuracy and reproducibility of an automated real-time (RT) 3-dimensional (3D) Doppler echocardiography (RT3DDE) technique for measuring volumetric flow (VF) in children.

METHODS

A total of 19 healthy children (age = 11.5 +/- 3.5 years) were studied to measure VF through mitral valve (MV), aortic valve (AV), pulmonary valve (PV), and tricuspid valve (TV) by RT3DDE. RT 3D echocardiography was also performed to measure left ventricular (LV) end-systolic volume, LV end-diastolic volume, and stroke volume (stroke volume = LV end-diastolic volume--LV end-systolic volume), which served as a reference standard for comparison with VF by RT3DDE.

RESULTS

Compared with stroke volume by RT 3D echocardiography, the correlation with VF was excellent for MV (r = 0.91), good for AV (r = 0.89) and PV (r = 0.89), but poor for TV (r = 0.20) by RT3DDE. There were good agreements for AV (bias = 0.9 +/- 5.0 mL), PV (bias = -0.4 +/- 5.7 mL), and MV (bias = 4.1 +/- 4.7 mL), and marked underestimation for TV (bias = -24.4 +/- 14.6 mL).

CONCLUSIONS

Our data demonstrated that VF measurement by RT3DDE is feasible and reasonably accurate for MV, AV, and PV but problematic for TV.

Current Status of Three-Dimensional Color Flow Doppler

Three-dimensional (3D) color Doppler echocardiography is a relatively new noninvasive tool that displays and quantitates regurgitant flow and also enables estimation of cardiac output, stroke volume, pulmonary outflow, and shunt calculations. This article provides an overview of the current methodology of 3D color flow, and its advantages and limitations.

Use of 3-Dimensional Color Doppler Echocardiography to Measure Stroke Volume in Human Beings: Comparison with Thermodilution

BACKGROUND

The availability of accurate noninvasive measurements of cardiac output (CO) would be useful in assessing disease severity and the effects of therapeutic interventions in many different clinical settings. Current noninvasive methods are limited by their dependence on geometric assumptions. We tested the feasibility of a new technique for CO measurements based on 3-dimensional color Doppler echocardiographic (3D-CD) imaging.

OBJECTIVE

We sought to compare the accuracy of CO determination in human beings as measured by 3D-CD and conventional 2-dimensional echocardiography (2DE) using thermodilution as the gold standard for comparison.

METHODS

Simultaneous 3D-CD, 2DE, and thermodilution data were acquired in 47 patients postcardiac transplantation with good acoustic windows who required routine hemodynamic evaluation with a pulmonary artery catheter. Data were stored on compact disc and analyzed offline using custom software. Echocardiographic data were compared against thermodilution using linear regression and Bland-Altman analysis.

RESULTS

Correlation coefficients for 3D-CD and 2DE of the left ventricular outflow tract were r = 0.94 and r = 0.78, respectively. Correlation coefficients for 3D-CD and 2DE of the mitral valve were r = 0.93 and r = 0.75, respectively. Compared with 2DE, 3D-CD demonstrated a smaller bias and narrower limits of agreement in the left ventricular outflow tract (-1.84 +/- 16.8 vs -8.6 +/- 36.2 mL) and mitral valve inflow (-0.2 +/- 15.6 vs 10.0 +/- 26 mL).

CONCLUSION

The 3D-CD determination of CO is feasible and accurate. Compared with previous noninvasive modalities, 3D-CD has the advantages of independence of geometric assumptions and ease of image acquisition and analysis.

Left ventricular volume and function in cynomolgus monkeys using real-time three-dimensional echocardiography

BACKGROUND

The purpose of this study was to investigate the feasibility of evaluating cardiac function by real time three-dimensional (RT3D) echocardiography in isoflurane-anesthetized male cynomolgus monkeys. Additionally differences between inhibitory effects of beta-blockers and a Ca channel blocker on left ventricular (LV) function were examined.

METHODS AND RESULTS

End-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) in the control (without any drug effect) were not significantly changed by repetitive measurement at a 30-day interval. Propranolol and metoprolol (0.1 and 0.3 mg/kg/10 minutes, i.v.) caused a dose-dependent increase in ESV, but little effect on EDV, resulting in a decrease in EF. Verapamil (0.1 and 0.3 mg/kg/10 minutes, i.v.) increased both EDV and ESV, but decreased EF was noted at 0.3 mg/kg.

CONCLUSIONS

These results demonstrate the feasibility of RT3D echocardiography in providing reproducible estimations of LV volume and EF in monkeys when evaluating drugs that may affect cardiac function.

Actualización en técnicas de imagen cardiaca. Ecocardiografía, resonancia magnética en cardiología y tomografía computarizada con multidetectores

This article contains a review of the most significant publications on non-invasive recent cardiac imaging techniques in 2005. The increasing importance of technological innovation in echocardiography is reflected in the sections on three dimensional echocardiography, contrast echocardiography, and myocardial deformation measurement techniques (i.e., strain echocardiography). The most important developments affecting cardiology in the techniques of magnetic resonance imaging and multidetector computed tomography are also summarized. This review ends with a detailed description of the contributions made by imaging techniques to the diagnosis of aortic disease.

Real-time Three-dimensional Color Doppler Echocardiography Overcomes the Inaccuracies of Spectral Doppler for Stroke Volume Calculation

Real-time 3-dimensional echocardiography is increasingly used in clinical cardiology. Studies have been shown that this technique can be accurately used to assess both cardiac mass and chamber volumes. We review the work showing that real-time 3-dimensional Doppler echocardiography can be used to accurately calculate intracardiac flow volumes that can potentially be used to assess cardiac function, intracardiac shunt, and valve regurgitation.

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.

Education and research using experimental pigs in a medical school

Medium-sized animals such as miniature pigs are considered to be important for education and training in medical schools to master the skills required in surgical treatment. Much still remains to be done to establish total management for animal experiments using pigs. Improvement of the effective utilization of pigs is also required from the economical and ethical points of view. We have been providing a support system at a facility for experimental animals in a medical school for 3 years, and herein we introduce our personal experiments as an instructional lecture. Before starting surgical training using live pigs, sufficient education concerning animal ethics and dry laboratory training was completed. Four kinds of miniature pigs have been used as experimental animals; porcine rearing pens have been improved and a postoperative care system has been implemented. Moreover, staff at the center offer a preoperative service of anesthesia for surgical education, training, and research. Chronic experiments have increased to represent 35% and 48% of experiments using pigs in 2003 and 2004, respectively. Experimental pigs have undergone secondary use after being killed to reduce the number of animals used in experiments. Sharing and reuse have allowed effective use of miniature pig tissues and cells for research, and have reduced the number of animals used. We recommend that researchers consider use of our total systems because they can improve the quality of medical education and research and facilitate effective use of tissues and cells by sharing and reuse among different departments.

Feasibility and Utility of Three-Dimensional Color Flow Echocardiography of the Aortic Arch: The “Echocardiographic Angiogram”

Two-dimensional transthoracic echocardiography (2DE) is the most commonly used diagnostic modality to evaluate congenital and acquired abnormalities of the aortic arch. However, 2DE is frequently limited in this ability due to the three-dimensional character of the arch and its interrelationships with other vascular structures. Recently, three-dimensional echocardiography (3DE) with 3D color flow Doppler became commercially available. We examined the feasibility and utility of 3DE with 3D color Doppler in the evaluation of patients with congenital (native and postoperative) abnormalities of the aortic arch. We found that 3DE color flow provides important diagnostic information in patients with aortic arch anomalies, in a manner that is quick and user-friendly. In addition, 17 of the 26 patients had their 3DE findings confirmed by additional modalities, providing reasonably significant validation for our findings with 3DE.

Three-dimensional geometry of the tricuspid annulus in healthy subjects and in patients with functional tricuspid regurgitation: a real-time, 3-dimensional echocardiographic study

BACKGROUND

Most rings currently used for tricuspid valve annuloplasty are formed in a single plane, whereas the actual tricuspid annulus (TA) may have a nonplanar or 3-dimensional (3D) structure. The purpose of this study was therefore to investigate the 3D geometry of the TA in healthy subjects and in patients with functional tricuspid regurgitation (TR).

METHODS AND RESULTS

This study consisted of 15 healthy subjects and 16 patients with functional TR who had real-time 3D echocardiography. With our customized software, 8 points along the TA were determined with the rotated plane around the axis at 45 degrees intervals. The TA was traced during a cardiac cycle. The distance between diagonals connecting 2 points was measured. The height was defined as the distance from the plane determined by least-squares regression analysis at all 8 points. Both the maximum (7.5+/-2.1 versus 5.6+/-1.0 cm2/m2) and minimum (5.7+/-1.3 versus 3.9+/-0.8 cm2/m2) TA areas in patients with TR were larger than those in healthy subjects (both P<0.01). Healthy subjects had a nonplanar-shaped TA with homogeneous contraction. The posteroseptal portion was the lowest toward the apex from the right atrium, and the anteroseptal portion was the highest. In patients with functional TR, the TA was dilated in the septal to lateral direction, resulting in a more circular shape than in healthy subjects. A similar 3D pattern was observed in patients with TR, but it was more planar than that in healthy subjects.

CONCLUSIONS

Real-time 3D echocardiography showed a complicated 3D structure of the TA, which appeared to be different from the "saddle-shaped" mitral annulus, suggesting an annuloplasty for TR different from that for mitral regurgitation.

Real-time 3-dimensional echocardiographic imaging of congenital heart disease using matrix-array technology: freehand real-time scanning adds instant morphologic details not well delineated by conventional 2-dimensional imaging

OBJECTIVE

We sought to investigate whether real-time (RT) 3-dimensional echocardiography (RT3D) using matrix-array technology could resolve a specific morphologic detail that could not be well resolved during conventional 2-dimensional (2D)/Doppler echocardiographic imaging of congenital heart disease.

BACKGROUND

Although 2D echocardiography is currently the primary imaging modality of congenital heart disease, there are still some anatomic details that cannot be well delineated by that modality.

METHODS

In all, 70 patients underwent RT3D examination using matrix-array transducer. Applying the standard sweeping technique as for 2D imaging, freehand RT imaging was used for immediate feedback. The 2D examinations of the last 23 consecutive patients were used to validate the additional value of RT3D by 3 examiners blinded to the findings of RT3D.

RESULTS

The adequacy of 2D imaging to resolve the morphologic detail in question ranged from 30% to 70%, whereas RT3D imaging was considered successful in delineating the morphologic detail in 80% to 100% of patients instantly. The image resolution was superior or equivalent to that obtained by 2D imaging. Heart valves, septal defects, and volumetric valvular and vascular color flow morphologies were well delineated by RT3D.

CONCLUSION

Matrix-array RT3D is a significant breakthrough technology that allowed instant visualization of cardiac anatomic details that could not be well delineated by 2D imaging. Further improvements of some technical limitations should make RT3D matrix-array cardiac imaging a significant modality in the field of echocardiographic imaging of congenital cardiac anomalies.

Real-Time 3-Dimensional Echocardiography: A Review of the Development of the Technology and Its Clinical Application

Real-time 3-dimensional echocardiography (RT3DE) is a new imaging technique that can provide accurate, important, and additional information concerning cardiovascular morphology, pathology, and function. This article will review the development of the technology of RT3DE and its clinical application. As the technique continues to evolve, RT3DE is bound to play an increasingly important role in the diagnosis, prognosis, and treatment of patients with various forms of cardiovascular disease.

Real-time 3-Dimensional Doppler Echocardiography for the Assessment of Stroke Volume: An In Vivo Human Study Compared with Standard 2-Dimensional Echocardiography

BACKGROUND

Invasive monitors and noninvasive 2-dimensional echocardiography are the standard clinical methods for stroke volume (SV) and cardiac output computation. We studied the use of real-time color Doppler 3-dimensional (3D) echocardiography (3DE) for the assessment of SV in human beings.

METHODS

In all, 55 pediatric and adult patients with good transthoracic windows and a normal aortic valve were studied. Real-time 3DE color Doppler volumes incorporating the left ventricular outflow tract and aortic valve were taken. SV was calculated from the color Doppler data in the 3DE DICOM dataset. This was compared with 2-dimensional echocardiography SV calculation from the pulsed wave velocity through the aortic valve along with the left ventricular outflow tract diameter.

RESULTS

Five patients were excluded because of mismatching of the 3D color Doppler segments in the 3D volume. The 3D Doppler volumes from the remaining 50 patients were analyzed. There was good correlation between the patients' averaged 3DE SV calculations and the 2-dimensional echocardiography pulsed wave SV estimation (y = 0.84x + 7.8, r2 = 0.90).

CONCLUSION

Real-time 3D Doppler echocardiography can be used to accurately calculate SV and cardiac output, compared with conventional pulsed Doppler measurement, in pediatric and adult patients from transthoracic imaging.

Accuracy of 3-dimensional color Doppler-derived flow volumes with increasing image depth

OBJECTIVES

We and others have reported on the use of digital color Doppler sonography from real-time 3-dimensional (3D) echocardiography and its use in accurately calculating cardiac flow volumes, namely stroke volume (SV) and, hence, cardiac output. However, in some patients, image depth is higher than average, and this may affect the accuracy of volume calculation. We sought to investigate the impact of image depth and the accompanying change in signal strength, spatial resolution, and pulse repetition frequency on the accuracy of SV calculation from 3D color Doppler data in an in vitro model.

METHODS

A tube model of the left ventricular outflow tract was constructed from plastic tubing and connected to a pulsatile pump. The volume flowing through the tube was imaged using a 3D echocardiography system. Stroke volumes from the pump were computed from the DICOM data using commercially available software and compared with a reference standard of timed volumes with the use of a graduated measuring cylinder over a range of depth settings and SVs.

RESULTS

There was good correlation between the 3D-derived SVs and the reference cylinder measures over all depths from 4 to 16 cm at 1-cm increments with a tube diameter of 17 mm, a pump rate of 60 beats/min, and SVs ranging from 20 to 70 mL. The average r(2) value for the 13 different depths was 0.976. However, the accuracy of the 3D method of volume calculation appeared to fall at depths greater than 13 cm, especially at higher SVs.

CONCLUSIONS

Stroke volume calculation from real-time 3D color Doppler data in this in vitro study shows that at depths greater than approximately 13 cm, accuracy decreases, especially at higher SVs. This may be due to decreased resolution and the reduced frame rate at these depths. At shallower depths, volume calculation form the 3D Doppler data appears very accurate.