Federico Veronesi

Volumetric Quantification of Global and Regional Left Ventricular Function From Real-Time Three-Dimensional Echocardiographic Images

Background—Real-time 3D echocardiographic (RT3DE) data sets contain dynamic volumetric information on cardiac function. However, quantification of left ventricular (LV) function from 3D echocardiographic data is performed on cut-planes extracted from the 3D data sets and thus does not fully exploit the volumetric information. Accordingly, we developed a volumetric analysis technique aimed at quantification of global and regional LV function. Methods and Results—RT3DE images obtained in 30 patients (Philips 7500) were analyzed by use of custom software based on the level-set approach for semiautomated detection of LV endocardial surface throughout the cardiac cycle, from which global and regional LV volume (LVV)–time and wall motion (WM)–time curves were obtained. The study design included 3 protocols. In protocol 1, time curves obtained in 16 patients were compared point-by-point with MRI data (linear regression and Bland-Altman analyses). Global LVV correlated highly with MRI (r=0.98; y=0.99x+2.3) with minimal bias (1.4 mL) and narrow limits of agreement (±20 mL). WM correlated highly only in basal and midventricular segments (r=0.88; y=0.85x+0.7). In protocol 2, we tested the ability of this technique to differentiate populations with known differences in LV function by studying 9 patients with dilated cardiomyopathy and 9 normal subjects. All calculated indices of global and regional systolic and diastolic LV function were significantly different between the groups. In protocol 3, we tested the feasibility of automated detection of regional WM abnormalities in 11 patients. In each segment, abnormality was detected when regional shortening fraction was below a threshold obtained in normal subjects. The automated detection agreed with expert interpretation of 2D WM in 86% of segments. Conclusions—Volumetric analysis of RT3DE data is clinically feasible and allows fast, semiautomated, dynamic measurement of LVV and automated detection of regional WM abnormalities.

A Study of Functional Anatomy of Aortic-Mitral Valve Coupling Using 3D Matrix Transesophageal Echocardiography

Background—Mitral and aortic valves are known to be coupled via fibrous tissue connecting the two annuli. Previous studies evaluating this coupling have been limited to experimental animals using invasive techniques. The new matrix array transesophageal transducer provides high-resolution real-time 3D images of both valves simultaneously. We sought to develop and test a technique for quantitative assessment of mitral and aortic valve dynamics and coupling. Methods and Results—Matrix array transesophageal (Philips iE33) imaging was performed in 24 patients with normal valves who underwent clinically indicated transesophageal echocardiography. Custom software was used to detect and track the mitral and aortic annuli in 3D space throughout the cardiac cycle, allowing automated measurement of changes in mitral and aortic valve morphology. Mitral annulus surface area and aortic annulus projected area changed reciprocally over time. Mitral annulus surface area was 8.0±2.1 cm2 at end-diastole and decreased to 7.7±2.1 cm2 in systole, reaching its maximum (10.0±2.2 cm2) at mitral valve opening. Aortic annulus projected area was 4.1±1.2 cm2 at end-diastole, then increased during isovolumic contraction reaching its maximum (4.8±1.3 cm2) in the first third of systole and its minimum (3.6±1.0 cm2) during isovolumic relaxation. The angle between the mitral and aortic annuli was maximum (136±13°) at end-diastole and decreased to its minimum value (129±11°) during systole. Conclusions—This is the first study to report quantitative 3D assessment of the mitral and aortic valve dynamics from matrix array transesophageal images and describe the mitral-aortic coupling in a beating human heart. This ability may have impact on patient evaluation for valvular surgical interventions and prosthesis design.

Mitral valve finite-element modelling from ultrasound data: a pilot study for a new approach to understand mitral function and clinical scenarios

In the current scientific literature, particular attention is dedicated to the study of the mitral valve and to comprehension of the mechanisms that lead to its normal function, as well as those that trigger possible pathological conditions. One of the adopted approaches consists of computational modelling, which allows quantitative analysis of the mechanical behaviour of the valve by means of continuum mechanics theory and numerical techniques. However, none of the currently available models realistically accounts for all of the aspects that characterize the function of the mitral valve. Here, a new computational model of the mitral valve has been developed from in vivo data, as a first step towards the development of patient-specific models for the evaluation of annuloplasty procedures. A structural finite-element model of the mitral valve has been developed to account for all of the main valvular substructures. In particular, it includes the real geometry and the movement of the annulus and papillary muscles, reconstructed from four-dimensional ultrasound data from a healthy human subject, and a realistic description of the complex mechanical properties of mitral tissues. Preliminary simulations allowed mitral valve closure to be realistically mimicked and the role of annulus and papillary muscle dynamics to be quantified.

Tracking of left ventricular long axis from real-time three-dimensional echocardiography using optical flow techniques

Two-dimensional echocardiography (2DE) is routinely used in clinical practice to measure left ventricular (LV) mass, dimensions, and function. The reliability of these measurements is highly dependent on the ability to obtain nonforeshortened long axis (LA) images of the left ventricle from transthoracic apical acoustic windows. Real time three-dimensional echocardiography (RT3DE) is a novel imaging technique that allows the acquisition of dynamic pyramidal data structures encompassing the entire ventricle and could potentially overcome the effects of LA foreshortening. Accordingly, the aim of this paper was to develop a nearly automated method based on optical flow techniques for the measurement of the left ventricular (LV) LA throughout the cardiac cycle from RT3DE data. The LV LA measurements obtained with the automated technique has been compared with LA measurements derived from manual selection of the LA from a volumetric display of RT3DE data. High correlation (r=.99,SEE=1.8%,y=.94x+5.3), no significant bias (-0.18 mm), and narrow limits of agreement (SD: 1.91 mm) were found. The comparison between the LA length derived from 2DE and RT3DE data showed significant underestimation of the 2DE based measurements. In conclusion, this study proves that RT3DE data overcome the effects of foreshortening and indicates that the method we propose allows fast and accurate quantification of LA length throughout the cardiac cycle

Myocardial Perfusion: Near-automated Evaluation from Contrast-enhanced MR Images Obtained at Rest and during Vasodilator Stress

PURPOSE To develop and validate a technique for near-automated definition of myocardial regions of interest suitable for perfusion evaluation during vasodilator stress cardiac magnetic resonance (MR) imaging. MATERIALS AND METHODS The institutional review board approved the study protocol, and all patients provided informed consent. Image noise density distribution was used as a basis for endocardial and epicardial border detection combined with nonrigid registration. This method was tested in 42 patients undergoing contrast material-enhanced cardiac MR imaging (at 1.5 T) at rest and during vasodilator (adenosine or regadenoson) stress, including 15 subjects with normal myocardial perfusion and 27 patients referred for coronary angiography. Contrast enhancement-time curves were near-automatically generated and were used to calculate perfusion indexes. The results were compared with results of conventional manual analysis, using quantitative coronary angiography results as a reference for stenosis greater than 50%. Statistical analyses included the Student t test, linear regression, Bland-Altman analysis, and κ statistics. RESULTS Analysis of one sequence required less than 1 minute and resulted in high-quality contrast enhancement curves both at rest and stress (mean signal-to-noise ratios, 17±7 [standard deviation] and 22±8, respectively), showing expected patterns of first-pass perfusion. Perfusion indexes accurately depicted stress-induced hyperemia (increased upslope, from 6.7 sec(-1)±2.3 to 15.6 sec(-1)±5.9; P<.0001). Measured segmental pixel intensities correlated highly with results of manual analysis (r=0.95). The derived perfusion indexes also correlated highly with (r up to 0.94) and showed the same diagnostic accuracy as manual analysis (area under the receiver operating characteristic curve, up to 0.72 vs 0.73). CONCLUSION Despite the dynamic nature of contrast-enhanced image sequences and respiratory motion, fast near-automated detection of myocardial segments and accurate quantification of tissue contrast is feasible at rest and during vasodilator stress. This technique, shown to be as accurate as conventional manual analysis, allows detection of stress-induced perfusion abnormalities.

Volumetric quantification of myocardial perfusion using analysis of multi-detector computed tomography 3D datasets: comparison with nuclear perfusion imaging

BackgroundAlthough the ability of multi-detector computed tomography (MDCT) to detect perfusion abnormalities associated with acute and chronic myocardial infarction (MI) has been demonstrated, this methodology is based on visual interpretation of selected 2D slices.ObjectivesWe sought to develop a new technique for quantitative volumetric analysis of myocardial perfusion from 3D datasets and test it against resting nuclear myocardial perfusion imaging (NMPI) reference.MethodsWe studied 44 patients undergoing CTCA: a control group of 15 patients and a study group of 29 patients. MDCT datasets acquired for CTCA were analyzed using custom software designed to: (1) generate bull’s eye display of myocardial perfusion and (2) calculate a quantitative index of extent and severity of perfusion abnormality, QH, for 16 volumetric myocardial segments. Visual interpretation of MDCT-derived bull’s eyes was compared with rest NMPI scores using kappa statistics of agreement on a coronary territory and patient basis. Quantitative MDCT perfusion data were correlated with rest NMPI summed scores and used for objective detection of perfusion defects.ResultsVisual analysis of MDCT-derived bull’s eyes accurately detected perfusion defects in agreement with NMPI (kappa = 0.70 by territory; 0.79 by patient). Quantitative data were in good agreement with NMPI, as reflected by: (1) correlation of 0.87 (territory) and 0.84 (patient) between summed QH and NMPI scores, (2) area under ROC curve 0.87 with sensitivity of 0.79–0.92, specificity 0.83–0.91, and accuracy 0.83–0.89 for objective detection of abnormalities.ConclusionsOur new technique for volumetric analysis of 3D MDCT images allows accurate objective detection of perfusion defects. This perfusion information can be obtained without additional radiation or contrast load, and may aid in elucidating the significance of coronary lesions.

Quantification of mitral annulus dynamic morphology in patients with mitral valve prolapse undergoing repair and annuloplasty during a 6-month follow-up

AIMS Mitral valve (MV) repair is the preferred treatment for mitral regurgitation associated with organic MV prolapse (MVP). Our goals were to describe by transthoracic real-time 3D echocardiography (RT3D TTE) the pre-operative changes in mitral annulus (MA) dynamic morphology related to MVP, compared with a normal population, and to evaluate the differential long-term effects induced by annuloplasty, using either an incomplete flexible band or a complete semi-rigid ring. METHODS AND RESULTS Forty-four patients (62 ± 11 years) with organic MVP and ejection fraction >55% were studied by RT3D TTE the day before MV repair, and 3 and 6 months after (23 patients received a complete rigid ring-CAR, 21 an incomplete flexible band-COS). An age-matched group of 20 normal subjects (57 ± 9 years) was studied as control. After initialization, the MA was tracked frame-by-frame in 3D, and several parameters computed. Differences in MVP vs. controls, vs. pre-surgery, and between rings were tested (P < 0.05). MVP showed enlarged MA resulting in greater area and height during the cardiac cycle, with reduced planarity compared with controls. Annuloplasty resulted in reduced MA area in both CAR and COS, with minimal area change, and planar shape (more evident in CAR than COS). CONCLUSION The main factor affecting MA function after annuloplasty appears to be the undersizing of the MA dimensions, and not the choice of the ring. This methodology could represent the basis for further evaluation of implanted rings, to provide the surgeon with additional information to be used in the pre-surgical planning and ring selection.

Automated frame-by-frame endocardial border detection from cardiac magnetic resonance images for quantitative assessment of left ventricular function: Validation and clinical feasibility

To develop a technique based on image noise distribution for automated endocardial border detection from cardiac magnetic resonance (CMR) images throughout the cardiac cycle, validate it, and test its clinical utility.

Mitral Valve Dynamics in Severe Aortic Stenosis before and after Aortic Valve Replacement

BACKGROUND The aortic and mitral valves are anatomically linked through a fibrous continuity. The investigators hypothesized that severe aortic stenosis (AS) would alter this fibrous continuity, affecting both the mitral valve and left ventricular function, and that mitral valve function would be altered after aortic valve replacement (AVR). The aim of this study was to evaluate the impact of AS and its treatment with surgical AVR on the mitral valve. METHODS Three-dimensional transesophageal echocardiography (using a Philips iE33 system) was performed on 49 patients: 20 controls with normal valves and left ventricular function, 20 with AS and normal left ventricular function studied before and after AVR, and nine with systolic heart failure and normal valves. Custom software tracked the aortic and mitral valves in three-dimensional space, allowing automated measurements of aortic and mitral annular (MA) morphology throughout the cardiac cycle. RESULTS Patients with AS before AVR had reduced MA velocities. After AVR, aortic and MA areas were significantly smaller throughout the cardiac cycle compared with controls and pre-AVR values. MA displacement was reduced after AVR and in patients with systolic heart failure compared with those with AS and controls. CONCLUSIONS Dynamic MA function is changed with AS and after AVR through alterations in the aortic-mitral fibrous continuity. The prosthetic valve ring results in reduced aortic and MA areas, which could affect blood flow in and out of the left ventricle. These changes suggest that the design of future prosthetic aortic valves should be more flexible to preserve the function of the aortic-mitral fibrous continuity.

3D printing of normal and pathologic tricuspid valves from transthoracic 3D echocardiography data sets

Aims To explore the feasibility of using transthoracic 3D echocardiography (3DTTE) data to generate 3D patient-specific models of tricuspid valve (TV). Methods and Results Multi-beat 3D data sets of the TV (32 vol/s) were acquired in five subjects with various TV morphologies from the apical approach and analysed offline with custom-made software. Coordinates representing the annulus and the leaflets were imported into MeshLab (Visual Computing Lab ISTICNR) to develop solid models to be converted to stereolithographic file format and 3D print. Measurements of the TV annulus antero-posterior (AP) and medio-lateral (ML) diameters, perimeter (P), and TV tenting height (H) and volume (V) obtained from the 3D echo data set were compared with those performed on the 3D models using a caliper, a syringe and a millimeter tape. Antero-posterior (4.2 ± 0.2 cm vs. 4.2 ± 0 cm), ML (3.7 ± 0.2 cm vs. 3.6 ± 0.1 cm), P (12.6 ± 0.2 cm vs. 12.7 ± 0.1 cm), H (11.2 ± 2.1 mm vs. 10.8 ± 2.1 mm) and V (3.0 ± 0.6 ml vs. 2.8 ± 1.4 ml) were similar (P = NS for all) when measured on the 3D data set and the printed model. The two sets of measurements were highly correlated (r = 0.991). The mean absolute error (2D − 3D) for AP, ML, P and tenting H was 0.7 ± 0.3 mm, indicating accuracy of the 3D model of <1 mm. Conclusion Three-dimensional printing of the TV from 3DTTE data is feasible with highly conserved fidelity. This technique has the potential for rapid integration into clinical practice to assist with decision-making, surgical planning, and teaching.