3D TEE Research Articles

The Key Role of 3D TEE in Assessing the Morphology of Degenerative Mitral Valve Regurgitation

Two-dimensional transthoracic echocardiography (2D TTE) and two-dimensional transesophageal echocardiography (2D TEE) are regarded as the main imaging techniques for the assessment of degenerative mitral valve regurgitation (DMVR). However, describing the complex morphology of DMVR with 2D TTE and 2D TEE remains at the very least challenging. Three-dimensional (3D) TEE is an ideal technique for illustrating the extremely variable morphology of DMVR, providing images of unparalleled quality in terms of anatomical detail. In this review, we describe the key role of 3D TEE in various morphological scenarios that reflect everyday experiences in an echocardiographic laboratory. We also discuss the growing role of 3D TEE in mitral valve (MV) transcatheter edge-to-edge repair (TEER) and new modalities such as photorealistic and transparent displays, surface rendering parametric color maps, new algorithms for MVR quantification, and the potential role of new mini-TEE probes in adult patients with DMVR.

TCT-81 Accuracy of 3D TEE Compared to CT for Sizing of the Tricuspid Annulus

TCT-81 Accuracy of 3D TEE Compared to CT for Sizing of the Tricuspid Annulus

Feasibility of Using 3D TEE for TMVR Pre-Screening

Feasibility of Using 3D TEE for TMVR Pre-Screening

Impact of 3D TEE guided ASD transcatheter closure on procedure outcome and radiation exposure

Abstract Background Transcatheter ASD device closure of secondum ASD is widely accepted in closure of ASD. Radiation exposure increases the risk of cancer for both patients and staff members, fusion of 3- D TEE and fluoroscopy has helped us decrease radiation exposure during whole procedure. Aim to assess feasibility of 3 D TEE guidance in transcatheter ASD closure and assess its value in reducing radiation exposure as compared to control patients. Methods This study was conducted on 30 patients with secundum ASD referred to cardiology department - Ain Shams University for percutaneous ASD device closure under 3D TEE guidance and 54 control patients who performed percutaneous ASD device closure using conventional method. we calculated total procedure time (min), total DAP (mGy/cm2), (FT) fluoroscopy time (min), total air kerma (mGy), maximum ASD diameter (mm) and we recorded implanted device size and device type for all the patients. Results There was no significant difference between both groups regarding FT, total air kerma, dose area product. Operative time of study group was significantly longer than control group although FT reduced significantly in last case of the study. In the last 10 cases of the study radiation exposure decreases and was significantly lower than control group. Conclusion The Use of 3 D-TEE by well-trained imaging cardiologist on tracking catheter during percutaneous ASD device closure decrease significantly radiation exposure of patients as well as medical personnel.

Two-dimensional transthoracic measure of mitral annulus in mitral valve prolapse and moderate to severe regurgitation: a method comparison analysis with three-dimensional transesophageal echocardiography

BackgroundMitral annulus (MA) area is derived during transthoracic echocardiography (TTE) assuming of a circular shape using the MA diameter from the apical 4 chamber (A4c) view. Since the MA is not a circular structure, we hypothesized that an elliptical model using parasternal long-axis (PLAX) and apical 2 chamber (A2c) view measured MA diameters would have better agreement with 3-dimensional transesophageal echocardiography (3D TEE) measured MA in degenerative mitral valve disease (DMVD).MethodsSeventy-six patients with moderate-to-severe DMVD had 2D TTE and 3D TEE performed. MA area was measured retrospectively using semi-automatic modeling of 3D data (3D TEEsa) and considered as the reference method. MA diameters were measured using different 2D TTE views. MA area was calculated using assumptions of a circular or an elliptical shape. 2D TTE derived and 3D TEEsa. MA areas were compared using linear regression and Bland-Altman analysis.ResultsThe median MA area measured at 3D TEEsa was 1,386 (1,293–1,673) mm2. With 2D TTE, the circular model using A4c view diameter resulted in a small systematic underestimation of MA area (6%), while the elliptical model using PLAX and A2c diameters resulted in 25% systematic underestimation. The standard deviations of the distributions of inter-method differences were wide for all 2D TTE methods (265–289 mm2) when compared to 3D TEEsa, indicating imprecision.ConclusionsWhen compared with 3D TEEsa modeling of the MA as the reference, the assumption of a circular shape using A4c TTE view diameter was the method with the least systematic error to assess MA area in DMVD and moderate to severe regurgitation.

Three‐dimensional transesophageal echocardiography measurements of ASD sizing parameters in comparison to balloon sizing method in percutaneous ASD closure

AbstractBackgroundBalloon sizing (BS) has been used for device size selection in percutaneous atrial septal defect (ASD) closure. Due to its limitations, alternative imaging techniques like three‐dimensional transesophageal echocardiography (3D‐TEE) are valuable for guiding ASD device size selection during ASD closure procedures. The purpose of this study was to compare ASD sizing using measurements obtained from 3D–TEE to those utilizing the standard balloon sizing method.MethodsWe identified 53 patients with single secundum type ASD without PFO who underwent percutaneous closure at the Tehran Heart Center between 2019 and 2022. Balloon sizing was performed in all patients with the stop‐flow technique, and the choice of device size was determined based on the sizing derived from BS. 3D‐TEE imaging was performed before the intervention, and the ASD shape and quality of ASD rims were assessed.ResultsAmong the 53 patients who underwent single ASD device closure, multiple 3D TEE measurements significantly correlated with balloon sizing results. This included defect area, perimeter, and diameter obtained from 3D‐TEE images multi‐planar reconstruction. ASD perimeter detected by 3D TEE had the best correlation with BS results. When divided by the shape of ASD, there was no significant difference between our 3D‐images data and BS in round or oval‐shaped ASDs.ConclusionThe 3D‐TEE study is reliable for assessing ASD configurational characteristics in percutaneous device closure candidates. 3D‐TEE has the potential to accurately determine the appropriate device size and reduce complications, costs, and procedural duration. Further research is needed to validate these findings and establish the role of 3D‐TEE measurements in guiding the best treatment decisions for ASD closure.

Misidentification of the True Aortic Annulus With 2-dimensional Echocardiography: A Critical Appraisal Using 3-Dimensional Imaging

ObjectivesThis study aimed to evaluate the accuracy of identifying the 'true aortic valve (AV) annulus' using 2-dimensional (2D) echocardiography with the aim of highlighting potential misidentification issues in clinical practice. DesignAn observational study employing 3-dimensional (3D) datasets to generate 2D images of the AV annulus for analysis. SettingThe study was conducted in an academic medical center. ParticipantsThree-dimensional transesophageal echocardiography (3D TEE) datasets were obtained from 11 patients with normal AV and aortic root anatomies, undergoing coronary artery bypass surgery. Attending anaesthesiologists certified by the national board of echocardiography (NBE) were subsequently approached to participate in this study. InterventionsTwo images per patient were generated from 3D datasets, reflecting the mid-esophageal long-axis view of the AV: a 'True AV Annulus Image' and an 'Off-Axis Image'. A survey was distributed to NBE certified perioperative echocardiographers across 12 academic institutions to identify the 'true AV annulus' from these images. Measurements and Main ResultsThe survey, completed by 45 qualified respondents, revealed a significant misidentification rate of the 'true AV annulus', with only 36.8% of responses correctly identifying it. The rate of correct identification varied across image sets, with 44.4% of participants unable to correctly identify any 'true AV annulus' image. ConclusionsThe study highlights the limitations of 2D echocardiography in accurately identifying the 'true AV annulus' in complex 3D structures like the aortic root. The findings suggest a need for greater reliance on advanced imaging modalities, such as 3D echocardiography, to improve accuracy in clinical practice.

Intraoperative and Intraprocedural Use of 3-Dimensional Transesophageal Echocardiography: An International European Association of Cardiothoracic Anesthesia and Intensive Care Survey of Cardiac Surgical Centers

ObjectiveTo assess the intraoperative use of three-dimensional transesophageal echocardiography (3D TEE) in cardiac surgical centers, we created a survey aimed at evaluating the availability of equipment, the use of 3D TEE for specific surgical and interventional procedures and single image modalities. Finally, we asked to identify the perceived impact on patient's management and current limitations to its routine use. DesignMultiple-choice 25-questions online survey submitted to the members of the European Association of Cardiothoracic Anesthesia and Intensive Care (EACTAIC) on December 6th, 2021 and closed on January 31st, 2022. SettingOnline survey. ParticipantsRegistered EACTAIC members in 2021. InterventionsNone. Measurements and Main ResultsA total of 239 respondents from 44 different countries took part in the survey (27% of total 903 EACTAIC members). Most respondents (59%) were TEE certified by National Board of Echocardiography (NBE), European Association of Cardiovascular Imaging (EACVI/EACTAIC) or had a national certificate. Sixty-eight percent of respondents had no formal 3D TEE training. Eight percent of respondents had no 3D machines. While 40% had one for each operating room, 33% had only one for the entire operating room block. 3D TEE was performed most frequently in more than 67% of cases for mitral valve (MV) surgery and in more than 54% of cases for mitral- and tricuspid clips, aortic valve- (AV), tricuspid valve- (TV) and aortic surgery. ConclusionCurrent guidelines suggest integrating 3D TEE in all comprehensive examinations. Our survey reports that intraoperative 3D TEE was used in the majority of mitral valve surgery and only half of other valve surgeries and transcatheter procedures. Its use may be explained by the availability of 3D machines, trained personnel and limited time to perform TEE in the operating room. Educational initiatives for training in 3D TEE may further increase its routine use.

Impact of stroke volume assessment by three-dimensional transesophageal echocardiography on the classification of low-gradient aortic stenosis.

Accurate assessment of flow status is crucial in low-gradient aortic stenosis (AS). However, the clinical implication of three-dimensional transesophageal echocardiography (3DTEE) on flow status evaluation remains unclear. This study aimed to investigate the assessment of flow status using 3D TEE in low-gradient AS patients. We retrospectively reviewed patients diagnosed with low-gradient AS and preserved ejection fraction at our institution between 2019 and 2022. Patients were categorized into low-flow/low-gradient (LF-LG) AS or normal-flow/low-gradient (NF-LG) AS based on two-dimensional transthoracic echocardiography (2DTTE). We compared the left ventricular outflow tract (LVOT) geometry between the two groups and reclassified them using stroke volume index (SVi) obtained by 3DTEE. Among 173 patients (105 with LF-LG AS and 68 with NF-LG AS), 54 propensity-matched pairs of patients were analyzed. 3DTEE-derived ellipticity index of LVOT was significantly higher in LF-LG AS patients compared to NF-LG AS patients (p = 0.012). We assessed the discordance in flow status classification between SVi2DTTE and SVi3DTEE in both groups using a cutoff value of 35ml/m2. The LF-LG AS group exhibited a significantly higher discordance rate compared to the NF-LG AS group, with rates of 50% and 2%, respectively. The optimal cutoff values of SVi3DTEE for identifying low flow status, based on 2DTTE-derived cutoff values, were determined to be 43ml/m2. LVOT ellipticity in low-gradient AS patients varies depending on flow status, and this difference contributes to discrepancies between SVi3DTEE and SVi2DTTE, particularly in LF-LG AS patients. Utilizing SVi3DTEE is valuable for accurately assessing flow status.

Rare complications of infective endocarditis in marfan-like morphotype: diagnosis of multiple mitral valve aneurysms and aortic root abscess using three-dimensional transesophageal echocardiography

Mitral valve aneurysm (MVA) is characterized by a saccular outpouching of the mitral leaflet, and it represents a rare condition typically associated with aortic valve endocarditis. Three-Dimensional Transesophageal Echocardiography (3D-TEE) serves as an effective tool for detecting the presence of MVA and its potential complications. In this report, we present a case involving a young man with striking images of bicuspid aortic valve endocarditis complicated by an aortic root abscess and multiple perforated mitral valve aneurysms, diagnosed using 3D TEE. This case suggests the uncommon coexistence of Marfan like morphotype, bicuspid aortic valve, and infective endocarditis as a triple mechanism in the occurrence of MVA. It underscores the significance of early and accurate imaging diagnosis for facilitating prompt surgical intervention.

Remodeling on Lateral Side of Posterior Mitral Leaflet in Recurrent Mitral Regurgitation after Mitral Annuloplasty for Patients with Atrial Functional Mitral Regurgitation

Objective. The high recurrence rate of mitral regurgitation (MR) in patients with atrial functional mitral regurgitation (AFMR) who underwent mitral annuloplasty (MAP) is reported. However, the mechanism of recurrence is not fully understood and appropriate surgical intervention remains unknown. Herein, we reviewed patients with AFMR who underwent MAP at our institution and investigated the preoperative geometric characteristics of the mitral valve in terms of MR recurrence after surgery. Methods. We retrospectively evaluated 20 patients with AFMR who underwent MAP between 2010 and 2022. The mean follow-up period was 3.2 ± 2.3 years. Preoperative three-dimensional transesophageal echocardiography (3D TEE) was available for all patients, and geometric analysis of the mitral valve was performed using the Philips Q-Lab software. Results. MR recurred in six patients. The rates of freedom from MR recurrence were 79% and 57% at one and three years, respectively. The lateral portion of the posterior mitral leaflet (PML) in patients with recurrent MR was longer and thicker than that in patients without recurrent MR (length of P1; 10 ± 3 vs. 15 ± 5 mm, p<0.01, length of P2; 11 ± 4 vs. 14 ± 4 mm, p=0.23, length of P3; 8 ± 3 vs. 10 ± 3 mm, p=0.13). Conclusions. Patients with remodeling of the lateral portion of PML tended to have recurrent MR after MAP. This factor could indicate progressive remodeling, and MAP alone may not be a sufficient intervention for these patients.

New method for quantification of atrial septum defect shunting by echocardiography

Abstract Background Atrial septum defect (ASD) is a common congenital heart disease. Echocardiography is the preferred method for detection and characterization of ASD. Accurate quantification of shunting is pivotal, but often requires right heart catheterization (RHC). In the present study, we introduce a new non-invasive method for accurate quantification of the ASD shunt by combined transesophageal- (TEE) and transthoracic (TTE) echocardiography. Shunt by RHC was used as a reference method. Method In 22 adults with secundum ASD, left ventricular (LV) stroke volume (SV) was measured by the pulsed Doppler method using 2D TTE. The shunt volume passing through the ASD was quantified as the ASD area measured by planimetry from 3D TEE, multiplied with the time velocity integral (TVI) of the PW Doppler obtained at the center of the ASD by TEE. Finally, the ratio of the pulmonary to systemic shunt (Qp:Qs) was calculated as (LVSV+ASDvolume)/LVSV. Shunt by RHC was assessed by the Fick’s principle. Results Mean shunt was 2.2±0.7 (±SD) by echocardiography and 2.1±0.7 by RHC, with a mean difference of -0.1±0.4 (Figure 1). The correlation between shunt measured by RHC and echocardiography was strong (r=0.86, p<0.0001; Figure 2). Conclusion The present study demonstrates that ASD shunting can be quantified accurately by combining TTE and TEE, suggesting a new non-invasive approach in settings where RHC is not feasible or available.Figures

Abstract 15629: Innovative Approach to Mitral Regurgitation in a Patient With Partially Dehisced Annuloplasty Band After Mitral Valve Repair

Case: A 65-year-old patient presented 4 months after mitral valve repair (annuloplasty band, commissuroplasty, neo-chordae to the anterior mitral leaflet (AL)). At follow up, he developed significant hemolytic anemia (Hemoglobin 10.1g/dL, LDH 650U/L, Bilirubin 1.4mg/dL and haptoglobin<14 mg/dL). TEE revealed the substrate for hemolysis: moderate-severe mitral regurgitation (MR) starting at the coaptation of A2 and P2 scallops due to AL overriding the posterior (PL). The jet was then directed posteriorly to a small (3 x 6 mm confirmed by cardiac CT) area of annuloplasty band dehiscence at the base of the P2 scallop, with the band in direct path of the flow. The unique feature was that AL retained coaptation with the annuloplasty band, thus forming a small tunnel from the A2-P2 coaptation defect to the dehisced area. Given that redo surgery early after initial intervention would be challenging, the Heart Team decided to pursue percutaneous closure at the level of the dehisced annuloplasty to reduce regurgitation and mitigate hemolysis. Under 3D TEE guidance closure with a 12mm AVP plug was attempted but resulted in interference with PL motion with a new jet of regurgitation laterally. Using two 8mm AVP plugs was successful in closing the dehiscence with minimal impact on PL. Overall regurgitation was reduced to mild. Within a week hemolysis labs improved: LDH337 U/L, Bilirubin0.7 mg/dL. Discussion: Annuloplasty band dehiscence is a known cause of recurrent MR after repair. As regurgitation occurs at the leaflet coaptation zone, percutaneous closure of these defects is usually futile. In this patient we took advantage of the maintained coaptation between the AL and annuloplasty band.

Assessment of Atrial Septal Defects through Advanced Three-Dimensional Transesophageal Echocardiography Imaging

This article presents a study on the use of three-dimensional transesophageal echocardiography (3D TEE) in the evaluation of atrial septal defects (ASD) in adults. With 3D TEE, a more accurate anatomical assessment of the atrial septum is achieved, allowing precise measurement of size, shape, and border characteristics of the ASD. In a series of 27 cases, the 3D evaluation showed a strong correlation between measured parameters and the size of the closure device required. 3D TEE appears to be a significant advancement in cardiovascular imaging, enhancing pre-interventional assessment and the success of interventions for ostium secundum ASD.

Study of mitral valve remodling in patients with atrial functional mitral valve regurgitation using three-dimensional echocardiography

Abstract Background The global burden of atrial fibrillation (AF) is enormous for healthcare systems. AF is typically classified into five distinct patterns depending on the onset, progression, and resolution of AF episodes, first diagnosed AF, paroxysmal AF, persistent AF, long-standing persistent AF& permanent AF. Atrial structural remodeling or exacerbation of atrial cardiomyopathy are generally defining features of the transition from paroxysmal to non-paroxysmal AF. The duration of rhythm monitoring and the presence of a substrate are both important factors in determining the rate of AF development. In the existence of a structurally normal valve, functional MR develops when there is a mismatch between the tethering forces exerted by the heart & the closing forces exerted by the heart. In the context of functional MR annular dilation alone, can constitute a separate etiology of MR (atrial functional MR). TEE provides supplementary imaging, particularly if TTE windows are technically challenging, making it a useful tool even if TTE is the primary technique for assessing and quantifying mitral valve disease. 3DE data sets can be acquired from either TTE or TEE approach, allowing real-time visualization of the cardiac structures, it is superior to 2DE in quantification of cardiac chamber volumes and function, assessment of the mechanisms and severity of heart valve diseases, evaluation of cardiac complex anatomy. Aim of the work To study mitral valve apparatus remodeling in patients with atrial functional mitral valve regurgitation using three-dimensional echocardiography. Methods This study included a total of 30 patients with diagnosis of atrial fibrillation divided in to two groups, 15 patients having no/ mild mitral regurgitation while 15 patients having moderate/severe mitral regurgitation, they were subjected to 2D and 3D TEE echocardiographic assessment of MR degree, LA volumes, mitral leaflets and mitral annulus parameters. Results There was statistically significant difference between the two groups as regard the posterior leaflet area as larger area was estimated in (Mod/severe MR) group compared to (No/ mild MR) group, with mean posterior leaflet area in group I was (8.96 ± 2.60) and (7.30 ± 2.17) in group II with (P value = 0.029) as well as there was statistically significant difference between the two groups as regard total leaflet area/Mitral annular area ratio as smaller ratio was estimated in (Mod/severe MR) group as compared to (No/mild MR) group, with the mean total leaflet area /mitral annular area ratio in group I was (1.22 ± 0.04) and (1.26 ± 0.04) in group II with (P value = 0.008). Conclusion Isolated annular dilatation can cause significant functional atrial mitral regurgitation while mitral leaflet area increases in AF as the annulus dilates, but this adaptation may plateau at larger annular areas, with the resulting leaflet deficiency causing functional atrial mitral regurgitation. Additional Content An author video to accompany this abstract is available on https://academic.oup.com/eurheartjsupp. Please click on the arrow next to ‘More Content’ and then click on ‘Author videos’.

Contribution of Three-Dimensional Transesophageal Echocardiography in the Assessment of Atrial Septal Defects (ASD)

The article examines the contribution of real-time three-dimensional transesophageal echocardiography (3D TEE) in the assessment of ostium secundum atrial septal defects (ASD) in adults. 3D TEE provides a precise and comprehensive view of cardiac anatomy, enabling the evaluation of size, shape, and border quality of the ASD. In a series of 27 cases, 3D TEE demonstrated a strong correlation between 3D-measured ASD parameters and the size of the closure device required. This technique is crucial for accurate pre-interventional evaluation, enhancing the success and safety of percutaneous or surgical interventions for ostium secundum ASD. Three-dimensional transesophageal echocardiography represents a significant advancement in cardiovascular imaging for complex structural heart abnormalities.

P271 CASEOUS CALCIFICATION OF THE MITRAL ANNULUS: ROLE OF 3D ECHOCARDIOGRAPHY

Abstract The caseous calcification of the mitral annulus (CCMA) is a rare degenerative condition of the mitral valve (0.067% prevalence in the general population) that generally affects older women with hypertension, chronic kidney disease and dyslipidemia. Usually CCMA is asymptomatic and it is associated with mild to moderate mitral regurgitation and it can cause severe mitral valve dysfunction that requires surgical treatment. CASE 1: A 84–year–old woman, with arterial hypertension, was evaluated in our clinic to perform a transthoracic echocardiogram (TTE) for a previous finding of heart murmur. TTE reveled at the level of the posterior mitral annulus a hyperechoic roundish formation with a central eco–shiny area with a maximum diameter of 20x20 mm. A tridimensional trans–esophageal echocardiography (3D TEE) allowed a better characterization of the mass showing well–defined contours, adhered to the posterior mitral annulus, systolic dislocation of the anterior mitral leaflet, with slight mitral regurgitation. Considering the morphological characteristics of the mass we concluded for a presumptive diagnosis of CMAC. We recommended regular follow–up to the patient. After 6 and 12 months the mass did not change in size and echostructure. CASE 2: An 88–year–old woman with chronic kidney disease, high blood pressure and chronic ischemic heart disease was admitted to our ward for acute heart failure. TTE showed a large an echodense mass (43 × 19 mm) involving the posterior mitral annulus, with a central echo–lucent area. A 3D TEE was performed with better mass characterization: involvement of the entire posterior mitral ring, reduced movement of the posterior mitral flap, anterior mitral flap with normal morphology and normal mobility. In consideration of the echocardiographic characteristics we concluded for the presence of CMAC. We discharged the patient with indication for a regular clinical and echocardiographic follow–up. Conclusions The 3D TTE provides adequate morphostructural information that allows in most cases to characterize the CCAM. When the transthoracic approach is difficult due to poor acoustic windows, 3D TEE can be used. Only in rare cases it is necessary to use second–level diagnostic tests such as CT and Cardiac Magnetic Resonance Imaging.

Tricuspid valve endocarditis: 3D TEE En face view helps better identification of location and extent of involvement\.

Tricuspid valve endocarditis: 3D TEE En face view helps better identification of location and extent of involvement\.

Three-dimensional transesophageal echocardiographic evaluation of aortic plaque after cerebrovascular event

Introduction and objectivesTransesophageal echocardiography (TEE) is crucial in order to assess aortic anatomy after stroke. Although routinely used to assess cardiovascular anatomy and function, three-dimensional echocardiography (3D TEE) is less used for aortic evaluation. We thus sought to assess prospectively whether additional information on aortic plaque morphology could be obtained with 3D TEE after an ischemic stroke. MethodsPatients within one week of a stroke (confirmed by brain computed tomography/magnetic resonance) underwent TEE and 3D findings were compared with two-dimensional (2D) (aorta plaque number, dimensions, area and the presence of debris and ulcerations). Patients were followed for two years for death or a new stroke. ResultsWe assessed 78 patients, 43 (55%) male, aged 62±14 years old, 92% in sinus rhythm. Aortic atheroma was found mainly in the descending aorta (50%); plaque thickness was similar for 2D TEE (0.29±0.03 cm) and 3D TEE (0.29±0.04 cm), whereas plaque area was slightly increased for 3D measurements (0.24±0.02 cm2 versus 0.37±0.03 cm2 respectively, p<0.05), with a strong correlation found both for aortic plaque thickness (r=0.91) and area (r=0.80) measurements. While aortic debris were equally seen with both techniques, 3D TEE defines the presence of ulcerations (six ulcerations unseen with 2D TEE better, p=0.03). There were 11 events (six deaths and five new strokes) during follow-up, unrelated to plaque characteristics. ConclusionTo evaluate aortic plaque morphology, 3D TEE is superior to 2D TEE due to improved detection of ulcerated aortic plaque; this might provide additional information in patients after ischemic stroke.

Complete region of interest reconstruction by fusing multiview deformable three-dimensional transesophageal echocardiography images.

While three-dimensional transesophageal echocardiography (3D TEE) has been increasingly used for assessing cardiac anatomy and function, it still suffers from a limited field of view (FoV) of the ultrasound transducer. Therefore, it is difficult to examine a complete region of interest without moving the transducer. Existing methods extend the FoV of 3D TEE images by mosaicing multiview static images, which requires synchronization between 3D TEE images and electrocardiogram (ECG) signal to avoid deformations in the images and can only get the widened image at a specificphase. This work aims to develop a novel multiview nonrigid registration and fusion method to extend the FoV of 3D TEE images at different cardiac phases, avoiding the bias toward the specifically chosenphase. A multiview nonrigid registration and fusion method is proposed to enlarge the FoV of 3D TEE images by fusing dynamic images captured from different viewpoints sequentially. The deformation field for registering images is defined by a collection of affine transformations organized in a graph structure and is estimated by a direct (intensity-based) method. The accuracy of the proposed method is evaluated by comparing it with two B-spline-based methods, two Demons-based methods, and one learning-based method VoxelMorph. Twenty-nine sequences of in vivo 3D TEE images captured from four patients are used for the comparative experiments. Four performance metrics including checkerboard volumes, signed distance, mean absolute distance (MAD), and Dice similarity coefficient (DSC) are used jointly to evaluate the accuracy of the results. Additionally, paired t-tests are performed to examine the significance of theresults. The qualitative results show that the proposed method can align images more accurately and obtain the fused images with higher quality than the other five methods. Additionally, in the evaluation of the segmented left atrium (LA) walls for the pairwise registration and sequential fusion experiments, the proposed method achieves the MAD of (0.07 ± 0.03) mm for pairwise registration and (0.19 ± 0.02) mm for sequential fusion. Paired t-tests indicate that the results obtained from the proposed method are more accurate than those obtained by the state-of-the-art VoxelMorph and the diffeomorphic Demons methods at the significance level of 0.05. In the evaluation of left ventricle (LV) segmentations for the sequential fusion experiments, the proposed method achieves a DSC of (0.88 ± 0.08), which is also significantly better than diffeomorphic Demons at the 0.05 level. The FoVs of the final fused 3D TEE images obtained by our method are enlarged around two times compared with the originalimages. Without selecting the static (ECG-gated) images from the same cardiac phase, this work addressed the problem of limited FoV of 3D TEE images in the deformable scenario, obtaining the fused images with high accuracy and good quality. The proposed method could provide an alternative to the conventional fusion methods that are biased toward the specifically chosenphase.