Three-dimensional (3D) echocardiographic analysis of congenital heart disease in the fetus: comparison with cross-sectional (2D) fetal echocardiography.

OBJECTIVE: We attempted to assess the ability of Doppler-gated three-dimensional (3D) fetal echocardiography to reconstruct and display specific cardiac structures in fetuses with cardiac anomalies and to determine whether any advantage is offered by 3D sonographic cardiac examination over conventional fetal echocardiography. DESIGN: After 2D fetal echocardiographic examination, 3D cardiac data were collected prospectively in 22 fetuses with various congenital heart defects. Their ages ranged from 19 to 35 weeks' gestation. Basic echocardiographic key views of the venoatrial, atrioventricular and ventriculoarterial connections were derived from volume data sets and selected for 3D reconstruction and analysis. Comparisons were made with 2D echocardiographic imaging of the fetal hearts and the diagnostic image quality of visualized structural details was evaluated. RESULTS: The underlying cardiac malformation was well or satisfactorily visualized in 20 fetuses using 2D imaging. Gated 3D volume data sets enabled diagnostically acceptable visualization of all affected cardiac structures in 7 of 22 fetuses. High-quality 3D reconstruction of the site and spatial orientation of ventricular septal defects was obtained in 9 of 13 patients. Two-dimensional imaging remained the principal diagnostic modality in all cases with additional structural detail being obtained by 3D imaging in only two fetuses. CONCLUSIONS: Three-dimensional imaging of fetal heart disease is feasible for a wide range of lesions, and may provide additional information of clinical value in a small number of cases when compared with 2D imaging.     

Real-time 3-dimensional fetal echocardiography with an instantaneous volume-rendered display: early description and pictorial essay.

OBJECTIVE: Random fetal motion, rapid fetal heart rates, and cumbersome processing algorithms have limited reconstructive approaches to 3-dimensional fetal cardiac imaging. Given the recent development of real-time, instantaneous volume-rendered sonographic displays of volume data, we sought to apply this technology to fetal cardiac imaging. METHODS: We obtained 1 to 6 volume data sets on each of 30 fetal hearts referred for formal fetal echocardiography. Each volume data set was acquired over 2 to 8 seconds and stored on the system's hard drive. Rendered images were subsequently processed to optimize translucency, smoothing, and orientation and cropped to reveal "surgeon's eye views" of clinically relevant anatomic structures. Qualitative comparison was made with conventional fetal echocardiography for each subject. RESULTS: Volume-rendered displays identified all major abnormalities but failed to identify small ventricular septal defects in 2 patients. Important planes and views not visualized during the actual scans were generated with minimal processing of rendered image displays. Volume-rendered displays tended to have slightly inferior image quality compared with conventional 2-dimensional images. CONCLUSIONS: Real-time 3-dimensional echocardiography with instantaneous volume-rendered displays of the fetal heart represents a new approach to fetal cardiac imaging with tremendous clinical potential.     

Myocardial Fiber Mapping of Rat Hearts,Using Apparent Backscatter,with Histologic Validation

Myocardial fiber architecture is a physiologically important regulator of ejection fraction, strain and pressure development. Apparent ultrasonic backscatter has been shown to be a useful method for recreating the myocardial fiber architecture in human-sized sheep hearts because of the dependence of its amplitude on the relative orientation of a myofiber to the angle of ultrasonic insonification. Thus, the anisotropy of the backscatter signal is linked to and provides information about the fiber orientation. In this study, we sought to determine whether apparent backscatter could be used to measure myofiber orientation in rodent hearts. Fixed adult-rat hearts were imaged intact, and both a transmural cylindrical core and transmural wedge of the left ventricular free wall were imaged. Cylindrical core samples confirmed that backscatter anisotropy could be measured in rat hearts. Ultrasound and histologic analysis of transmural myocardial wedge samples confirmed that the apparent backscatter could be reproducibly mapped to fiber orientation (angle of the fiber relative to the direction of insonification). These data provided a quantitative relationship between the apparent backscatter and fiber angle that was applied to whole-heart images. Myocardial fiber architecture was successfully measured in rat hearts. Quantifying myocardial fiber architecture, using apparent backscatter, provides a number of advantages, including its scalable use from rodents to man, its rapid low-cost acquisition and minimal contraindications. The method outlined in this study provides a method for investigators to begin detailed assessments of how the myocardial fiber architecture changes in preclinical disease models, which can be immediately translated into the clinic.     

Three‐dimensional imaging of the mouse heart and vasculature using micro‐CT and whole‐body perfusion of iodine or phosphotungstic acid

Recent studies have investigated histological staining compounds as micro‐computed tomography (micro‐CT) contrast agents, delivered by soaking tissue specimens in stain and relying on passive diffusion for agent uptake. This study describes a perfusion approach using iodine or phosphotungstic acid (PTA) stains, delivered to an intact mouse, to capitalize on the microvasculature as a delivery conduit for parenchymal staining and direct contact for staining artery walls. Twelve C57BL/6 mice, arterially perfused with either 25% Lugol's solution or 5% PTA solution were scanned intact and reconstructed with 26 µm isotropic voxels. The animals were fixed and the heart and surrounding vessels were excised, embedded and scanned; isolated heart images were reconstructed with 13 µm isotropic voxels. Myocardial enhancement and artery diameters were measured. Both stains successfully enhanced the myocardium and vessel walls. Interestingly, Lugol's solution provided a significantly higher enhancement of the myocardium than PTA [2502 ± 437 vs 656 ± 178 Hounsfield units (HU); p < 0.0001], delineating myofiber architecture and orientation. There was no significant difference in vessel wall enhancement (Lugol's, 1036 ± 635 HU; PTA, 738 ± 124 HU; p = 0.29), but coronary arteries were more effectively segmented from the PTA‐stained hearts, enabling segmented imaging of fifth‐ order coronary artery branches. The combination of whole mouse perfusion delivery and use of heavy metal‐containing stains affords high‐resolution imaging of the mouse heart and vasculature by micro‐CT. The differential imaging patterns of Lugol's‐ and PTA‐stained tissues reveals new opportunities for micro‐analyses of cardiac and vascular tissues. Copyright © 2014 John Wiley & Sons, Ltd.     

Incidence and characteristics of left ventricular false tendons and trabeculations in the normal and pathologic heart by second harmonic echocardiography.

We sought to review echocardiographic incidence of anomalous images (AI) as false tendons and trabeculations of the left ventricle (LV) in light of recent advancements in echocardiographic evaluation of heart anatomy. In 1580 patients the presence of false tendons, trabeculations, or thrombi was evaluated with transthoracic echocardiography and correlated to clinical characteristics and echocardiographic parameters. Incidence of AI was 46.7% (75% false tendons, 23% trabeculations, 2% thrombi), slightly higher in pathologic (48.9%) than in normal hearts (40.8%). AI were more frequent in male patients (52%) than in female patients (39.7%) and associated with LV dilatation, hypertrophy, and systolic dysfunction. False tendons and trabeculations were not related to age. Male sex was the most significant independent predictor of AI. In 2 patients, isolated LV noncompaction of myocardium was diagnosed and confirmed by magnetic resonance imaging. This study shows a high prevalence of AI for patients with and without pathologic hearts suggesting the need of updating LV echocardiographic anatomy. It also emphasizes the necessity for an awareness of these anatomic variants when evaluating patients for mural thrombi and cardiomyopathies.     

Histology validation of mapping depth-resolved cardiac fiber orientation in fresh mouse heart using optical polarization tractography

Myofiber organization in cardiac muscle plays an important role in achieving normal mechanical and electrical heart functions. An imaging tool that can reveal microstructural details of myofiber organization is valuable for both basic research and clinical applications. A high-resolution optical polarization tractography (OPT) was recently developed based on Jones matrix optical coherence tomography (JMOCT). In this study, we validated the accuracy of using OPT for measuring depth-resolved fiber orientation in fresh heart samples by comparing directly with histology images. Systematic image processing algorithms were developed to register OPT with histology images. The pixel-wise differences between the two tractographic results were analyzed in details. The results indicate that OPT can accurately image depth-resolved fiber orientation in fresh heart tissues and reveal microstructural details at the histological level.OCIS codes: (110.4500) Optical coherence tomography, (230.5440) Polarization-selective devices, (170.6935) Tissue characterization     

心脏三维超声虚拟内窥镜系统导航与介入方法研究

目的通过心脏三维超声虚拟内窥镜系统导航和介入方法研究,旨在探索并建立复杂型先心病虚拟现实环境下观察的规范化"路径"和介入方法。方法采用体绘制技术重建心腔内表面的三维图像,并置感兴趣的心内结构于可视化显示窗中心,键盘操作与人工导航结合使三维重建图像沿着视线方向前进,产生被观察心内结构目标不断靠近观察者和放大的多帧图像。结果系统通过控制鼠标、键盘立体定位,结合VanPraagh"节段分析法"对感兴趣区域观察,使操作者在虚拟心脏内漫游,实现部分心内畸形结构的诊断。对诊断房、室间隔缺损者,应用虚拟介入装置模拟ASD、VSD介入治疗。结论三维超声虚拟内窥镜为先天性心脏病临床诊断、术前模拟介入、手术计划、外科手术导航及计算机辅助医学教学提供了一种新方法。     

Quantitative comparison of myocardial fiber structure between mice,rabbit, and sheep using diffusion tensor cardiovascular magnetic resonance

Background

Accurate interpretations of cardiac functions require precise structural models of the myocardium, but the latter is not available always and for all species. Although scaling or substitution of myocardial fiber information from alternate species has been used in cardiac functional modeling, the validity of such practice has not been tested.

Methods

Fixed mouse (n = 10), rabbit (n = 6), and sheep (n = 5) hearts underwent diffusion tensor imaging (DTI). The myocardial structures in terms of the left ventricular fiber orientation helix angle index were quantitatively compared between the mouse rabbit and sheep hearts.

Results

The results show that significant fiber structural differences exist between any two of the three species. Specifically, the subepicardial fiber orientation, and the transmural range and linearity of fiber helix angles are significantly different between the mouse and either rabbit or sheep. Additionally, a significant difference was found between the transmural helix angle range between the rabbit and sheep. Across different circumferential regions of the heart, the fiber orientation was not found to be significantly different.

Conclusions

The current study indicates that myocardial structural differences exist between different size hearts. An immediate implication of the present findings for myocardial structural or functional modeling studies is that caution must be exercised when extrapolating myocardial structures from one species to another.     

How to perform an accurate assessment of cardiac function in mice using high-resolution magnetic resonance imaging.

High-resolution magnetic resonance cine imaging (cine-MRI) is a method that allows for a non-invasive assessment of left ventricular function and mass. To perform this quantitation, hearts are imaged from the base to the apex by a stack of two-dimensional images. Thus, analysis of myocardial mass and function by cine-MRI does not rely on geometric assumptions. Geometric and functional parameters, such as end-diastolic volume (EDV), end-systolic volume (ESV) or ejection fraction (EF), are obtained by subsequent image segmentation of the respective cine frames in each slice. While this technique has been well established in clinical practice, it is now rapidly becoming the reference method in experimental cardiovascular MRI for accurate quantification of cardiac parameters, thereby aiding the phenotyping of the increasing number of transgenic and surgical mouse models. However, accurate measurement of cardiac functional parameters requires the images to be acquired in short-axis orientation of the heart, which can be difficult to define, particularly in animals with diseased hearts. Furthermore, data analysis can be the source of a systematic error, mainly for myocardial mass measurement. Here, we describe a protocol that allows for a quick and reproducible approach of obtaining the relevant cardiac views for cine-MRI, and we explain how an accurate experimental image analysis can be performed.     

Estimation of left ventricular compliance using on-line echocardiographic automated border detection and pressure data

The end-diastolic pressure-volume relationship can be used to describe left ventricular (LV) compliance. The objective of this study was to utilize measurements of LV cavity area by echocardiographic automated border detection and pressure data to estimate the end-diastolic pressure-volume curve in an isolated heart preparation where true volume could be measured by an intraventricular balloon. Six dog hearts were excised for placement of an intraventricular balloon and a micromanometer catheter and perfused in anex vivo circuit. Mid-ventricular short-axis images were used to measure cross-sectional area by automated border detection while LV volumes were increased from 5 ml to maximal volume (30–40 ml) in each preparation. Simultaneous area and pressure data were recorded on a computer workstation through a customized interface with the ultrasound system. Three runs of varying LV volumes at 1 ml increments were performed on each of 6 hearts for a total of 1,080 simultaneous measurements. Pressure-volume and pressure-area curves were analyzed by linear regression analyses, the slope of which was used to estimate compliance. End-diastolic pressure-area and pressure-volume relationships were significantly correlated with mean r=0.97 ± 0.02 (p<0.001) from individual hearts. The slopes which served to estimate compliance of the individual pressure-area and pressure-volume curves were similar and differed by only 7±4%. A similar correlation was observed by second order regression analyses with r=0.97±0.01 (p<0.001) for pressure-area and r=0.98±0.01 (p<0.001) for pressure-volume relationships. The end-diastolic pressure-area curves may potentially be used to estimate LV compliance, although the clinical application of this method remains to be validated.     

复杂畸形胎儿心脏超声解剖教学标本的制作与实践

目的 将临床确诊并引产的复杂畸形胎儿心脏制作成与心脏超声切面观一致的解剖教学标本,并应用于超声心动图教学.方法 分别对10例引产胎儿心脏按照不同超声切面观进行切割,与超声图像对照.结果 获得5例单心室(2例伴主动脉弓离断)、4例右室双出口并肺动脉发育不良、1例左室发育不良伴主动脉重度缩窄等复杂畸形胎儿心脏对照超声的解剖标本.心尖长轴观、三血管切面以及主动脉弓长轴观为超声诊断与教学的典型切面.结论 通过对复杂畸形胎儿心脏超声解剖标本的研究与制作,有助于超声专业初学者熟练掌握复杂畸形胎儿心脏各个部位解剖结构,形象化理解超声影像特点,有利于进一步提高复杂畸形胎儿心脏超声检查的准确性.     

Direct three-dimensional myocardial strain tensor quantification and tracking using zHARP

Images of myocardial strain can be used to diagnose heart disease, plan and monitor treatment, and to learn about cardiac structure and function. Three-dimensional (3D) strain is typically quantified using many magnetic resonance (MR) images obtained in two or three orthogonal planes. Problems with this approach include long scan times, image misregistration, and through-plane motion. This article presents a novel method for calculating cardiac 3D strain using a stack of two or more images acquired in only one orientation. The zHARP pulse sequence encodes in-plane motion using MR tagging and out-of-plane motion using phase encoding, and has been previously shown to be capable of computing 3D displacement within a single image plane. Here, data from two adjacent image planes are combined to yield a 3D strain tensor at each pixel; stacks of zHARP images can be used to derive stacked arrays of 3D strain tensors without imaging multiple orientations and without numerical interpolation. The performance and accuracy of the method is demonstrated in vitro on a phantom and in vivo in four healthy adult human subjects.     

自然组织谐波显像的临床应用价值

目的：研究超声心动图检查中自然组织谐波显像（NTHI）改善图像质量是否有程度的差异。方法：经胸用基波显像（FI）及NTHI对比分析成像条件不同的80例二维超声心动图的胸骨旁左室长轴切面（LAX）、心尖两腔切面（AP2）和心尖四腔切面（AP4）及22个不同节段的内膜可视度（EV）及心内结构清晰度。内膜EV根据内膜不可见、可见、清晰分为1、2、3分。结果：NTHI能明显提高总的及不同切面的EV,所有22个节段EV也明显改善,但改善程度以AP2、AP4及其基底段、中段最佳;图像质量差的比图像质量好的心内结构改善更明显。但NTHI示心内结构稍显增厚,彩色血流显像不丰富。结论：支持NTHI能显著改善超声心动图二维图像,但不同节段、不同切面及成像条件不同的患者改善程度不同,因使心内结构稍显增厚,判断是否有病理改变时应注意。     

Three-dimensional cardiac anatomy and function in heart disease in adults: initial results with the dynamic spatial reconstructor

The dynamic spatial reconstructor, or DSR, is a unique high-speed volume-imaging x-ray scanner based on computed tomographic principles. In this report, we present data obtained from the first feasibility DSR studies of adult patients with heart disease. Information from three patients--one with hypertrophic obstructive cardiomyopathy, one with calcific aortic valvular disease, and one with a left ventricular aneurysm--is described in detail. The mean DSR scanning time for each patient was 20 seconds, and the mean total irradiation to the sternum was 15.3 R. Transverse cross sections were reconstructed and then retrospectively reformatted to provide operator-selected oblique sections in space (for example, long-axis and short-axis sections of the left ventricle), to follow these sections through time (such as from end-diastole through end-systole), and to create three-dimensional displays (for instance, of the left ventricular chamber). Unique quantitative measurements of structure and function were made by using these images. For generation of most imaging data, only one injection of contrast material into the right side of the heart is necessary. Clinically useful three-dimensional dynamic imaging data can be acquired from adult patients with heart disease by using the DSR. Compared with conventional angiocardiography, DSR studies can provide information with less x-ray exposure and fewer angiographic injections.     

Ultrafast Ultrasound Imaging for Super-Resolution Preclinical Cardiac PET

Purpose

Physiological motion and partial volume effect (PVE) significantly degrade the quality of cardiac positron emission tomography (PET) images in the fast-beating hearts of rodents. Several Super-resolution (SR) techniques using a priori anatomical information have been proposed to correct motion and PVE in PET images. Ultrasound is ideally suited to capture real-time high-resolution cine images of rodent hearts. Here, we evaluated an ultrasound-based SR method using simultaneously acquired and co-registered PET-CT-Ultrafast Ultrasound Imaging (UUI) of the beating heart in closed-chest rodents.

Procedures

The method was tested with numerical and animal data (n?=?2) acquired with the non-invasive hybrid imaging system PETRUS that acquires simultaneously PET, CT, and UUI.

Results

We showed that ultrasound-based SR drastically enhances the quality of PET images of the beating rodent heart. For the simulations, the deviations between expected and mean reconstructed values were 2 % after applying SR. For the experimental data, when using Ultrasound-based SR correction, contrast was improved by a factor of two, signal-to-noise ratio by 11 %, and spatial resolution by 56 % (~?0.88 mm) with respect to static PET. As a consequence, the metabolic defect following an acute cardiac ischemia was delineated with much higher anatomical precision.

Conclusions

Our results provided a proof-of-concept that image quality of cardiac PET in fast-beating rodent hearts can be significantly improved by ultrasound-based SR, a portable low-cost technique. Improved PET imaging of the rodent heart may allow new explorations of physiological and pathological situations related with cardiac metabolism.

     

Muscle fiber orientation in normal and hypertrophied hearts.

Muscle fiber orientation in the left ventricular myocardial layer was histometrically estimated in normal, concentric and eccentric hypertrophied hearts. The angle of inclination of muscle fibers from coronal section was largest in the innermost and outermost zones and was progressively diminished toward the middle layer in all the hearts. In the inner layer, the inclination was depressed in eccentric hypertrophy, while there was no difference in fiber orientation in the outer layer. Concentric hypertrophy proved to be an intermediate stage between the normal heart and eccentric hypertrophy, and no opposite behavior was found in the arrangement of heart muscle fibers. The results supported the following view on the mechanism in the activity of hypertrophied hearts. Cardiac hypertrophy is a common accommodation process to increased load, regardless of the difference in the macroscopical shape. In hypertrophy, the ventricular cavity is inevitably enlarged. Consequently, the tension exerted on the ventricular wall on account of intraventricular pressure increases, and the contractile force required from a unit thickness of the ventricular wall is enhanced. The muscle fibers meet this increased demand by starting contraction from an over-stretched state and by ceasing its activity after smaller shortening than in the normal heart.     

三维超声仿真心腔内窥镜技术诊断房间隔缺损的实验研究

目的 探讨三维超声虚拟现实技术实现仿真心腔内窥镜观测房间隔缺损（ASD）的可行性。方法建立10个新鲜离体猪心ASD模型，经超声水槽用HP Sonos 5500超声系统采集三维超声图像，用移动立方体算法进行表面重建及可视化，建立心内三维超声仿真心腔内窥镜系统；同时将该系统的ASD面积、最大径和最小径测值与实测值进行比较。结果10例离体心ASD均成功获得虚拟显示。三维超声虚拟现实技术能够模拟心内视角显示缺损的形态、部位及邻近上腔静脉、下腔静脉间的关系，且与实际观察结果一致。测量三维重建并虚拟显示后的ASD面积、最大径和最小径，测得数据与实测值高度相关（r〉0．95，P〈0．01）。结论三维超声仿真心腔内窥镜技术为小儿先天性心脏病三维超声诊断提供了一种新方法。     

动态心内三维超声虚拟现实诊断方法研究

目的应用虚拟现实（VR）技术,通过临床初步应用研究,评价小儿先天性心脏病心内三维虚拟现实诊断方法的可行性.方法正常小儿20例、先天性心脏病患儿30例（ASD 10例、VSD 9例、TOF 11例）,分别进行全心三维图像重建,实现动态三维超声虚拟现实显示,对虚拟心内结构进行三维空间定位观察,显示心内结构异常者与心导管术后或手术后诊断或三维超声诊断进行比较,确定该方法的空间定位及空间结构关系判断的准确性.结果动态心内三维超声虚拟显示技术能正确显示正常及先天性心脏病患儿的心内结构,诊断心内结构异常者与心导管术后或手术后诊断或三维超声诊断一致.结论动态心内三维超声虚拟现实技术为小儿先天性心脏病无创性三维超声诊断提供了一种新方法.     

Validation of diffusion spectrum magnetic resonance imaging with manganese-enhanced rat optic tracts and ex vivo phantoms

Diffusion spectrum imaging (DSI) has been demonstrated to resolve crossing axonal fibers by mapping the probability density function of water molecules diffusion at each voxel. However, the accuracy of DSI in defining individual fiber orientation and the validity of Fourier relation under finite gradient pulse widths are not assessed yet. We developed an ex vivo and an in vivo model to evaluate the error of DSI with gradient pulse widths being relatively short and long, respectively. The ex vivo model was a phantom comprising sheets of parallel capillaries filled with water. Sheets were stacked on each other with capillaries crossed at 45 degrees or 90 degrees. High-resolution T2-weighted images (T2WI) of the phantom served as a reference for the orientation of intersecting capillaries. In the in vivo model, manganese ions were infused into rats' optic tracts. The optic tracts were enhanced on T1-weighted images (T1WI) and served as a reference for the tract orientation. By comparing DSI with T2WI, the deviation angles between the primary orientation of diffusion spectrum and the 90 degrees and 45 degrees phantoms were 1.19 degrees +/- 4.82 degrees and -0.71 degrees +/- 4.91 degrees, respectively. By comparing DSI with the T1WI of rat optic tracts, the deviation angle between primary orientation of diffusion spectrum and optic tracts was -0.41 degrees +/- 6.18 degrees. In addition, two sequences of DSI using short and long gradient pulses were performed in a rat brain. The bias of the primary orientation between these two sequences was approximately 10 degrees. In conclusion, DSI can resolve crossing fiber orientation accurately. The effect of finite gradient pulse widths on the primary orientation is not critical.     

White matter fiber tracts of the human brain: three-dimensional mapping at microscopic resolution, topography and intersubject variability

The position and extent of individual fiber tracts within the white matter of human brains can be identified in vivo using diffusion tensor imaging (DTI) and fiber tracking methods. Previous to this study, however, the lack of three-dimensional (3-D) probability maps precluded comparing the anatomical precision of MRI studies with microscopically defined fiber tracts in human postmortem brains. The present study provides 3-D registered maps of the topography, course and intersubject variability of major fiber tracts, which were identified at microscopic resolution. The analyzed tracts include the corticospinal tract, optic and acoustic radiations, fornix, cingulum, corpus callosum, superior longitudinal, superior and inferior occipito-frontal and uncinate fascicles; sources and targets of fiber tracts include the lateral and medial geniculate nuclei and mamillary bodies. Tracts and nuclei were identified in serial myelin-stained histological sections of ten postmortem brains. The sections were 3-D reconstructed and registered to a standardized stereotaxic space of an in vivo MR reference brain by means of linear and non-linear, elastic transformations. The individual fiber tracts and nuclei were superimposed in the reference space, and probability maps were generated as a quantitative measure of intersubject variability for each voxel of the stereotaxic space. This study presents the first stereotaxic atlas of the course, location and extent of fiber tracts and related nuclei based on microscopically defined localization and topographic data taken at multiple levels on each of the three orthogonal planes. The maps are useful for evaluating and identifying fiber bundles in DTI, for localizing subcortical lesions visible in anatomical MR images and for studying neuronal connectivity.