'Wakey wakey baby': narrating four-dimensional (4D) bonding scans.

Commercial companies market 4D ultrasound scans to expectant parents for the stated purpose of reassurance, to promote bonding, and to get 'baby's first picture'. This article describes in detail the process of commercial 4D scanning in the UK, paying particular attention to the discursive exchanges in the scan room. It is argued that sonographers and clients engage in a process of 'collaborative coding' that, despite the realism of 4D, is essential to making the imagery on the screen personally and socially meaningful. While sonographers first help clients to get their bearings, expectant parents and others often engage in a complex process of narrating the images on the screen as they are created. The capacities of 4D ultrasound to image facial features and movements inform stories about fetal experience and family resemblances as well as enabling playfully imagined interactions with the fetus. While these stories are primarily based in experiences of the visual, there is also evidence that pregnant women seek to map the image onto their bodies and to reintroduce some elements of their embodied experiences into the narratives.

A 10-Fr ultrasound catheter with integrated micromotor for 4-D intracardiac echocardiography.

We developed prototype real-time 3-D intracardiac echocardiography catheters with integrated micromotors, allowing internal oscillation of a low-profile 64-element, 6.2-MHz phased-array transducer in the elevation direction. Components were designed to facilitate rotation of the array, including a low-torque flexible transducer interconnect and miniature fixtures for the transducer and micromotor. The catheter tip prototypes were integrated with two-way deflectable 10-Fr catheters and used in in vivo animal testing at multiple facilities. The 4-D ICE catheters were capable of imaging a 90° azimuth by up to 180° elevation field of view. Volume rates ranged from 1 vol/sec (180° elevation) to approximately 10 vol/sec (60° elevation). We successfully imaged electrophysiology catheters, atrial septal puncture procedures, and detailed cardiac anatomy. The elevation oscillation enabled 3-D visualization of devices and anatomy, providing new clinical information and perspective not possible with current 2-D imaging catheters.

Fetal cardiac ventricular volume, cardiac output, and ejection fraction determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis.

OBJECTIVE: The objective of this study was to quantify fetal cardiovascular parameters using spatiotemporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL). STUDY DESIGN: A cross-sectional study was performed in normal pregnancies (19-42 weeks) to evaluate ventricular volume, stroke volume (SV), cardiac output (CO), and ejection fraction (EF). The CO was also expressed as a function of estimated fetal weight and biometric parameters. RESULTS: The following results were found: (1) 184 STIC datasets; (2) with advancing gestation, ventricular volume, SV, CO, and adjusted CO increased, whereas EF decreased; (3) right ventricular (RV) volume was larger than the left ventricular (LV) volume in systole (0.50 vs 0.27 mL; P < .001) and diastole (1.20 vs 1.03 mL; P < .001); (4) there were no differences between the LV and RV in SV, CO, or adjusted CO; and (5) LV EF was greater than the RV EF (72.2 vs 62.4%; P < .001). CONCLUSION: Normal fetal cardiovascular physiology is characterized by a larger RV volume and a greater LV EF, resulting in similar LV and RV SV and CO.

Fetal cardiac function assessed with four-dimensional ultrasound imaging using spatiotemporal image correlation.

OBJECTIVES: The goal of this study was to use spatiotemporal image correlation (STIC) to provide reference values for left and right ventricle volumes, and indices of fetal cardiac function. METHODS: In this prospective longitudinal study, STIC volumes were acquired periodically from 12 weeks of gestation onwards. The STIC volumes were frozen in end-systole and end-diastole, and volumetric data were measured by manual tracing and summation of multiple slices. These ventricle volumes were used to calculate stroke volume, ejection fraction and cardiac output. RESULTS: Some 202 STIC volumes of 63 fetuses were included in the analysis. Mean left and right ventricle stroke volume increased from 0.02 mL at 12 weeks to 1.41 mL and 1.46 mL, respectively, at 30 weeks, while the mean right to left stroke volume ratio remained stable at around 1.2. Mean left and right ventricle cardiac output increased from 2.40 mL/min and 2.60 mL/min at 12 weeks to 197.74 mL/min and 204.81 mL/min, respectively, at 30 weeks. Both left and right mean ejection fraction remained constant at around 0.45 with advancing gestational age. Bland-Altman analysis showed a coefficient of variation for measured stroke volume of 13.7%. CONCLUSIONS: This study establishes reference values for fetal cardiac volumes and indices for fetal cardiac function from 12 to 30 weeks of gestation using STIC. STIC seems to overcome many of the pitfalls of conventional ultrasound methods and has the potential to become the method of choice.

Medical image computing for computer-supported diagnostics and therapy. Advances and perspectives.

OBJECTIVES: Medical image computing has become one of the most challenging fields in medical informatics. In image-based diagnostics of the future software assistance will become more and more important, and image analysis systems integrating advanced image computing methods are needed to extract quantitative image parameters to characterize the state and changes of image structures of interest (e.g. tumors, organs, vessels, bones etc.) in a reproducible and objective way. Furthermore, in the field of software-assisted and navigated surgery medical image computing methods play a key role and have opened up new perspectives for patient treatment. However, further developments are needed to increase the grade of automation, accuracy, reproducibility and robustness. Moreover, the systems developed have to be integrated into the clinical workflow. METHODS: For the development of advanced image computing systems methods of different scientific fields have to be adapted and used in combination. The principal methodologies in medical image computing are the following: image segmentation, image registration, image analysis for quantification and computer assisted image interpretation, modeling and simulation as well as visualization and virtual reality. Especially, model-based image computing techniques open up new perspectives for prediction of organ changes and risk analysis of patients and will gain importance in diagnostic and therapy of the future. RESULTS: From a methodical point of view the authors identify the following future trends and perspectives in medical image computing: development of optimized application-specific systems and integration into the clinical workflow, enhanced computational models for image analysis and virtual reality training systems, integration of different image computing methods, further integration of multimodal image data and biosignals and advanced methods for 4D medical image computing. CONCLUSIONS: The development of image analysis systems for diagnostic support or operation planning is a complex interdisciplinary process. Image computing methods enable new insights into the patient's image data and have the future potential to improve medical diagnostics and patient treatment.

Ultrasound image and augmented reality guidance for off-pump, closed, beating, intracardiac surgery.

Our project is the reintroduction of off-pump intracardiac surgery using the Universal Cardiac Introducer (UCI) for safe intracardiac access. The purpose of this study was to evaluate multimodality visualization using three ultrasound modalities and ultrasound augmented with virtual reality. Image guidance was tested on implanting a mitral valve prosthesis via the UCI in 12 pigs. Initially, two-dimensional (2-D) transesophageal echocardiography (TEE) ultrasound, intravascular ultrasound (intracardiac echocardiography [ICE]), and three-dimensional (3-D) epicardial ultrasound were utilized. Ultrasound augmented with virtual reality was used in the last three experiments. A 2-D TEE assisted navigating the prosthesis into the orifice. Positioning was not intuitive and required trial and error method. A 3-D epicardial ultrasound allowed positioning of the valve into the orifice. Positioning of the clip was difficult because of artifacts with multiple reflections and shadowing. Augmented reality displayed the entire prosthesis and the tools without artifacts; provided intuitive information on navigation, positioning, and orientation of tools; and improved significantly image guidance and surgical skill. Augmented virtual reality, with tracked 2-D or 3-D ultrasound imaging, provides guidance that can effectively substitute for direct vision during beating heart intracardiac surgery.

Validating volume flow measurements from a novel semiautomated four-dimensional Doppler ultrasound scanner.

RATIONALE AND OBJECTIVES: Accurate measurement of blood volume flow (in ml/min) is an important clinical goal. This project compared in vitro and in vivo volume flow measurements obtained with a novel, real-time three-dimensional (i.e., four-dimensional) ultrasound scanner (Encore PV; Vuesonix Sensors, Wayne, PA) with those from an invasive transit time flowmeter. MATERIALS AND METHODS: A flow pump was used to generate pulsatile flow rates from 60 to 600 ml/min. The Encore detected absolute blood velocity vectors within a volume. The scanner determined the centerline of the vessel and volume flow was then automatically calculated. Results were compared with those of an invasive technique for volumetric blood flow measurements utilizing a transit-time flowmeter (TS420; Transonic Systems Inc., Ithaca, NY). In vivo, 10 second datasets of the volume flow in the distal aorta of six rabbits were obtained simultaneously with the Encore PV and the flowmeter. Data were compared using linear regression and Bland-Altman analysis (due to the lack of independence). RESULTS: In vitro, Encore and flowmeter measurements both matched the flow pump (r2 > 0.99; P < .0001) with mean errors of -11.8% and -0.3%, respectively. Marked underestimation of the true flow rates was encountered with the Encore at the lowest pump setting. In vivo mean volume flows between 10.6 and 79.3 ml/min were measured. Mean and maximum volume flows obtained with the two techniques correlated significantly (P < .0001) with r2 values of 0.86 and 0.62, respectively. The corresponding root-mean-square errors were 6.9% for mean flow and 61.2% for maximum volume flow measurements. CONCLUSION: A new semiautomated four-dimensional Doppler device has been tested in vitro and in vivo. Mean volume flow measurements with this unit are comparable to those of an invasive flowmeter.

First performance evaluation of a dual-source CT (DSCT) system.

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

Three- and four-dimensional freehand fetal echocardiography: a feasibility study using a hand-held Doppler probe for cardiac gating.

OBJECTIVE: To evaluate the clinical feasibility of the signal from a hand-held Doppler probe as a real-time tracking signal for dynamic three-dimensional (3D) (so-called four-dimensional (4D)) fetal echocardiography in a random patient cohort. METHODS: Seventy fetuses, with and without congenital heart disease, at various gestational ages (mean, 25 weeks; range, 18-38 weeks) were investigated using freehand 3D echocardiography. Time gating was achieved concurrently by obtaining a Doppler signal of the fetal heart without further signal averaging. In 10 fetuses, Doppler gating was compared to cardiotocogram (CTG)-gated 3D echo using signal averaging. Gray-scale and color Doppler dynamic 3D displays and multiplanar views were assessed according to their ability to accurately depict cardiac gating and cardiac morphology. RESULTS: In 68/70 fetuses, valid Doppler-based trigger signals were obtained. Correct cardiac gating was achieved in 231/275 (84%) 4D datasets. Doppler tracing of the fetal heart allowed beat-to-beat triggering without the necessity for signal averaging. Doppler gating detected rapid changes in the fetal heart rate more reliably than CTG gating, but was more sensitive to acoustic interference between the gating and echo-transducer when color-coded Doppler imaging was used. Image quality was highly dependent on random motion and the acoustic window. A total of 171/231 (74%) correctly gated datasets successfully demonstrated clinically useful 4D images of the fetal heart. The reconstruction of 3D and multiplanar views provided additional views not obtainable by two-dimensional imaging. CONCLUSION: These results show that a hand-held Doppler probe can be used as a reliable online gating source for 4D fetal echocardiography.

Real-time four-dimensional imaging of the heart with multi-detector row CT.

An interactive four-dimensional (4D) visualizing system for the heart was developed by the authors. The system realizes high-resolution three-dimensional (3D) imaging with temporal resolution in a beating heart by using eight or more data sets reconstructed from multi-detector row computed tomography (MDCT) with a retrospective electrocardiograph-gated reconstruction algorithm. The motion of heart walls, papillary muscles, septa, and valves can now be observed in 4D multiplanar reformations (MPRs), as with sonography, while coronary arteries, coronary sinuses, and cardiac veins can be analyzed during the optimal phase in 4D volume-rendering images, as with angiography. All parameters such as window width, window level, field of view, panning, tilt, thresholds, opacity, color, and segmentation function are completely interactive in 4D imaging. Two longitudinal views and one latitudinal view of a heart can be simultaneously visualized in the three relative 4D MPR views. These newly developed capabilities in viewing both 3D volume and temporal resolution data, functional data, and even multiphase data with registration add considerable diagnostic potential. The advent of this real-time 4D visualizing system has enhanced the capabilities of MDCT.

Cine MPR: interactive multiplanar reformatting of four-dimensional cardiac data using hardware-accelerated texture mapping.

Four-dimensional (4-D) imaging to capture the three-dimensional (3-D) structure and motion of the heart in real time is an emerging trend. We present here our method of interactive multiplanar reformatting (MPR), i.e., the ability to visualize any chosen anatomical cross section of 4-D cardiac images and to change its orientation smoothly while maintaining the original heart motion. Continuous animation to show the time-varying 3-D geometry of the heart and smooth dynamic manipulation of the reformatted planes, as well as large image size (100-300 MB), make MPR challenging. Our solution exploits the hardware acceleration of 3-D texture mapping capability of high-end commercial PC graphics boards. Customization of volume subdivision and caching concepts to periodic cardiac data allows us to use this hardware effectively and efficiently. We are able to visualize and smoothly interact with real-time 3-D ultrasound cardiac images at the desired frame rate (25 Hz). The developed methods are applicable to MPR of one or more 3-D and 4-D medical images, including 4-D cardiac images collected in a gated fashion.

Interactive visualization of four-dimensional ultrasound data.

We present a hardware-accelerated method using three-dimensional (3D) textures to visualize four-dimensional (4D) images of the heart. Novel data subdivision and caching ideas enable interactive performance even though 4D data exceed the size of 3D texture memory. The capability to visualize 4D images is critical to continued evolution and clinical acceptance of 4D imaging.

LV volume quantification via spatiotemporal analysis of real-time 3-D echocardiography.

This paper presents a method of four-dimensional (4-D) (3-D + Time) space-frequency analysis for directional denoising and enhancement of real-time three-dimensional (RT3D) ultrasound and quantitative measures in diagnostic cardiac ultrasound. Expansion of echocardiographic volumes is performed with complex exponential wavelet-like basis functions called brushlets. These functions offer good localization in time and frequency and decompose a signal into distinct patterns of oriented harmonics, which are invariant to intensity and contrast range. Deformable-model segmentation is carried out on denoised data after thresholding of transform coefficients. This process attenuates speckle noise while preserving cardiac structure location. The superiority of 4-D over 3-D analysis for decorrelating additive white noise and multiplicative speckle noise on a 4-D phantom volume expanding in time is demonstrated. Quantitative validation, computed for contours and volumes, is performed on in vitro balloon phantoms. Clinical applications of this spaciotemporal analysis tool are reported for six patient cases providing measures of left ventricular volumes and ejection fraction.

[Free hand acquisition, reconstruction and visualization of 3D and 4D ultrasound]. / Freihandakquisition, Rekonstruktion und Visualisierung von 3D- und 4D-Ultraschall.

3D Ultrasound will find in the next years a wide popularity under the medical imaging applications. The method expands the well-known sonography on the third dimension, therefore it becomes possible to generate spatial 3D views of internal organs. It is further possible to display static (3D) as well as dynamic organs (4D, e.g. pulsating heart). The clarity of the three-dimensional presentation supports very effectively the navigation. In this article we review the upgrading of conventional ultrasound devices on 3D and 4D capabilities, as well as the display of the datasets by corresponding visualisation and filtering approaches.