Dolores H. Pretorius

Three-dimensional ultrasound imaging

The objective of this article is to provide scientists, engineers and clinicians with an up-to-date overview on the current state of development in the area of three-dimensional ultrasound (3-DUS) and to serve as a reference for individuals who wish to learn more about 3-DUS imaging. The sections will review the state of the art with respect to 3-DUS imaging, methods of data acquisition, analysis and display approaches. Clinical sections summarize patient research study results to date with discussion of applications by organ system. The basic algorithms and approaches to visualization of 3-D and 4-D ultrasound data are reviewed, including issues related to interactivity and user interfaces. The implications of recent developments for future ultrasound imaging/visualization systems are considered. Ultimately, an improved understanding of ultrasound data offered by 3-DUS may make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed networks to review volume ultrasound data at specialization centers. Access to volume data and expertise at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment.

Three-dimensional ultrasound

The papers in this issue show that the feasibility of three-dimensional ultrasound methods in the clinical setting using commercially available equipment is nearby. Their results demonstrate some of the advantages compared to two-dimensional ultrasound and other diagnostic modalities, including reduced scanning times that will offer more cost-effective use of equipment and sonographer time. Other benefits of three-dimensional ultrasound include allowing the physician: to evaluate arbitrary planes not available with two-dimensional ultrasound due to patient body habitus; to measure organ dimensions and volumes; to obtain anatomic and blood flow information; to improve assessment of complex anatomic anomalies; to confirm normalcy; to standardized the ultrasound exam procedures; to enhance the understanding of physicians in primary care facilities and communicate volume data over networks for consultation at tertiary facilities. Standardization of the ultrasound examination protocols can lead to uniformly high-quality examinations and decreased health care costs. Ultimately, three-dimensional ultrasound imaging will make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed computer networks to review volume or dynamic data at specialization centers with primary care physicians. Access to volume data at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment and reducing health care costs.

Three-dimensional echocardiographic evaluation of fetal heart anatomy and function : acquisition, analysis, and display

The purpose of this work was to assess the functional dynamics and anatomy of the cardiac chambers and great vessels in the fetus (18 to 36 weeks) using in utero three-dimensional ultrasonographic imaging. Fifteen patients were studied using conventional two-dimensional sonographic equipment incorporating a position sensor attached to the transducer and a graphics workstation. Sonographic image data were acquired at 30 images per second and required less than 30 seconds per data set. Fetal heart rate and time in the cardiac cycle were determined and used to synchronize image data for reprojection into a volume at the appropriate part of the cardiac cycle. Volume data were analyzed, rendered, and displayed interactively. Three-dimensional sonographic volume data demonstrated fetal cardiac anatomy from multiple orientations and showed the myocardium, valves, ventricles, and atria clearly. The images showed good correlation with currently available embryologic-anatomic-pathologic data. Dynamic and spatial relationships among chambers, valves, and great vessels were readily appreciated. Three-dimensional sonographic imaging of the fetal heart provides both anatomic and functional information regarding the valves, myocardium, great vessels, and chamber dynamics. Interactive three-dimensional cinegraphic display enhances visualization of cardiac anatomy, which can be difficult to appreciate with two-dimensional methods. The methods presented in this work demonstrate the feasibility of three-dimensional fetal echocardiography.

Distance and volume measurement using three-dimensional ultrasonography.

The purpose of this study was to assess the accuracy of distance and volume measurements obtained by three‐dimensional ultrasonography. A tissue‐mimicking phantom was scanned using a prototype three‐dimensional sonographic imaging system to verify distance measurements. Measurements were taken from the reconstructed three‐dimensional sonographic data and compared to the real distances. Volume measurements were obtained by scanning 30 balloons of various shapes, sized 23 ml to 2400 ml. Each balloon was scanned twice in two orientations; three different masks were accomplished for each volume. Each volume measurement of 180 three‐dimensional sonographic measurements was compared to conventional two‐dimensional ultrasonographic volume estimates and to the actual, measured balloon size. Distance measurements had a mean error of 0.02 +/‐ 3.65% (range, ‐4.27 to 7.18%). Two‐dimensional sonographic volume estimates using traditional scanner based methods had a mean error of 13.7 +/‐ 10.1%. Three‐dimensional sonographic volume measurements had a mean error of 2.2 +/‐ 2.9% for regular and irregular objects over the entire range of volumes. The masking required 10 to 30 min. The field of view varied from 10 to 24 cm with a mean object depth of 9.8 cm. Three‐dimensional ultrasonographic methods can provide accurate volume measurements of regular and irregular objects and offer improved accuracy compared to traditional two‐dimensional methods.

In vivo three-dimensional sonographic measurement of organ volume: validation in the urinary bladder.

The purpose of this study was to assess the accuracy of in vivo measurement of organ volume using 3DUS and compare the results to 2D sonographic methods using the urinary bladder as the target organ and voided urine volume for validation. Fifty normal volunteers were studied. 2D volume measurements were based on length, width, and depth data and assumed a regular geometric model. 3D volume measurements were based on masked slices with the voxels integrated over the entire bladder. Voided urine volumes ranged from 35 ml to 701 ml. Residual urine volume was present in 48% of the subjects and ranged from 1% to 14% of the voided volume. 2D volume estimates for all 50 subjects had a mean absolute value of the error of 27.5% +/‐ 17.8%. 3D volume measurements had a mean absolute value of the error of 4.3% +/‐ 3.7% (transverse) and 5.6% +/‐ 3.8% (longitudinal). 3DUS provided more accurate volume measurements than 2DUS, particularly for irregularly shaped organs.

Diagnostic criteria for nonviable pregnancy early in the first trimester.

Determining the viability of a pregnancy is a major challenge, especially with a pregnancy of unknown location. This review provides specific guidance, including stringent criteria for nonviability, that can reduce the risk of inadvertent harm to a potentially normal pregnancy.

Three- and 4-Dimensional Ultrasound in Obstetrics and Gynecology Proceedings of the American Institute of Ultrasound in Medicine Consensus Conference

The American Institute of Ultrasound in Medicine convened a panel of physicians and scientists with interest and expertise in 3‐dimensional (3D) ultrasound in obstetrics and gynecology to discuss the current diagnostic benefits and technical limitations in obstetrics and gynecology and consider the utility and role of this type of imaging in clinical practice now and in the future. This conference was held in Orlando, Florida, June 16 and 17, 2005. Discussions considered state‐of‐the‐art applications of 3D ultrasound, specific clinical situations in which it has been found to be helpful, the role of 3D volume acquisition for improving diagnostic efficiency and patient throughput, and recommendations for future investigations related to the utility of volume sonography in obstetrics and gynecology.

Interactive acquisition, analysis, and visualization of sonographic volume data

This article discusses the design features of an interactive system for acquiring, analyzing, and displaying volume sonographic patient data. Methods for reprojection of two‐dimensional (2D) sonographic image data into a volume matrix are discussed. We describe an intuitive, easy‐to‐use graphical user interface that facilitates physician operation of a system incorporating an interactive volume renderer for optimization of viewing orientation and data presentation and incorporates stereoscopic viewing. Visualization methods are described that permit the operator interactively to extract tissues or organs of interest from the rest of the volume scanned. Selected examples of clinical images are given to demonstrate system capability. The system represents a cost‐effective 3D ultrasound system integrating clinical scanners and graphics workstations.

Real-time three-dimensional fetal echocardiography: initial feasibility study.

Real‐time three‐dimensional echocardiography acquires data as a volume rather than as a series of planar images, thereby obviating cardiac or respiratory gating and limiting artifacts generated by random motion. This study was undertaken to evaluate the feasibility of using real‐time three‐dimensional echocardiography to evaluate fetal cardiac anatomy and function. Ten human fetuses were evaluated in utero, four of whom had congenital heart disease. Freehand transabdominal scanning was performed on each pregnant woman using a real‐time three‐dimensional echocardiography system. Four volume clips at 20 volumes/s of duration 1.5 s each were obtained on each fetal heart and stored for off‐line analysis. Data were displayed immediately as a series of four simultaneous planes, with the ability for the observer to manipulate the position of each plane within the acquired volume data set. Cardiac motion could be slowed, stopped, or viewed at its original speed. Most structures and views, as well as cardiac function, could be visualized consistently. Abnormal structures could be detected readily. Off‐line analysis was rapid and easy. We conclude that fetal real‐time three‐dimensional echocardiography is a feasible, facile, and rapid new technique.

Improving cleft palate/cleft lip antenatal diagnosis by 3-dimensional sonography: the "flipped face" view.

Objective. Three‐dimensional sonography has enhanced the diagnosis of congenital anomalies in the early stages of pregnancy. Both cleft lip and palate remain a diagnostic challenge for the sonographer because of the variable size of the defects as well as their location. Recently, a technique described by Campbell et al (Ultrasound Obstet Gynecol 2003;:–554, 2005; 25:12–18) demonstrated an improved method called the “reverse face” view, which appears to assist in the diagnosis of clefts involving the palate. Methods. The fetal face was initially examined with the fetus in the supine position. Using 3‐dimensional sonography, a static volume was acquired. Following acquisition of the volume, it was rotated 90° so that the cut plane was directed in a plane from the chin to the nose. The volume cut plane was then scrolled from the chin to the nose to examine in sequential order the lower lip, mandible, and alveolar ridge; tongue; upper lip, maxilla, and alveolar ridge; and hard and soft palates. Results. This approach identified the full length and width of the structures of the mouth and palates and allows the examiner to identify normal anatomy as well as clefts of the hard and soft palates. Conclusions. The fetal hard and soft palates of the mouth can be accessed using a new technique, which we call the “flipped face” maneuver, when an adequate volume of the face can be obtained.