Echocardiography is the predominant noninvasive method of assessing cardiac structure and function. Although initially this technique resided exclusively in the domain of the cardiologist, more recently it has been increasingly utilized for point-of-care applications across different specialties.¹ The utility of point-of-care echocardiography has been demonstrated by neonatologists in the neonatal intensive care unit,² anesthesiologists during the perioperative period,³ intensivists in the critical care setting,⁴ and emergency medicine physicians in the emergency care setting.⁵ The development of more advanced and portable systems has facilitated this change. However, the widespread use of point-of-care echocardiography, especially for neonatal intensive care, has been hampered by the lack of adequately trained non-cardiology specialists and access to patients.

Training in neonatal point-of-care echocardiography (also known as “targeted” or “functional” echocardiography) is a complex process that requires not only comprehensive theoretical knowledge but also extensive hands-on training to acquire the all-important technical skills. At present, there is no alternative method for achieving technical competence in neonatal echocardiography other than performing studies on actual neonates. However, because of the restricted access to live subjects, particularly neonates, opportunities for practical training are limited. To overcome this obstacle, echocardiography simulators have been developed. Weidenbach et al⁶ introduced two-dimensional (2D) echocardiography simulation by the use of real three-dimensional (3D) image volumes, which have been used both for transthoracic and transesophageal echocardiography.⁷ In infants and younger children, simulators based on real 3D volumes have been used for training physicians with minimal echocardiography experience with good results. The knowledge of cardiac anatomy as depicted by echocardiography and detection of congenital heart defects is improved, while spatial orientation and hand-eye coordination is enhanced by the use of the simulators.^8–10 However, presently available transthoracic echocardiographic simulators based on real 3D volumes are restricted to 2D echocardiography, which lacks other modalities such as color flow Doppler, spectral Doppler, and M-mode. Furthermore, since image volumes are obtained either from subcostal or apical windows, simulation of echocardiography from parasternal and suprasternal windows may be suboptimal. In general, real transthoracic echocardiographic images obtained in older children and adults are of poor quality and are not suitable for simulation. For these reasons, for transthoracic echocardiography, almost all commercially available simulators obtain their 3D images from other imaging platforms such as MRI and render them to look like echocardiograms. These simulators are used extensively in training intensivists, emergency room physicians, and anesthesiologists, as well as cardiology technologists and trainees.

Recently, Weidenbach et al have introduced a training simulator for echocardiography in neonates.¹¹ Although this simulator includes extensive cases of congenital cardiac defects, along with cases of functional and acquired heart diseases, it only simulates 2D echocardiography for anatomical diagnosis and has the above limitations. In spite of these limitations, it is used by neonatologists for training purposes.

We have developed a simulator with exclusive emphasis on neonates and young infants (Figure and Video 4-1). This system has the capability of simulating real-time scanning from all acoustic windows. It offers the capability of performing 2D imaging, color flow and spectral Doppler, and M-mode modalities. From each infant, four-dimensional (4D) image volumes (3D plus real-time motion) were recorded using Philips IE33 echocardiograph. Up to seven 4D volume datasets were acquired from each infant, and at the same time, 2D video clips of color flow, spectral Doppler, and M-mode were recorded in standard echocardiographic views using five transthoracic echocardiographic acoustic windows (right and left parasternal, apical, subcostal, and suprasternal).

We employed a modified neonatal mannequin, a laptop computer, and an integrated electromagnetic tracking device including a magnetic transmitter and a 6 degrees of freedom (6DOF) sensor incorporated into a dummy transducer for this purpose. Four-dimensional volumes are sliced by invisible cutting planes controlled by roll, pitch, and yaw of the 6DOF sensor incorporated into the dummy transducer, resulting in a continuous real-time display of 2D echocardiographic images, which are shown on the main section of the display window. The location and motion of the cutting planes are duplicated on the fan-shaped cutting planes of the 3D heart displayed on the side section of the display window. A small arrow on the side of the cutting plane indicates the direction of the marker on the transducer (Figure 4-2). The coordinates from 27 specific slices of 3D image volume sets from the five echocardiographic windows are used to initiate the display of video clips of associated color flow Doppler, spectral Doppler, or M-mode, which are recorded and stored at the time of the original 4D volume acquisition.

For each infant, seven 4D DICOM echocardiographic volumes were virtually placed and oriented in their respective five echocardiographic acoustic windows on the doll mannequin. The location of each window is specific to each infant according to the variation in the acoustic windows encountered in the clinical setting. The 4D volumes are arranged so that one 4D volume is placed each at the left and right parasternal windows and one at the apex, two at the subcostal window for imaging the heart and abdominal great vessels and two volumes are placed in the suprasternal windows for imaging the heart and the head and neck vessels. The use of multiple volumes allows for the complete range of 2D imaging from each window.

VNETS as a Training Echocardiographic Simulator

Because the simulator was designed for hands-on training purposes, it can simulate actual echocardiography, including image acquisition by the manipulation of the transducer in the standard acoustic windows. All essential echocardiographic modalities can be simulated, including 2D, color and spectral Doppler, and M-mode imaging, along with hemodynamic measurements and report generation (Figure and Video 4-1). The simulator can be used for different levels of training. The beginner and intermediate levels would involve 12 to 17 sector cuts from all cardiac windows and would be appropriate in the training of physicians for point-of-care echocardiography. Pediatric echocardiography technologists and trainees in pediatric cardiology, on the other hand, may be required to master all 27 cuts (Table 4-1). Images for each window can be obtained by paying special attention to the orientation of the cutting planes of the 3D model of the heart displayed on the side screen, along with the image of 2D echocardiogram on the main screen of the monitor.