Two-dimensional ultrasound is arguably the most widely used diagnostic imaging modality, in large part due to the comparatively low price-point of the systems as well as its real-time, interactive acquisition capabilities. However, 2D imaging does limit the amount of information capable of being extracted from the image data. Three-dimensional ultrasound has been demonstrated to provide better qualitative and quantitative data for diagnosing physicians; but these systems come at a higher cost than their 2D brethren, which can limit their deployment.
A team from the Multimedia University, Cyberjava, in Selangor, Malaysia, has developed a method of creating 3D ultrasound images using a 2D ultrasound probe with a conventional digital camera. Their technique, described in the December issue of the Journal of Digital Imaging, holds the promise to allow clinicians in cash-strapped practices to conduct modified 3D ultrasound exams with their current equipment.
“Three-dimensional ultrasound offers the medical practitioners a view of slices through the human body, which is not possible using the conventional 2-dimensional ultrasound system,” wrote the authors. “In addition, the reconstruction of the 3-dimensional view reduces scanning and study time by the physicians, as the reconstructed 3-dimensional image allows the physician to manipulate the images and observe various parts of it without requiring further scanning, thus reducing patient waiting time and discomfort.”
The technique involves using a calibrated digital camera to identify the position of the ultrasound probe in relation to the camera. The probe is then calibrated to deduce its position in relation to the ultrasound scan. From this data, position information can be extracted and tagged to the respective scan.
This information is then loaded into a 3D ultrasound software application, STRADX, developed at the University of Cambridge in England. Although the software was created for freehand 3D ultrasound acquisition using a 2D system with an optical or magnetic tracking system for probe localization, the Malaysia researchers reported that it worked well with their setup.
“By supplying a set of 2-dimensional ultrasound B-scans, together with the precise position of the probe while scanning, software such as STRADX could be used to enable 3-dimensional ultrasound imaging,” they wrote.
The team reported that by replacing an optical or magnetic tracking system with a calibrated camera, the overall cost of a 3D ultrasound system based on STRADX was significantly reduced. The $700 cost of their proposed system, which used a Ricoh RDC i500 digital camera, is almost a seventh of the price of a magnetic tracking system.
“This solution allows for a better result from existing 2-dimensional ultrasound equipment, and is feasible for use by establishments that are unable to opt for newer, more costly, methods of acquiring better quality 3-dimensional ultrasound imaging,” the developers wrote. “The 3-dimensional tracking technique by applying camera calibration can also be used for other, nonmedical applications.”