Turning Flat Images into Three-Dimensional Images
A three-dimensional ultrasound, known as 3DUS, is a new technology that creates images of the body to assist doctors in making a diagnosis. 3DUS has seen widespread use in obstectrics but is expanding to other fields as well, including cardiology, mammography and gynecology. The process directs high-frequency sound waves through a small sound amplifier (called a transducer) that is placed on the patient to reflect the sound waves. This reflected sound is collected and sent back to a computer that uses special software to create images. Doctors are then able to see a basic image of the fetus, the uterus or cervix of a woman, cysts or potential tumors in a breast, or the action of the human heart, to assist in making a diagnosis. The black and white images created by the system are not yet of high resolution, but the technology continues to improve.
Collecting Sound Waves
The 3DUS image is captured by a scanner. There are various models and sizes of scanners, and the model used depends on the type of image captured. Neonatal and mammography scanning typically uses hand-held scanners, while larger models allow a scan of the patient's heart. Sophisticated scanners include an integrated positioning system that helps the operator use the probe and a sensor. The scanner uses sound to collect a series of static images, allowing the medical practitioner to see the organ or tumor from various sides. For instance, a cardiologist looking at a heart will receive several views of the heart from different viewpoints. The more advanced scanners utilize faster sound speeds and are able to capture greater numbers of images. Less advanced scanners may not capture enough images for an accurate diagnosis, according to the 3-D Ultrasound Imaging Group of the Departments of Radiology, Pediatrics and Reproductive Medicine at the University of California in San Diego. Even a small number of interior views of the heart, cervix or fetus, allow doctors to discover valuable information to assist in making a diagnosis.
Displaying the Image
The ability to quickly collect large amounts of information and send it to the computer is critical for creating useful images. Scientists and computer software designers used optimized algorithms to recreate images from the sound waves collected. The process requires state of the art computers. Most of the equipment in use today collects only slices of the image, a process called "multiplanar imaging," as if a video camera was allowed only to capture every tenth frame to play back to the viewer. The software also utilizes a rendering program that integrates mathematics to establish the guidelines used to create the image, including capabilities to rotate the image using geometry. A "best guess" image is created using the math-based software. 3DUS operators do not need any advanced computer expertise. They need only a basic operating knowledge of the scanner and the computer.
Current State of Technology
While 3DUS technology continues to advance, current challenges in the use of 3DUS include accurately reading the three-dimensional image from a relatively small number of sound images. Scientists question the validity of the computer generated images. The University of California, San Diego scientists found that: "...ultrasound data pose a major analysis challenge...of how acoustic images are formed." In evaluating the first clinical use of three-dimensional breast ultrasounds, a team of doctors reported in the European Journal of Radiology that the scans were "a promising diagnostic adjunct to mammography," but they concluded that they could not be substituted for the current imaging.
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