How Does 4-D Ultrasound Work?
Ultrasound technology has become ubiquitous in American health care facilities over the past two decades. According to a report from the U.S. Department of Health and Human Services, even a small doctor's office can purchase a "pocket doppler" device for as little as $200. However, innovation at the high end of the ultrasound market has resulted in devices that can "see" through your body in four dimensions.
How the Titanic gave us modern medical ultrasound
After an unseen iceberg spur tore through the Titanic's hull, physicist Paul Langevin built a transducer capable of helping other large ships detecting submerged obstacles. Langevin's invention helped vessels uncover submarines during the first World War, but his work drew on decades of research into bats' use of echolocation. By the 1950s, Professor Ian Donald pioneered the use of ultrasound transducers to generate a two-dimensional image of masses below the skin's surface. To this day, the International Society of Ultrasound in Obstetrics and Gynecology awards the annual Ian Donald Gold Medal to modern medical technology pioneers.
How ultrasound works
During an ultrasound procedure, the handheld transducer sends sound pulses through your skin. Differences between fluid, soft tissue, and hard matter reflect some of those pulses back to the probe. Today's ultrasound systems can convert measurements of this piezoelectric effect into a visual representation of your body's inner workings. Basic two-dimensional systems can capture a limited field of view in real time, suitable for video recording or printing.
3-D ultrasound units take doctors into a new dimension
Even as ultrasound gained popularity among doctors, the unreliability of a two-dimensional image still left room for doubt when testing for serious health issues. Many 2-D scans could rule out the most urgent problems, but still required doctors to run invasive tests. Three-dimensional ultrasound systems embed multiple 2-D transformers into a probe, generating enough data for a Central Processing Unit (CPU) to "stitch" together a static 3-D image. These tools generate directional data from the same kind of technology that tells your smartphone to rotate its display when you turn it.
What is 4-D ultrasound?
Although 3-D ultrasound scanners improved accuracy and resolution, static images robbed doctors of the ability to monitor real-time activity, such as muscle movement or blood flow. With the advent of high-speed, multitasking CPUs, today's most sophisticated systems can generate four-dimensional representations of what's happening inside your body.
Researchers prefer not to call these readouts "movies," although many doctors render video files of ultrasound scans for expectant parents. Using 4-D ultrasound systems, doctors can scroll forward and backward in time, while zooming and panning in all three spatial dimensions. Specialists can use different kinds of transducer arrays to generate alternate views of the body as well.
Government and private tests have shown no indication that the extra energy output by 4-D ultrasound systems causes any risk to patients. However, their relative scarcity means that you'll usually need to visit a dedicated clinic or ultrasound center to get a 4-D scan.
"How a 4-D ultrasound works," Dylan Kelly, eHow, 2013
"How ultrasound works," Craig Freudenrich, HowStuffWorks, 2013
"History of ultrasound and technological advances," Dr. Jim Tsung, Society of Ultrasound in Medical Education World Congress on Ultrasound in Medical Education, 2011
"Low-cost ultrasound equipment," Office of Inspector General, U.S. Department of Health and Human Services, 1991