Duke Engineers Unveil New 3-D Ultrasound Technology

April 29, 1996

DURHAM, N.C. -- A new imaging technology pioneered at Duke University will allow physicians to study a living internal organ's entire volume just as though doctors had a window into their patient's body.

This three-dimensional ultrasound process uses a novel parallel computing technique to instantly analyze a myriad of reflected sound waves, creating images so quickly that clinicians can view a whole human heart even as it is beating.

But because studying an entire organ at once can be confusing, doctors are also able to electronically "dissect" and remove selected slices of medical interest and display them on a computer screen, one of its inventors said in an interview.

"It makes current ultrasound technology obsolete," said Olaf von Ramm, a Duke professor of biomedical engineering who also spearheaded the development of real-time, two-dimensional ultrasound technology now used in hospitals around the world.

"Physicians can look at the front of the heart, the side of the heart, and a cross section of the heart simultaneously, all on the fly," said von Ramm, who is director of the National Science Foundation Engineering Research Center (ERC) for Emerging Cardiovascular Technologies, based at Duke.

The ERC receives $2.4 million a year from the National Science Foundation and about $5 million annually in other public and private support to fund engineering research directed toward the heart and circulatory system. Besides being its director, von Ramm also heads the ERC's 3-D ultrasound research program, which has itself received about $3 million in funding.

A technology perhaps best known for identifying the gender of fetuses in the womb, medical diagnostic ultrasound uses a hand-held electronic wand to bounce high frequency sound waves off hidden anatomical features under the skin. The returning sound waves are then processed electronically to create pictures of the body's interior.

While those pictures are not always as sharp as in other body imaging technologies, ultrasound has some advantages. Unlike a computerized axial tomography (CAT) scan, it uses no X-rays. And unlike magnetic resonance imaging (MRI), it does not require a powerful magnetic field.

"It's like yelling into the body at a very high pitch," von Ramm said. "Ultrasound is always a very nice first diagnostic technique, because it is non-invasive and relatively inexpensive."

Von Ramm has studied ultrasound since coming to Duke in 1971 for his Ph.D. He holds three patents and did much to develop the "phased-array" 2-D ultrasound systems that are a standard in hospitals around the world. Phased-array ultrasound works in a similar way to military phased-array radar, which uses electronic circuitry instead of a rotating dish to aim and focus signals.

But 2-D ultrasound has a big limitation: it can scan only a small thickness of the body at one time, von Ramm said. "With 3-D ultrasound we can scan an entire volume. We can scan an entire beating heart very rapidly, and look at any part of it that we choose.

"All other imaging technologies that are out there, including magnetic resonance imaging and computerized tomography, require seconds to build up an image of the heart. Since the heart moves, that makes the image blurred."

The 3-D ultrasound technology being developed at Duke uses an advanced phased-array

concept known as "Eploso-Scan."

Hundreds of ceramic sand grain-sized crystals located on the wand emit simultaneous high frequency sound pulses so that an entire volume of space is swept with sound simultaneously. Hundreds of other crystals then receive the returning echoes, which are converted and processed into digital pictures using advanced microelectronic circuitry.

In order to capture an image of a beating heart or a moving fetus in "real time," meaning with no delay, each signal must be processed at the same time using a higher order computation technique known as "massively parallel" processing.

Engineers at the Duke ERC have been working on 3-D ultrasound since 1987, but von Ramm secured the first of two patents on the idea in 1985. He said he and Stephen Smith, a Duke associate professor of biomedical engineering, actually originated the idea in response to the 1980 crash of an Air Florida jet into the Potomac River at Washington.

The pair originally envisioned incorporating such a technology into an underwater camera that rescue workers could use to find accident victims in murky water. But the research was quickly diverted toward medical applications, he said.

He, Smith, and John Oxall, another engineer with business experience, have also founded a small startup firm named 3-D Ultrasound Inc. in downtown Durham to develop commercial versions of the original Duke experimental device, which is about the size of two large refrigerators. Oxall serves as the firm's president. Recently, 3-D Ultrasound donated a more-compact experimental unit -- about the size of a commercial 2-D ultrasound machine -- to the Duke Medical Center for early evaluations.

As with all diagnostic ultrasound devices, operators first apply a special jelly to provide the electronic wand a good acoustical contact with the bare skin. The wand is then moved over a patient's chest or abdomen until the internal feature of interest appears on the viewing screen.

By using a touch pad, doctors can call up views of as many as 16 different slices of the heart or another organ at once. Slices can be at different angles. They can be made to be thicker or thinner. In addition to viewing them instantly, doctors can also store all the images for later followup analysis.

With two-dimensional ultrasound, physicians can only probe a space as thick as 2 millimeters (about 6 hundredths of an inch) at one time, said Dr. Barbara Carroll, a Duke Medical Center radiology professor who heads the Duke radiology department's ultrasound section.

"With this type of volumetric imaging, you can encompass a large area simultaneously, as opposed to having to spend a lot more time scanning through many, many millimeter-wide sections," she added. "The fact that it is actually acquiring these volumes in real-time is particularly nice for anything that is moving -- like a beating heart or a fetus in the amniotic fluid."

Carroll, who is von Ramm's wife, has tried the experimental 3-D ultrasound device on heart patients and obstetrical patients as well. At the time of a recent interview, she had also viewed one fetus in its mother's womb.

"My feeling is you should be able to do volumes of anything more accurately with this technique, whether it's a kidney or a tumor or any volume of that sort," she said. "The whole volume can be stored, so you can reproduce those planes again and again. You can just look through it to your heart's content.

"The technology is just in its infancy, but I think it will be really quite exciting. I think that in the future people are going to be doing more and more of this type of imaging. It gives you everything that the 2-D scan gives you and then some. The odds are that this will be the way that people are going to go."

Duke University

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