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February 4 , 2008

3-D Ultrasound — Volumetric Acquisition Provides More Data in Less Time
By Annie Macios
For The Record
Vol. 20 No. 3 P. 24

While 3-D ultrasound is common in prenatal imaging and screening, its use for clinical applications beyond obstetrics is just beginning to increase. But what does 3-D imaging bring to the table that traditional 2-D ultrasound can’t? Sonographers, physicians, and patients alike are learning firsthand how valuable the technology is in many facets of healthcare delivery.

Among its obvious benefits is that physicians gain a better picture—literally—of what they are looking at. With 3-D ultrasound, or volume imaging, capturing data volumetrically allows reviews from any plane. As such, the technology can be applied to clinical areas beyond obstetrics for more complete and accurate diagnoses.

In addition, data from the ultrasound exams can now be saved, reviewed, or retrieved at a later time since the information is digitally stored as a volume. This has positive implications for following a patient over a course of treatment or reducing the need to repeat the ultrasound exams if more angles of the affected area are needed, as with 2-D ultrasound.

Further, both sonographers and patients are pleased with the speed with which volume acquisitions are completed, and facilities using 3-D ultrasound can see the difference it makes in workflow.

Gaining Traction
“Volumetric imaging has been around for a long time,” says Terri Bresenham, vice president and general manager of global diagnostic ultrasound and IT for GE Healthcare. But actually making the 2-D acquisitions automated and using the volume to construct new views of anatomy or measurements true to geometrical form, she says, is how the technology has moved forward into 3-D.

Franklin N. Tessler, MD, CM, professor of radiology and chief of body imaging at the University of Alabama in Birmingham, is a strong proponent of 3-D ultrasound technology who has been working with Philips Medical Systems.

Compared with obstetrics, where it has been incorporated into protocols and long accepted for routine use, 3-D ultrasound has yet to gain traction in other clinical areas, according to Tessler, but it’s something he believes will begin to take hold as benefits of the technology become more widely known.

Richard Chiao of Siemens Medical Solutions agrees: “We believe 3-D will be the future of ultrasound for the simple reason of its user capabilities. It’s difficult to get consistency with 2-D ultrasound in capturing repeatable results, but 3-D provides a way to mitigate that.”

The availability of 3-D ultrasound has been one limiting factor of what Tessler feels is important technology. He likens it to the early days of color Doppler machines in the late ‘80s when a facility may have had only one color Doppler machine among the remaining grayscale machines, and patients would be shifted to the color machine based on their case and need. Tessler says that facilities are generally still in that stage with 3-D, with many having one to three 3-D machines to complement their remaining six to ten 2-D machines. “So for now, 3-D is used selectively,” adds Tessler.

In selecting who will be scanned using the 3-D machine, Tessler says it’s important to take into account such things as whether the patient has already had 3-D imaging or a case shows a need for more in-depth pictures. “Sometimes, a patient is done on a conventional machine, but various circumstances may necessitate looking at them on 3-D,” says Tessler.

With selective use, Tessler says the best exams to employ 3-D technology include any areas surrounded by fluid, as it provides an excellent contrast. An example is the bladder, which is surrounded or filled with fluid. “We can see masses on the inner bladder walls with the 3-D ultrasound,” says Tessler.

Using 3-D technology can also show aspects of vascular anatomy that have previously been unseen. “With 2-D, we used to build a representation of the organ in our head based on what we saw in each individual view,” says Tessler. Now, with real-time 3-D images, he says doctors can appreciate what wasn’t available with 2-D.

“In vascular anatomy, it works well because the structures are large enough to view. For example, large vessels in an aortic dissection are better viewed in 3-D,” says Tessler. “You can tell what you’re looking at on a 2-D ultrasound, but with 3-D, it is much clearer to me and other physicians because we can rotate the view to see what we previously had to build mentally,” he adds.

One big challenge for ultrasound centers has been scheduling patients as soon as possible. With 2-D ultrasound, the manual “point-and-click” pictures that a sonographer must take can be time-consuming, often necessitating scheduling patients for a minimum of 30-minute blocks of time. Because 3-D ultrasound performs the same task in one half of the time or less and with better, more comprehensive images, workflow can be improved tremendously.

Kathy Sanguinetti, RDMS, RVT, ultrasound administrator with Radiologic Associates of Sacramento (Calif.) Medical Group, Inc., saw an immediate improvement in workflow and the number of patients the practice can image after purchasing five GE Healthcare machines in the spring. “It’s always been a challenge to accommodate patients in a timely manner. Usually it would take two weeks for a patient to get an appointment but often, as in the radiology field, you need tests sooner,” says Sanguinetti.

“Once we went to the 3-D machines, it took only five weeks to get the backlog down. Now, it only takes roughly two to three days to get in for an ultrasound,” she adds. Sanguinetti credits the sonographers for making that happen. “Once they got momentum, they didn’t want to stop,” she says.

For example, when previously doing a transvaginal ultrasound with the 2-D machines, the probe was inserted for approximately 10 to 15 minutes, and the sonographer would freeze the frame and print each picture one by one. Now, with volume imaging, the probe is inserted and pointed to the appropriate area, and the ultrasound sweeps through the organ manually or automatically to take the images.

Sanguinetti notes that it’s easier to schedule someone at the last minute knowing that a volume acquisition is being done because, rather than having to find a minimum 30-minute slot in the schedule, a 15-minute slot is all that may be needed and is much easier to accommodate.

“Not everyone is a candidate for 3-D, however. The 3-D volume acquisition is only as good as the 2-D image. A bad 2-D image will not be better on a 3-D image,” says Sanguinetti.

More Than Just an Image
When developing its 3-D ultrasound technology, GE Healthcare realized that volume acquisition alone held tremendous information, but it was just one piece of the puzzle. “We realized it must be an integrated system that not only provides improved ease and workflow, but that it also has to include a way to transfer the information easily,” says Bresenham. Therefore, their systems were redesigned to bring raw data capability to the ultrasound technology. “So when the volume information is sent to the PACS [picture archiving and communication systems], raw data goes along with it,” adds Bresenham.

At Radiologic Associates, once the 3-D ultrasound is completed, the volume information is sent to an independent workstation where an experienced sonographer extracts essentials such as pathology, single photos, and other representative information. These are sent to a radiologist via PACS. The radiologist can also do a virtual rescan by scrolling through the volume acquisition information or reviewing it over the sonographer’s shoulder, which also reduces physician time. The advantage is that patients usually don’t have to be called back, and the 3-D data provide more diagnostic material for the doctors.

“We’re getting more than we’ve ever gotten before. Diagnostically, it’s giving us a lot more information,” says Sanguinetti. By integrating IT solutions with the diagnostic information, Bresenham agrees that it puts all the pieces of the puzzle together in a beneficial way.

Sonographers are also pleased with the ease of use that 3-D ultrasound offers them, especially in light of repetitive stress injuries that they experience due simply to the nature of 2-D ultrasound.

“Most strain is caused when documenting a case, where sonographers would have to push in on the probe to get each image,” says Bresenham. With the volumetric approach, they can collect the shots and proceed to a workstation to manipulate the images and complete documentation.

“The sonographers love it,” says Sanguinetti, explaining that rather than holding a probe for 20 to 30 minutes at a time to capture each image separately for an exam, the time has been reduced to roughly 10 minutes to do volume acquisitions. “It’s changed the way we do ultrasound. I don’t see us ever turning back,” says Sanguinetti.

Future Opportunities
With the broad range of 3-D probes available, Bresenham foresees a variety of applications for 3-D ultrasound. “We’re excited about growing well beyond the initial applications of obstetrics and cardiovascular applications,” she says, while pointing out the technology’s potential in oncology; interventional medicine; vascular, musculoskeletal, and small parts imaging; and expanded use in the gynecological arena.

Tessler sees potential in using 3-D ultrasound in the areas of biopsies and radiofrequency ablation (RFA). For biopsies, he explains, 2-D usually suffices when positioning the point of a needle in a lesion. However, if the lesion is close to an interface that you don’t want to transgress, you must alternate between various perspectives until proper positioning is achieved. With 3-D, one can effectively view multiple planes simultaneously, and positioning can be done more rapidly.

In RFA, the doctor tries to position the tip of the probe and look at more than one point at a time. 3-D ultrasound enables the physician to see, literally, the “whole picture,” but he adds, “it may take a few years to gain traction as 3-D becomes more pervasive.”

Chiao also mentions echocardiology as an area where 3-D ultrasound can be applied with great success. “In this field, there is a need to look at complex geometry and to make measurements, and this kind of work suits 3-D very well,” he says.

Looking Ahead
The acceptance and increased use of 3-D ultrasound “will ultimately be driven by improved clinician workflow, as well as patient benefits,” according to Chiao. “Technology will naturally be drawn in this direction.”

“This technology is so fluid, it’s changed a lot over the last year,” says Tessler. “It holds a lot of promise, and it’s really fun to play with and explore the technology.” He also mentions that in recent years, it has been more difficult to generate enthusiasm among radiology about ultrasound, but 3-D ultrasound has sparked some renewed interest.

In developing their technology, providers of 3-D ultrasound are constantly looking for ways to improve their products. “We are developing into 3-D from several different directions, including decreasing user entry variability, increasing workflow, and finding new applications that will improve patient care,” says Chiao.

“It’s unusual to get a benefit for all key stakeholders,” says Bresenham, but she asserts that 3-D ultrasound seems to achieve that: for patients in reducing imaging time, for sonographers in providing the ability to interact more with patients and ergonomic benefits, and for physicians who now have more comprehensive data to make clinical decisions.

“It’s a technology that really makes sense to take a look at,” she adds.

— Annie Macios is a freelance medical writer based in Doylestown, Pa.