ATL prepares introduction of first tomographic ultrasound system

SonoCT combines data from multiple angles simultaneously

Ultrasound images are inherently filled with artifacts that compromise image quality. A new technology, to be unveiled this week by ATL Ultrasound, promises to clean up these artifacts, providing a significant improvement in image quality. In the distant future, this technology might also pave the way for real-time 3-D imaging.

Dubbed SonoCT Real-Time Compound Imaging, this technology assembles tomographic images by sampling tissue from up to nine viewing angles or lines of sight. To achieve this, engineers changed the firing sequence of the transducer to fire several ultrasound beams, each electronically steered along a different angle. The reflected data is then compiled into a single compound image, which is updated in real-time.

The resulting image contains as much as nine times more information about the tissue than conventional imaging, according to ATL. When the beams are aimed within a single plane, the result is a dramatic reduction in artifacts that commonly degrade image quality. If the beams are focused into multiple planes, it is conceivable that a real-time 3-D image could be created.

ATL engineers are working on the development of this 3-D capability, according to chief technology officer Jacques Souquet. But the most immediate benefit from the technology, Souquet says, will come from the creation of single-plane tomographic images.

“A lot of what users have taken for granted as known natural artifacts of an ultrasound image either disappear or are greatly reduced (by SonoCT),” he said.

The system has been available to ATL luminaries for only a few weeks, but the consensus opinion is very positive, according to Souquet. Investigators have told ATL that the reduction in artifacts offers three primary benefits: increased diagnostic confidence, reduced dependence on the skill of the operator, and more reproducible results.

“You get much more complete information with SonoCT,” said Jim Brown, ATL’s senior director of clinical and technical marketing. “This is the first time we’ve been applying technologies similar to those found in CT and MR, where you have detectors and transmitters obtaining data about tissue from multiple lines of sight.”

The Bothell, WA-based subsidiary of Philips Medical Systems has been an innovator in ultrasound technology. ATL pioneered the development of high definition imaging (HDI) with the Ultramark 9 HDI in April 1991, as well as extensions of that technology, the HDI 3000 in October 1994, and the HDI 5000 in July 1997. ATL was one of the first to develop harmonic technology for both tissue and contrast imaging.

Its most recent development, SonoCT, will be sold as an option on the HDI 5000 and as an upgrade for the installed base of these units. Owners of HDI 3000 systems will have to upgrade to the HDI 5000 configuration if they want SonoCT. Pricing for SonoCT has not yet been determined, according to the company.

SonoCT will be part of a broader upgrade called Performance 2000. This upgrade package, as well as HDI 5000 units offering SonoCT, are expected to begin shipping in November. Among several other improvements in the Performance 2000 upgrade is ATL’s third-generation tissue harmonic imaging, as well as improvements in Broadband Flow Imaging, Color Power Angio Imaging, and DICOM connectivity on the HDI 5000.

SonoCT includes computer boards and patented algorithms specially designed for signal processing. Together they process the torrent of data generated by its use.

“We need this very high throughput in signal processing to process images in real-time,” said Brown. “Before now this was not possible. We would have had to stop, combine the image (from these different angles), and then start it up again.”

SonoCT cleans up artifacts resulting from speckle, clutter, noise, glint, dropout, and refractive shadows. By acquiring data at different angles, the random data indicative of artifacts can be digitally subtracted, while data indicative of real structures is accentuated. In so doing, image contrast and detail resolution are dramatically increased, allowing better differentiation of tissue, according to the company. Borders and interfaces are better delineated, which helps in localizing biopsy needles, Souquet notes.

“There is a tendency in ultrasound to lose track of the needle, because you’re not looking at the needle at the right angle,” he said. “Because we are compounding various angles (with SonoCT), the visualization of the needle is greatly, greatly enhanced.”

Initially, SonoCT will be possible only on high frequency linear array scanheads. This will limit its clinical utility to musculoskeletal, vascular, breast, small parts, and pediatric imaging. Engineers, however, are working to make the technology effective at lower frequencies.

“It’s primarily a matter of getting into the beamformer and doing multiple lines of sight with the scanhead, like curved arrays,” said Brown, who explains that SonoCT works best with larger aperture scanheads, such as those in high frequency linear arrays. “It’s very challenging to put SonoCT on other scanheads, but there’s a strong possibility that we’ll be able to do it.”

The clinical potential of the new technology has been documented in a range of cases. One luminary reports, for example, that during a breast exam SonoCT defined the capsule of a superficial fibroadenoma not clearly defined with conventional imaging. In another case, SonoCT delineated the lumen of the carotid artery and enhanced soft plaque borders, when conventional imaging had difficulty delineating even the lumen.

Marsha Neumyer, director of the Hershey Vascular Diagnostic Laboratory and assistant professor of surgery at Penn State University in Hershey, PA, said that the new technology allows a better evaluation of blood vessels.

“By taking the noise out, we can see plaque and pathology in the lumen of these vessels that we can’t see on other systems,” she said. “SonoCT has pushed us up to the next level. We’re no longer questioning what is in the vessels; we’re seeing it.”

This performance level was achieved only after ATL engineers overcame certain fundamental hurdles. One was rounding up available computational horsepower to handle the flow of information, which ATL executives say is nine times greater than the current flow from the HDI 5000 sans SonoCT. The extra computing power provided a foundation for SonoCT with its multiple beams of data. Advanced signal processing electronics compile the data into the appropriate geometry for display, updating the compound image in real-time as each new frame is acquired.

Once triggered with a single button push, SonoCT processing goes on automatically and transparently in the background. Operators have the option of switching to “survey” mode, which simultaneously fires just three ultrasound beams, thereby allowing structures to be scanned rapidly. Alternatively, “target” mode maximizes image quality by firing nine beams.

ATL plans to use SonoCT as a platform upon which to build further releases, the most intriguing of which may be real-time 3-D imaging. The biggest obstacle to overcome will be the acquisition and interpretation of data fast enough to present a real-time 3-D display.

“We’re getting closer and closer to that capability,” Brown said. “We’re building the computer power in the system to handle advanced technologies like that.”