Diasonics VST upgrade works around 48 channels

Diasonics made several improvements in its Spectra high-end ultrasoundscanner as part of the variable summation technology (VST) upgradeannounced in March (SCAN 4/8/92 and 5/6/92). One thing did notchange, however: the vendor's use of a 48-channel front end originallylicensed from Acoustic Imaging.

Competing vendors with more channels in their premium systemspoint out that lateral resolution improves with the number ofchannels used. With fewer channels, an ultrasound system requiresfewer lines to scan a particular field- of-view, and thus hasthe potential for a faster frame rate or more transmit zones (withless sacrifice in frame rate).

Lateral image resolution, however, is a crucial competitivefactor among high-end ultrasound scanners.

"There is an ongoing race in the marketplace for optimizationof image quality. The fundamental issue Diasonics will have toaddress is how to get beyond the constraints of the 48 channelsand the analog front end," said Eugene A. Larson, executivevice president of ultrasound competitor ATL.

All companies in the high end of the market will be makingongoing and often subtle improvements in their beamforming technologyas part of this competitive race for image quality, he said.

"It is dangerous to take any piece of technology and focuson it as though it were a pivotal item in terms of clinical performance,"Larson told SCAN.

Diasonics acknowledges that more channels are an advantagein ultrasound, but there are other ways to improve the image.

"If we had more channels we could do more things,"said Bruce N. Moore, president of Diasonics' ultrasound division."But we decided to take a different approach than just addingchannels. We didn't copy the lead of others. It (VST) is a radicallydifferent approach to solve fundamental problems. If you try toplay catch-up and copy people, you will never catch up."

Diasonics made several technical advances that compensate forthe relatively few number of channels in Spectra, said Omar Ishrak,vice president of product development. For instance, the firmdesigned curved-array transducers, which can have a courser pitch(spacing between elements) because the beam does not have to besteered. With a courser pitch, fewer channels can result in thesame aperture size.

"If I had more channels, I could make this (Spectra VST)better, but I would not use (more channels) in the same way thatothers are," Ishrak told SCAN. "There are umpteen otherparameters that can be configured in a way that does not makethe number of channels a restriction for us in competition withpresent-day machines."

Diasonics' frequency domain imaging, which takes a middle roadbetween ATL's broadband technology and Acuson's dual-frequencymultihertz feature, is also a means to improve image quality usingthe existing 48 channels, he said.

"Our probes have a wider bandwidth because of the waywe do FDI. We optimize frequency for every depth along the image,and can effectively operate at higher frequencies than otherscan. To some extent, that makes up for the fewer number of channels,"Ishrak said.

IF THE VST UPGRADE REVEALS ANYTHING, it's that Diasonics did notwaste its $200 million windfall from the sale of its MRI divisionto Toshiba two and a half years ago (SCAN 12/13/89). Divestingitself of that glamorous but resource-draining business has apparentlypaid off in terms of funds and focus, helping the company regainits earlier technical strength in ultrasound.

"Diasonics has not focused on ultrasound since the beginningof the 1980s," Moore said. "Diasonics ultrasound isa very different company today than it was 10 or even three yearsago. We have an entirely new management team, have rebuilt thesales organization and have an ultrasound technical team thatis unmatched in the industry."

While other vendors note that application of composite transducertechnology has a widespread history in the industry, Diasonicsdid accomplish something significant in developing matched impedancetransducers on its own.

Matched impedance composite transducer technology, also a partof the VST upgrade, improves near-field haze in the image, thevendor said. Previously, Diasonics had used transducers manufacturedby Acoustic Imaging.

"This is not Acoustic Imaging (technology)," Mooresaid. "We designed it and are manufacturing it in our ownlab. We have our own proprietary process and use completely differentmaterials than were available on the outside."

One problem noted by physicians at Diasonics' March introductionof the VST upgrade in San Francisco is that Spectra's improvedcolor-flow Doppler system cannot function simultaneously withgray-scale confocal imaging. Diasonics is working to implementcolor and the confocal transmit focus feature at the same time,Ishrak said.

Color-flow Doppler requires a maximization of frame rate. Diasonicsis adjusting its confocal software to produce the transmit zoneconfiguration that works best with color, he said. Transmit zoneswill be reduced, but the vendor expects to obtain multizone transmitfocus with a sufficiently high frame rate to accommodate coloras well.

No system is a perfect imager, but physicians are impressedthat Diasonics has brought itself back to the cutting edge ofultrasound and improved its product significantly, said LarryHaimovitch, a San Francisco medical technology consultant.

"Diasonics clearly advanced its state of the art to thepoint where it is a much tougher competitor to ATL and Acuson,"Haimovitch said. "It is difficult to say who has the bestimages."

Many physicians who used Diasonics ten years ago in its earlierdays of ultrasound innovation expressed a desire to see the companyas a leader again.

"I was surprised," Haimovitch said. "I thoughtit (Diasonics) had exhausted every bit of good will it had. Therewas a certain nostalgia--a hope that this fallen angel could makea comeback."