Diasonics builds on VST scanner performance

Diasonics will unveil a significant advance in its ultrasoundproduct line this month at a meeting of about 150 physicians andsonographers in San Francisco. The VST Masters Series scanneris an upgrade to Diasonics' existing Spectra VST (for variablesummation technology), introduced a year ago (SCAN 4/8/92).

The Milpitas, CA, vendor hopes to demonstrate that its initialdisplay of R&D prowess with the development of VST was nota flash in the pan and that users can depend on routine upgrades.Diasonics will drop the name Spectra with the new Masters Seriesbut keep the term VST, which executives believe has become associatedwith high performance.

A new feature provided by the Master Series upgrade is labeledultrasound angiography. Unlike traditional color Doppler techniques,ultrasound angiography does not depict velocity or directionaldata. Instead, it creates a vascular flow profile similar to whatis seen with x-ray and MR angiography, according to the company.

Additionally, several improvements have been made in existingVST capabilities, including:

• increased gray-scale resolution;

• patient-specific imaging that allows the user to matchmachine parameters to patient body type;

• color-flow enhancements;

• an improved user interface; and

• a broader family of Matched Impedance transducers.

The system and upgrade should be commercially available thissummer. Pricing of the field upgrade and new system has not yetbeen determined.

Among the enhancements to the system's core technology is animproved version of confocal imaging. 2D Confocal provides a two-foldimprovement in resolution, the company claims. The system willprovide adequate resolution for abdominal and small-parts imagingat 15 frames per second and for obstetric and vascular applicationsat 25 frames per second.

"We have increased the frame rate while keeping the resolution,"said Omar Ishrak, Ph.D., Diasonics vice president of product development.

The operator will have the option of running at a slower framerate if higher resolution is needed, Ishrak said.

"Some doctors are connoisseurs of image quality, willingto put up with a slightly lower frame rate for better resolution.This provides them with the opportunity to obtain this betterresolution."

Patient-specific imaging allows the operator to classify thepatient into one of three types: light, medium or heavy. Pushingthe button on the console for a light or thin patient optimizesthe near field. Pushing the button for a heavy patient optimizesfar-field imaging.

"Operators can do with a single probe those proceduresthat they used to do with perhaps three probes," Ishrak said.

The decision to emphasize near- or far-field scanning on mostmachines is made through the choice of probes or, more exactly,the choice of frequencies--lower for far-field imaging and higherfor near-field, Ishrak explained.

"Operators do not have to be experts in ultrasound toget very good results (with the V.S.T. Masters Series), and theywill not be forced to always pick the right transducer since onetransducer can do the tasks of several," he said.

Although frequency is one parameter that is changed when switchingfrom light to heavy settings, it is not always the dominant parameter,Ishrak said.

"There are other settings, like the aperture sizes andthe spacing between the zones in confocal imaging that changeaccording to the type of patient," he said.

Patient-specific imaging is different from Acuson's MultiHertz,which optimizes the transducer frequency to body type. Instead,the Diasonics feature reconfigures multiple confocal parametersto optimize performance for particular body types.

Patient-specific TruColor processing improves color in theMasters Series. In order to concentrate on Doppler signals returningfrom blood and not from other tissue, system parameters in thecolor processor are dynamically altered according to the tissuethe signal has bounced off. This change occurs on a pixel-by-pixeland frame-by-frame basis, thereby maximizing sensitivity and temporalresolution, while minimizing flash artifact, Ishrak said.

Another upgrade in the Masters Series is the FastScan Interface.Feedback from clinical investigators and a time-in-motion studyconducted by the company led to the new interface, which groupsthe controls in order to optimize patient throughput, reduce trainingtime and optimize the number of keystrokes.

Enhanced image quality and color will allow users to see vesselsand objects with the new VST that they would otherwise have missed,Ishrak said.

BRIEFLY NOTED:

• Shimadzu Medical Systems has hired Mark Silverman to headup a new MRI division, effective this month. Silverman, formerexecutive vice president and general manager of Hitachi AmericaMedical Systems, was instrumental in Hitachi's successful introductionof low- and mid-field permanent magnet MRI systems into the U.S.market (SCAN 10/24/90).