GE releases annual ultrasound upgrade with focus on gray-scale imaging

New technique forms digital ultrasound waves

GE Medical Systems this month introduced its latest upgrade package forthe high-end Logiq 700 MR ultrasound scanner. GE claims that thepackage, called Digitally Encoded Ultrasound, represents a new level ofdigital ultrasound beamforming that results in sharply improvedgray-scale image quality, especially in the far field.

The roll-out ofDigitally Encoded Ultrasound is part of GE’s strategy ofintroducing one “breakthrough” technology a year inultrasound, first for Logiq 700 MR, and then migrating it to lowerprice-points in GE’s product line. GE hopes the strategy will helpthe company earn a reputation as a technological innovator that can keeppace with dedicated ultrasound firms like Acuson and ATL.

DigitallyEncoded Ultrasound was designed to attack a common problem in ultrasoundimaging: In order to visualize structures deep in the body, sonographersmust use low-frequency probes, which have better penetration. Thedownside of low-frequency probes, however, is that they have poorerresolution than the high-frequency transducers used for near-fieldimaging.

In order to resolve this dilemma, GE engineers examined theway scanner beamformers create the sound waves that are transmitted intothe body, said Omar Ishrak, general manager of global ultrasound at GE.Typically, beamformers create analog sound waves that are transmitted,received, and then converted into digital signals. Digitally EncodedUltrasound, however, provides the base platform for a fundamentally newway of creating ultrasound beams, Ishrak said.

The highest level ofthe Digitally Encoded Ultrasound package is a technology called CodedExcitation, which creates sound waves that are coded as digital datarather than in analog form, Ishrak said. These digital beams aretransmitted into the body as a sequence of pulses rather than as soundwaves, and the returning pulses are decoded by the beamformer as aseries of zeros and ones.

“You can send a very long sequence ofones and zeros into the body. Because the sequence is long, there ismore energy, and it goes deep,” Ishrak said. “The series ofcodes represents a certain frequency, and that frequency is arbitrary.It can be very high, and high-frequency information can reach the backof the liver, for example.”

As a result of the digital codes,Coded Excitation provides high resolution deep into the far field,Ishrak said. The technique enables users to achieve the resolution of a7-MHz probe at depths commonly reserved for 3-MHz probes, such as at 18cm. Coded Excitation is particularly useful for large,difficult-to-image patients.

Automatic Tissue Optimization is anothercomponent of the new upgrade package. It is a technique by which Logiq700 MR automatically adjusts gray-scale imaging parameters to achievethe best image quality for the type of tissue being imaged, Ishrak said.The technique can help lessen the impact of operator variability onultrasound studies.

Digitally Encoded Ultrasound also bringsimprovements in Logiq 700 MR’s ability to conduct 3-D imaging andtissue harmonics. Logiq 700 MR scanners with the upgrade are now able torotate and reslice 3-D images, and a technique GE calls Image Scalpelenables users to remove obscuring structures and layers of tissue from3-D images to focus on a particular organ of interest.

DigitallyEncoded Ultrasound builds on the Voxel Image Processor (VIP) upgradereleased for Logiq 700 MR a year ago (SCAN 5/14/97), and users inthe field who wish to upgrade must have the VIP package. DigitallyEncoded Ultrasound includes hardware and software changes and will costin the range of $60,000 if all levels of the package are purchased. Anew Logiq 700 MR with Digitally Encoded Ultrasound will run about$250,000, which does not represent a price increase over a Logiq 700 MRsystem with the VIP package.

GE believes that the new technologies, inparticular Coded Excitation, represent an entirely new level of digitalultrasound technology, much in the same way that digital beamformersrepresented an advance over analog beamformers when first introduced inthe late 1980s. Whether the technology is truly a breakthrough islargely up to the clinical community to decide, but GE believes thatDigitally Encoded Ultrasound will have more of an impact on ultrasoundimage quality than the VIP upgrade, which was highly touted by thecompany last year.

One clinician believes that GE has a winner on itshands. Dr. Philip Ralls, a professor of radiology at the University ofSouthern California, has worked with the Digitally Encoded Ultrasoundpackage for the past month and is impressed by itscapabilities.

“What we’re seeing here is a significantadvance that is quite visible in the images,” Ralls said.“This enhances the overall gray-scale image quality, one of themost significant things that you can do. Gray-scale imaging is tough todo properly, and a visible advance such as this will translate intobetter diagnoses.”