DSPs advance medical imaging

By: 
June 09, 1997

Just 20 years ago, physicians still relied on surgery to determine the cause or extent of a patient's illness. These days, doctors manipulate computed tomography, magnetic resonance imaging, and ultrasound machines instead of a scalpel. "Slicing," happily, now refers to the non-invasive creation of 2-D images.

Much of the credit for this advancement in medical diagnostic procedures belongs to the tiny chips called digital signal processors, or DSPs. Developed as a fast alternative to microprocessors, DSPs serve as a basic building block to all medical imaging technologies. The steadily increasing computing power, speed, and functionality of DSPs, moreover, help reduce part count, contributing to a net savings in system size, cost, and power.

"Digital signal processors help medical equipment manufacturers meet the opposing goals of higher performance and cost containment," states Ray Stata, CEO of Analog Devices, Norwood, MA. "Even as system complexity within medical equipment is increasing, so is the functionality of the ICs. Many mechanical and passive electric circuit functions are now integrated into the signal processing component."

These architectures, combined with extremely fast computational capability, have helped pave the way for advanced imaging applications such as virtual endoscopy, which substitutes CT and MRI for conventional endoscopes. Ultrasound technology, in particular, has benefited from DSPs because of its need to process great quantities of data in real time.

Programmable ultrasound imaging. Consider, for example, SieScape imaging--a breakthrough ultrasound diagnostic application recently introduced by the Ultrasound Group of Siemens Medical Systems, Issaquah, WA. Able to increase the field of view in ultrasound by displaying panoramic pictures of internal organs and their surroundings, SieScape imaging technology relies on a new-generation signal processing chip.

Developed by Texas Instruments, Dallas, the TI C-80 MVP--for multi-media video processor--manipulates video data extremely fast. "There are two TI C-80s on our board," explains Pat von Behren, director of advanced development, Siemens Ultrasound. "Between them, they are capable of 4 billion operations per second."

By dividing 100 mHz into 4 billion, von Behren equates the C-80's total speed to 40 Pentium processors. "If you look at the DSP's block diagram," he says, "it has four parallel processors and one RISC processor. So you can really make the programs fly."

Sheer speed, however, is only part of the processor's appeal; programmability is the other selling point. Indeed, it was this capability that allowed development of the Siemens SieScape imaging technology.

Historically, ultrasound imaging systems have been designed from single-purpose hardware components. Programmable devices simply did not have the speed to keep up with the ultrasound data stream. Consequently, major advancements in conventional ultrasound systems required reinvention of the dedicated hardware--a time-consuming and costly process.

Availability of a programmable DSP, claims von Behren, "allowed us to shorten our development time. Rather than building a new board, we program a new algorithm."

Panoramic images. How will Siemens' SieScape technology affect the medical imaging industry? Because it combines real-time scanning, previously restricted to very narrow fields of view, with the ability to present a very large picture, physicians can view both the target organ and its surroundings to make a diagnosis more rapidly and with greater confidence. Clinical evaluators have also said that the large anatomical views provided by SieScape imaging improve communication and understanding between physicians and patients.

Siemens Ultrasound Group Vice President Lothar Koob predicts that SieScape imaging is the first of many future applications that will emerge because of new-generation, programmable DSPs. Anticipated turn-around time for new ultrasound applications, he believes, will reduce the industry average of 18 months to less than 6 months.

"We're going to see more and more power in these sorts of chips that are programmable," adds von Behren. "As a result, the clinical community will see new applications more quickly."

Other DSP advances will ultimately benefit the clinical community as well. For example, Paul Errico, medical instrumentation marketing manager at Analog Devices, points to the company's new SharcTM family of floating point DSPs. Its claim to fame: on-board memory which contributes to extremely high performance.

"One of the limiting factors with DSPs has been the ability to get data off the chip and into RAM," Errico explains. "Even though the DSP processes data very quickly, there have been delays associated with storing data."

By designing the SharcTM family with cache memory, Analog Devices can circumvent storage delays. The result of DSP advances such as programmability and increased computational power--whether applied to ultrasound, MRI, or CT--can mean only one thing: Faster, clearer, and sharper medical images for early detection, better diagnosis, and improved health care.


Other applications

  • Arcade games

  • Modems

  • Set top boxes

  • Video processing


Fine-tuned for speed

While a microprocessor is general purpose by nature--performing multiple functions such as mathematics, I/O, interfaces--digital signal processors are designed for raw computation only, at very high processing rates. Analog Device's ADSP 21061-SHARC, for example, is a complete signal processing system on a chip. SHARC processors add a large dual-ported SRAM, a host port, multiprocessing capabilities, link ports, serial ports, and an independent I/O processor to the 32-bit floating-point core. Result: Superior processing of high-fidelity audio, speech, image, and full-motion video signals.

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