Company drops analog-to-digital converter pricesIf you think the number of channels on cable and satellite TV has multiplied greatly over the last decade or two, you'll be impressed with the growth of imaging signal channels in ultrasound since
Company drops analog-to-digital converter prices
If you think the number of channels on cable and satellite TV has multiplied greatly over the last decade or two, you'll be impressed with the growth of imaging signal channels in ultrasound since the widespread adoption of digital beam forming (DBF) in the early 1990s. But what would have happened to the cable industry if your TV set required additional power for each new channel added on-or if the price went up proportionately to the number of channels? Would Ted Turner be where he is today?
That is the case in ultrasound. The more channels that are added to a system, the higher are its component costs and power requirements. Fortunately, market and technological forces are helping to balance out these component factors and raise the ceiling on channels for future ultrasound systems.
With high-end ultrasound systems exceeding 1000 signal channels, and even the lowest priced units packing 64 channels, a multiplier effect has increased the importance of component cost and performance within each channel. One of the most critical components within each ultrasound signal channel is the analog-to-digital converter (ADC). Happily, the price of ADCs is dropping substantially, while their power usage falls and their signal-to-noise and speed improve.
Burr-Brown, a Tucson-based integrated circuit (IC) developer and major supplier of IC components to the ultrasound industry, reported this month that it will sell its new 8-bit ADCs (ADS830 and ADS831) at a price of $3.95 per unit in batches of 1000, which is a one-third reduction in cost over existing technology. At the same time, these ADCs, built using customized complementary metal oxide semiconductor (CMOS) technology, will provide for lower power operation, higher signal-to-noise, and an analog-to-digital conversion rate of 60 to 80 MHz, according to Patrick Kirk, strategic marketing manager.
The 33% price reduction is a factor both of a general decline in CMOS prices and Burr-Brown's decision to trim its prices in order to encourage more ultrasound channel development and reap the benefits of economies of scale in ADC production, he said.
Ultrasound channel usage is increasing dramatically, both because of the growing number of scanners worldwide and the greater number of channel counts per system. Combined, these two factors will result in a 25% annual growth in the overall ultrasound channel count, Kirk said. A lower price for ADC technology should help boost volume in what is already expected to be the growth area of ultrasound: low-cost overseas markets in countries such as China and India, he said.
On the other hand, channel growth could be restricted in all segments of the market by the power requirements of ultrasound systems. Scanners plug into standard wall outlets at hospitals or run on batteries in a mobile configuration. All ultrasound systems have a power limit-or budget-under which they must stay. Unfortunately, components operating within each signal channel add to the power requirements of the system, Kirk said.
"If power dissipation stays the same, you are going to hit a wall in terms of how many channels you can come up with," he said. "So by lowering the power (usage), we allow our customers to increase their channel counts and still not exceed their power budget."
ADC speeds have risen over the years as equipment vendors pursued higher frequency applications of their systems, such as eye and skin imaging. It is not likely, though, that speed requirements will continue to rise dramatically, Kirk said.
"I have not been seeing any indications in the marketplace that greater than 60-MHz speeds are needed at the current time. Having said that, looking back three years, our customers didn't think any greater than 40 MHz would be needed, so stay tuned on that one," he said.
Higher resolution ADC technology is also being developed for ultrasound. Burr-Brown has developed a 12-bit ADC (ADS807), which has already been designed into the systems of several vendor customers, Kirk said. That higher signal-to-noise ADC was due for release in late June.
While ultrasound makes up a substantial share of the $300 million in sales that Burr-Brown records each year, the company also sells into other medical imaging modality markets, including CT and nuclear medicine, he said.
Channel counts are growing in CT, although the ADC speed requirements are not as high as in ultrasound. Channel counts in nuclear medicine are also increasing, while the ADC resolution requirement is rising from 8 bits to 10 bits, Kirk said. As with ultrasound, the greater number of channels in nuclear medicine is impacting power usage.
"There are interesting parallels in the gamma camera story," he said. "The channel counts there are increasing and so power dissipation must go down. It is the same basic driver as the ultrasound market."