Wireless technology gets radiology unplugged

By: Douglas Page

Radiologists generally make the shift from light boxes to PACS with less psychological trauma than do referring physicians, many of whom squirm at the notion of no longer being able to hand-carry images anywhere and view them wherever they find a light source.

Whether clinicians view images on expensive PACS workstations or simple PC monitors, the number of viewing screens in a hospital is limited, and they never seem to be located where the physician happens to be at the moment. The answer to this digital anxiety may lie in wireless technologies, which give clinicians the same freedom to prowl hospital corridors as in the good old days of screen-film.

But no longer will they have to hold a film-based image up to the nearest ceiling light, according to Dr. Paul Chang, director of radiology informatics at the University of Pittsburgh Medical Center.

"Clinicians hate getting up from lunch to go find a workstation to view an image," Chang told a Society for Computer Applications in Radiology University "graduate" class at the society's meeting in May. "The current interest in personal mobile computing devices such as personal digital assistants and data tablets reflects the demand for a more mobile solution for information delivery and access."

Wireless networking, which is attractive where the desire to roam is strong and the installation of a cable or fiber infrastructure is impractical or too expensive, is the enabling technology for mobile computing. With wireless networking, users can establish personal area networks (PANs) connecting a variety of devices, including PDAs, pagers, cell phones, printers, and headphones.

Wireless technologies transmit data via radio wave instead of shooting electronic bits down copper wire or optical fiber. In a typical configuration, a radio transmitter/receiver (called a transceiver or access point) is connected to a traditional wired network. Client devices such as PDAs, data tablets, and laptops talk to the access point using a tiny transceiver imbedded in the device or attached to it in the form of a PC card, compact flash, USB (universal serial bus), or PCI (peripheral component interconnect) interface. A number of client devices can communicate simultaneously with a single access point. Wireless clients located within a single campus can thus operate like regular wired devices in conventional networks.

Wireless technology is available in three forms: infrared, microwave, and radio wave. Infrared is used over short, line-of-sight distances, mostly to facilitate communication between PDAs, laptops, and printers. Microwave (18 to 31 GHz) provides relatively high bandwidth performance in both terrestrial and satellite applications. Microwaves, however, are sensitive to rain and snow, and satellite links suffer from delays of up to 600 msec, which can be a significant disadvantage, according to Chang. New low-earth and middle-earth orbiting satellites may provide solutions to the latency problem. Radio wave (2.4 to 5 GHz) is the most popular choice for wireless broadband local area networks (LANs) and PANs like those now emerging in some hospitals.

After many years of proprietary products and ineffective standards, the networking industry has finally settled on one set of standards for wireless networking: the 802.11 series from the Institute of Electrical and Electronics Engineers. These standards, which define wireless Ethernet, or wireless LAN, have several disaccordant iterations (802.11b, 802.11a, and 802.11g are currently pertinent to U.S. markets), each with unique advantages and disadvantages.

• 802.11b. This standard (so-called Wi-Fi, 2.45 GHz, 11 Mbps theoretical bandwidth, maximum distance about 300 feet) is by far the most popular wireless LAN offering. Advantages are low cost, widespread vendor interoperability, and ample device support.

Disadvantages include the necessity for clients to share a single access point. The growing use of 2.4-GHz wireless phones and wireless Bluetooth devices could also crowd the radio spectrum within some facilities, substantially decreasing 802.11b LAN performance.

"Shared bandwidth, even at 11 Mbps, doesn't go very far," Chang said.

The new 802.11g draft specification, expected later this year with products available in 2003, has been offered as a solution. Also, the FCC in May approved changes in the rules governing spread-spectrum technologies used by fixed wireless operators, effectively freeing Bluetooth to perform collision avoidance between other radio systems and itself.

• 802.11a. Users should consider using 802.11a (5 GHz, 54 Mbps theoretical bandwidth, maximum distance 200 feet) if high performance is an issue, as when transmitting large images and files. The use of 802.11a operating in the 5-GHz band avoids much of the interference experienced by 802.11b LANs.

This standard has several disadvantages. It tends to be more expensive because the reduced range may require additional access points. Nevertheless, it is still a shared resource. Users of both 802.11a and 802.11b can expect maximum data throughput to be about half the theoretical bandwidth because all users on the LAN are sharing the same radio channel. The data rate decreases as the distance between the user and the radio access point increases.

Also, 802.11a is not backward-compatible with 802.11b. In Europe, regulators of the radio spectrum block the use of 802.11a products operating in the 5-GHz radio band, although this may change soon. Synad, a London engineering company, has announced the development of a dual 802.11a/b chip that will enable product developers to deliver wireless LAN radios that speak both 802.11a and 802.11b.

• 802.11g. The industry's first chip designed to support 802.11g (2.45 GHz, 54 Mbps theoretical bandwidth, range of 300+ feet) was announced last January and touted as the high-bandwidth alternative to 802.11b. It may help enterprises migrate from relatively slow 802.11b wireless LANs to faster nets while still operating in the same 2.4-GHz band.

This alphabet soup of competing technologies can be bewildering, especially for budget-minded hospital administrators.

"There is confusion about this topic for good reasons," said Bruce Brown, a PC Magazine and ExtremeTech.com editor. "A major concern is the surge in adoption of 802.11b wireless networking. The thought that 802.11b wireless technology might already be outdated with the introduction of 802.11a products is worrisome."

Incompatibility concerns between 802.11b and 802.11a are baseless, according to Brown. The two can work together easily and inexpensively, and products likely to appear on the market this year will make coexistence easier.

"Later this year several dual-mode products are slated for introduction that will act either as access points for, or bridges between, 802.11a and 802.11b wireless networks," he said.

Conflicting technologies haven't dampened interest in wireless networking. IT consulting firm Gartner anticipates more than 10 million new wireless LAN PC users during 2002. Although most will be using the 802.11b standard, sales of 802.11a products are expected to increase rapidly in North America during the second half of 2002.

SECURITY CAVEAT

While wireless technology potentially offers many advantages over hardwired networks, users should be aware of its current level of security, which Chang calls "worthless." Security on all three 802.11 standards has been treated as little more than an afterthought. But a new standard, 802.11i, is part of a set of security measures that will attempt to address and overcome these issues by year-end.

Chang offers recommendations for security on wireless devices:

• Turn on the wireless equivalent privacy (WEP) feature.
• Don't use the "default" extended service set identifier, which identifies the access point of the wireless LAN.
• Put your access points in the middle of the area you want covered. This improves security and decreases interference. Bandwidth-hungry applications that require transfer of large data blocks-such as digital images-are not desirable. Use just-in-time mechanisms to deliver large multimedia objects.

MR. PAGE is a freelance writer in Redondo Beach, CA.