Electromagnetic Fields Force Change in Health Care Design
November 2006 - Health Care Facilities
Going to the hospital isn’t what it used to be. Doctors use PDAs to communicate, patient information is shared wirelessly with nurse stations, and even the clocks can be wirelessly synchronized. It’s not just patients who feel the impact of technology. Today, hospital buildings are being designed with technology in mind. Chris Lake, senior associate at BSA Life Structures, cites a current hospital project to illustrate the degree to which technology is used in modern hospital design.
“We have two design team meetings for the project,” says Lake. “One team addresses the physical building design. The other team meets solely to address the various technologies that need to be accommodated within the design.”
Two of the biggest challenges facing hospital facility executives are managing the various wireless networks within their buildings, and appropriately shielding the multiple radio frequencies (RF), electronic, radiation and magnetic fields generated within a hospital.
In the last decade, hospitals have experienced an explosion of wireless technology. This includes patient-monitoring systems on a UHF frequency, emergency radio systems or facility maintenance radio systems on UHF and VHF frequencies, and local area networks (LAN) — popularly known as WiFi — which operate at 2.4 or 5.4 gigahertz. There are also ubiquitous cell phone signals, the PDAs that doctors and nurses use, and devices that inadvertently generate high-frequency transmissions, which range from microwave ovens to arc welders. Because these signals can interfere with one another, mastering the multiple RF networks within a hospital is essential.
“Simply put, hospitals are a sophisticated RF environment,” says Tony Whaley, principal at RTKL. “That didn’t use to be the case. A decade ago, it generally consisted only of UHF/VHF radio, and wireless paging.”
The amount of stainless steel in hospitals further complicates matters, causing spotty coverage, particularly for LANs. Dead areas and dropouts in network coverage can be caused by multipath propagation and signal attenuation within hospitals — both of which can become vitally important when critical patient is being shared information across a LAN.
“With any wireless technology, it’s important to consider the reception and interference for the various systems and frequencies that you’ll be using,” says Whaley. He recommends RF site surveys to determine RF fields.
Steve Juett, director of clinical programs for EQ International, agrees. Juett and Whaley both cite three questions that will help facility executives better control the wireless networks inside their hospitals:
- What are the frequencies of the wireless systems used by the hospital? To avoid interference, ensure that the frequency of each system is different enough from other nearby systems.
- How much power is needed for the system?
- Where are the system transmitters positioned?
The latter two points are interrelated because by using a distributed antenna system, facility executives can better allocate space for transmitters, and decrease the power needed to supply the system. If the power can be kept at the minimum level needed, RF fields do not become overly powerful and interfere with adjacent systems.
Distributed antenna systems are also sometimes called cellular reinforcement systems; using them requires identifying suitable spaces in the facility for the antennas, but the net result is a stabilized, efficient wireless network.
Despite attempts to optimize RF fields, overlap will occur. RF site surveys will help determine range boundaries, and once those are established, facility executives will need to address the resulting inter-access point interference.
This can be tricky, particularly if the source of RF field interference resides outside the hospital. For example, one hospital in southern California has a surgical suite located above a roadway. Cell phone use by drivers on a road under the surgical suite was interfering with data-sharing technology, so the facility used a copper mesh in the subfloor of the suite to block interference.
Shielding was important for the radiology suite of another recent project. Due to the nature of the shielding, RF data had to be put onto fiber-optic cables, which were then routed into the radiology room and reconverted to RF for use within the suite.
Much like any other modern device, today’s MRIs are more powerful and more accurate than previous versions. Because of the size of modern MRIs, and because of the sizeable magnetic fields they generate, siting and shielding MRIs represents a significant design task in many hospitals.
“Modern MRIs need to be placed on slab-on-grade,” says Lake. Many second-story floors — or even ground floors over basements — simply are not adequate for the weight of MRIs.
The sheer power of three- and five-Tesla MRI machines also has to be accommodated. In MRI-equipped environments, even the scalpels need to be non-magnetic. MRI machines also receive and give off vibrations that can affect other medical devices. And there’s also the evolution of the technology to consider.
“Right now, most hospitals are at the 3-Tesla level,” says Juett. “But where will they be five or 10 years from now? That’s proving to be very difficult to design and plan for.”
Juett and Lake recommend that hospital facility executives consider future access points.
“You need to plan a navigational path for MRIs even if that means cutting a hole in a wall that gives access to the MRI suite or to a corridor that’s adjacent to the suite,” says Juett.
Alternately, some designs call for rooftop access, where a crane lowers the MRI through the roof into the suite.
Lake also urges facility executives to consider a master plan that accounts for future needs and keeps the environmental considerations of high-tech equipment in mind.
“Too often, they’ll order the equipment, allocate space to put it in, and then come to the architect or engineer,” says Lake. “And what they don’t always understand is how the various systems interfere with each other.”
The magnetic fields generated by MRIs will distort computer monitors in peripheral areas if not properly shielded, and the magnetic fields can couple to structural steel in the facility, too.
But for some facilities — older ones in particular — the cost and disruption of placing an MRI within the existing structure can be prohibitive. This need often leads facility executives to other, lower-cost options. While not a perfect solution, some hospitals are choosing to locate portable MRI scanners in a dedicated modular building on the hospital grounds.
On the Horizon
Additional medical technologies are coming, and facility executives should be aware of how these new technologies might affect their current hospital structures.
“There’s a new procedure called stereotactics, which is commonly part of a catheterization lab,” says Lake. “It’s a magnetic-based system that allows cardiac catheters to achieve a 90-degree plus bend.”
Most catheters can achieve up to a 70-degree bend, unaided. The added flexibility gives doctors access to areas impossible to reach until now. Like MRIs, stereotactic catheters use a sizeable magnetic field to achieve new levels of performance. Magnetic shields are required to help prevent disruptions of computer monitors or other medical equipment.
“Stereotactics equipment can generate a magnetic field of up to a 45-foot diameter,” says Lake. “While such a suite wouldn’t likely be that size, peripheral areas can be affected by fields that large.”
Proton therapy is another technology on the horizon. Used in oncology centers, proton therapy delivers a highly directed beam to eradicate cancerous cells. Existing standard radiation is less focused, and kills both healthy cells and cancerous ones, so proton therapy could prove a radical leap forward in cancer treatment.
In its current form, proton therapy is cost-prohibitive for most hospitals, but a handful of institutions across the nation are currently using it. They have found that the device requires special siting considerations.
Because of the high levels of radiation generated, the devices require five to seven feet of concrete shielding, according to Lake.
“These devices have severe shielding needs,” says Lake.
“We usually see the proton-therapy center constructed as a stand-alone building that’s adjacent to an existing hospital structure.”
The Surgical Suite
Because there are so many different technologies converging within healthcare facilities, facility executives need to work with administration and the in-house IT department to help ensure that the various frequencies and fields can successfully occupy the same spaces without interfering.
“In a hospital, you’ve got all kinds of transmitters vying for space,” Whaley says. Those transmitters can be on RF frequencies, or they can be transmitting vibrations, magnetic fields or radiation.
Getting all of them to work as harmoniously as possible within the structure is a daunting, but achievable, task, Juett says. “There are solutions, and in a hospital, finding the right one is critical.”
Taking Extreme Measures
Wireless networks and ever-improving MRI technology are bringing dramatic changes to surgical suites.
— Loren Synder
Questions to consider
Loren Snyder is a freelance writer and former managing editor for Building Operating Management.