FY 2000 Wireless Technologies
- Development of a Standardized Test Method for Evaluating Interference from Electronic Article Surveillance Systems
- Measurement of Electromagnetic Energy Delivered to Models of Humans by Medical Devices
- Laboratory Testing of Cardiac and Electrical Stimulation Devices
- Wireless Medical Telemetry
The simultaneous emergence of the wireless technology revolution and a flood of devices incorporating sensitive microelectronics are leading to a highly unstable situation in which medical devices with electronics can be highly sensitive to electromagnetic interference. In FY 2000, OST investigated the potential interaction between electromagnetic security systems (e.g., electronic article surveillance systems) and implanted medical devices, such as pacemakers and neurostimulators. Further, OST helped lead a successful collaboration with the Federal Communications commission (FCC) and the American Hospital Association to establish the first Wireless Medical Telemetry Service with protections for the vital patient signals. In addition, OST responded to concerns about the radiation from cellular telephones to develop a model that predicts human absorption of radiation emitted by these products. During this year, this program contributed to (1) the development of a guidance document for medical device manufacturers and users to assess the risks of electromagnetic interference (EMI) with wireless medical telemetry, (2) labeling recommendations for electronic anti-theft security systems, and (3) the review of warnings in the labeling for implanted cardiac and nerve stimulation devices. Additionally, the program contributed to the regulatory review of many device submissions, including implanted and external cardiac stimulation devices, ultrasonic bone densitometers, Benign Prostatic Hyperplasia hyperthermia devices, and powered wheelchairs and scooters. OST provided substantial input for the development of national consensus standards for hearing aid electromagnetic compatibility (EMC) with cellular telephones, EMC of implanted cardiac stimulation devices, and the revision of a recommended practice for ad hoc EMI testing of medical device devices with portable radio transmitters, as well as for an international consensus standard for powered wheelchair EMC. Relating to human absorption of emitted radiation, OST programs contributed to the development of standard phantoms and test methodologies. Furthermore, construction of a quality assurance facility at the University of Maryland and the OST in-house measurement facility proceeded on schedule.
Development of a Standardized Test Method for Evaluating Interference from Electronic Article Surveillance Systems
Key words: electromagnetic compatibility, metal detectors, electronic surveillance systems, cardiac pacemaker, EMC
This project involves evaluating implantable medical devices for their susceptibility to electromagnetic interference (EMI) from electronic article surveillance systems (EASS) and other security systems. EASS are used in many retail stores to prevent shoplifting by detecting special tags placed on merchandise. The goal of this project is to develop a standardized laboratory test method to check the susceptibility of implanted medical devices with the magnetic fields emitted by these security systems. Because of the great similarity of EASS with magnetic-field-emitting metal detectors, this project was expanded to include evaluating EMI from metal detectors. Emissions were measured from nine different hand-held metal detectors and one walk-through metal detector this fiscal year. This project is closely associated with the OST project "Laboratory Testing of Cardiac and Electrical Stimulation Devices." This project supports the work specified in the FDA interagency agreement with the Federal Aviation Administration for evaluating medical device EMI from emissions of airport security systems (metal detectors).
Measurement of Electromagnetic Energy Delivered to Models of Humans by Medical Devices
Key words: cellular telephone, specific absorption rate, brain, quality assurance
This project is focused on the support of a critical emerging voluntary standard for testing the radiation safety of cellular phones and other wireless handsets. This technical standard defines detailed test methods for wireless phones and is being developed by the Institute of Electrical and Electronic Engineers (IEEE) with the strong participation and leadership of OST/CDRH. The standard, "Recommended Practice for Determining the Spatial-Peak Specific Absorption Rate (SAR) in the Human Body Due to Wireless Communications Devices: Experimental Techniques," sets forth the first consistent test methodology for measuring the Specific Absorption Rate (SAR) produced in a tissue-simulating human head model by cellular telephones. The lack of a standardized SAR test methodology has lead to widely varying results when the same telephone is measured at different laboratories. This variability has necessitated recalls of phones by the Federal Communications Commission, who regulates these devices in the U.S. In support of the development of the IEEE test method, CDRH began developing a measurement laboratory for determining SAR precisely. Working in collaboration with the University of Maryland (UMD), OST is also developing an SAR measurement quality assurance (QA) facility. CDRH and UMD will build and circulate an SAR evaluation system to laboratories that make cellular telephone SAR measurements. These labs will include government agencies and cellular phone manufacturers throughout the world. This QA program will ensure that by using a stable, simulated cellular phone, each laboratory can determine the SAR induced in a tissue-simulating human head model with a high degree of accuracy and precision.
Laboratory Testing of Cardiac and Electrical Stimulation Devices
Key words: electromagnetic interference (EMI), electromagnetic compatibility (EMC), electrical stimulation devices, nerve stimulation devices, cardiac stimulation devices, cellular telephone, metal detectors
This project is intended to assess the electromagnetic compatibility (EMC) of several high-priority ambulatory and implanted electrical stimulation medical devices. During this fiscal year, OST participated actively in finalizing a voluntary standard that defines a detailed laboratory test method for the in vitro evaluation of electromagnetic interference (EMI) of implanted cardiac pacemakers and defibrillators from cellular telephones. The standard was developed under the sponsorship of the Association for the Advancement of Medical Instrumentation (AAMI) Pacemaker Task Group. The standard test method is based on a method developed by OST and modified with input from various other labs, including those of medical device manufacturers. OST, the Office of Device Evaluation (ODE) in CDRH, and many other groups completed a final draft of this detailed, standardized test method in FY 2000. In another effort dealing with the EMC of Electrical Stimulation Devices, OST collaborated with personnel from ODE and the Office of Surveillance and Biometrics in a CDRH ad hoc group. This group identified over 20 reports of EMI of implanted neural stimulators that caused patient injuries. These reports included EMI from a variety of magnetic-field emitting security systems.
This work was done partially in support of an Interagency Agreement (IAG) with the Federal Aviation Administration. The IAG deals with evaluating medical device EMI from emissions of airport security systems (metal detectors).
Wireless Medical Telemetry
Key words: wireless medical telemetry, EMI, FCC, AHA
Wireless medical telemetry (WMTS) systems are used to monitor patients at a distance in the intermediate care units of hospitals and in many other health care facilities. In recent years, failures of telemetry systems that were monitoring patients occurred because of electromagnetic interference (EMI) from the new digital television transmitters and other wireless broadcast services that shared the same frequencies as the WMTS. During FY 2000, FDA worked in partnership with the Federal Communications Commission (FCC), the American Hospital Association (AHA), telemetry manufacturers, and clinicians to help the FCC create new, dedicated frequency bands for Wireless Medical Telemetry Services (WMTS). The CDRH EMC group, led by OST, developed recommendations to address the issue of EMI and the changes to the radio services where wireless telemetry has traditionally operated. Letters were sent to telemetry manufacturers, users, and clinicians, encouraging manufacturers and users of telemetry devices to migrate to the new WMTS bands. WMTS provides protections against EMI and reduces the risk of interference to the medical telemetry from others in band radio sources. To assist manufacturers in bringing products using the WMTS to market in a least burdensome manner, a guidance document titled "Deciding when to Submit a New 510(k) for a Change to an Existing Wireless Medical Telemetry Device" was developed. Information about the wireless medical telemetry EMI issue, and links to the guidance, wee published on the FDA/CDRH web page.