Microwave and RF Technology in Medical Applications

For many years, microwave component companies have provided components for medical imaging applications such as magnetic resonance imaging (MRI) systems. While imaging applications continue to provide solid opportunities, many other medical application areas are beginning to open the door to wireless microwave and RF technology. For example, remote monitoring allows patients at home to wirelessly send health information such as blood pressure and pulse to their doctors. Other innovations are also helping hospitals and medical centers track the location of assets and individuals. Between the existing imaging market and the new opportunities that wireless technology is creating, the medical industry has become a real new market that many microwave and RF companies are targeting. Fortunately, many of these opportunities only require these companies to use their existing expertise in telecommunications and wireless LANs.

The use of imaging devices such as MRI is increasing, and more than 60 million MRI diagnoses are now performed worldwide each year. They are commonly used to diagnose a variety of diseases and injuries, such as Alzheimer's disease, cancer cells, and ligament tears. Imaging systems use a variety of RF/microwave components, including oscillators, transmitters, and antennas. For example, Analog Devices now offers the AD5791, a 20-bit data converter (DAC) designed to improve imaging resolution.

The AD5791 features true parts-per-million (ppm) resolution and accuracy (Figure 1). The AD5791 has a relative accuracy specification of ±1LSB DNL, ​​ensuring consistent operation. The DAC has a low-frequency noise of only 0.025ppm and an output drift of only 0.05ppm/C. Such low noise reduces unwanted image artifacts, thereby reducing the need for multiple MRI scans, so patients can be diagnosed and treated in a shorter time. The output can be configured for standard unipolar (+5V, +10V) or bipolar (±5V, ±10 V) ranges. The AD5791's 3-wire serial interface operates at a clock rate of 50MHz.

Figure 1: ADI's single-chip DAC has high precision, enabling very clear diagnostic imaging pictures.

Spectroscopic applications are another growth market for RF/microwave technology in the medical field. It is essentially a chemical analysis performed by shining light on a specimen. Recently, Agilent and the University of Texas at Dallas announced plans to create a millimeter-wave and submillimeter-wave electronic characterization facility. The facility will initially support feasibility studies of 180 to 300 GHz spectroscopy technology on CMOS for healthcare and security applications.

A new comparator product line from Hittite Microwave is also targeting spectroscopy applications. The company says the six comparators have the following features: 20Gbps rate, 150mW power consumption, 120ps clock to data output delay (Figure 2). Typically, they have a minimum detectable input pulse width of 60ps, and the rated random jitter is only 0.2ps. These comparators support a common-mode input voltage range of ±1.75V, and their typical overdrive and slew rate deviation is less than 10ps. The HMC874LC3C, HMC875LC3C, and HMC876LC3C monolithic comparators have high-speed latching characteristics with programmable hysteresis, and they provide low-swing PECL, CML, and ECL output drivers, respectively.

The company also released three new monolithic 10GHz comparators with level latch inputs: HMC674LC3C, HMC675LC3C and HMC676LC3C. These three comparators support 10GHz input bandwidth, 85ps transmission delay and 60ps minimum pulse width under 0.2psRMS random jitter. They have 10ps overdrive and slew rate deviation and power consumption of less than 140mW. These devices have differential latch control and programmable hysteresis and can be configured to work in latch mode or as tracking comparators. Like other devices in this series, they provide low swing PECL, CML and ECL output drivers respectively.

Remote monitoring application

Remote monitoring involving wireless networks in hospitals, clinics and homes is perhaps the most thriving medical market. The most attractive aspect of remote monitoring is that it can also be used to communicate with and educate patients. Of course, the need to send and receive information at the same time will have different requirements for the required equipment and network infrastructure. A clinical study conducted in Illinois used remote monitoring to manage the administration of the drug Gleevec. Gleevec is a drug developed and produced by Novartis for the treatment of chronic myeloid leukemia. The study will evaluate the use of a mobile phone-based personalized drug management system called eMedonline.

In this study, eMedonline, as a "smart service", takes full advantage of radio frequency identification (RFID) and the wireless capabilities of mobile phones to turn smartphones into drug sensors. The mobile phone wirelessly reads and collects drug data from the RFID "smart tags" on the drug packaging in real time. While monitoring patient-reported results, it helps verify whether the patient has taken the right medicine at the right time. The data in the mobile phone is wirelessly sent to a secure server, which is then used for clinical review and analysis. Alerts can be sent according to the situation to intervene in missed medications or adverse conditions so that they do not become serious health risks. The original intention of this study comes from the fact that patients often do not follow their doctors' orders.

In a recent demonstration in Boston of a program designed to improve medication adherence, the Bluetooth-enabled Vena inhaler recorded medication dosage history in real time and wirelessly. The data was uploaded to a user-centric software platform called Vena-Hub, which alerted patients when they missed their medications. The Vena-Hub, which is used to collect data from the ecosystem of wireless medical devices, is also the portal for Vena-enabled spirometers. Data such as medication adherence and lung capacity are combined with other variables such as pollen counts to form a series of recommendations and relevant information, which are then automatically sent to users through alerts. Alerts may be sent through online readers, social networks, emails, or even text messages.

Another benefit of remote monitoring is that specialists will be able to communicate with patients in rural areas, who will not have to travel long distances. For example, AT&T recently announced an agreement with the University of California. As part of the three-year, $27 million contract, AT&T will provide managed network services to support the telehealth program. The California Telehealth Network is a statewide alliance of healthcare, technology, government and other stakeholders that sought funding from the Federal Communications Commission's (FCC) Rural Health Care Pilot Program. The network is building a statewide network infrastructure that connects small hospitals and clinics with large hospitals and specialists within them. When the network is completed, it will cover more than 860 sites across the state.

Wireless network standards are also increasingly being used for asset tracking projects. For example, Henry Mayo Hospital has contracted with AT&T to deploy AeroScout's Wi-Fi RFID asset tracking and temperature monitoring solutions. As the disaster resource center for Los Angeles County, Henry Mayo Hospital is responsible for providing medical equipment, medications, and care to the community at large during emergencies. AeroScout's asset tracking and management solutions are designed to help the hospital track the use of critical assets such as beds, wheelchairs, gurneys, patient-controlled analgesia pumps, and infusion pumps throughout the hospital. In addition, AeroScout's temperature monitoring solutions simplify the implementation of requirements related to the Joint Commission International Hospital Accreditation regulations by ensuring that refrigerator temperatures meet the temperature range required to preserve medications, tissue samples, and other temperature-sensitive materials.

At the Saint-Jerome Health and Social Services Centre in Quebec, Canada, hospital staff wear Ekahau pager tags so they can be easily located. The T301BD Wi-Fi pager tags have two-way communication capabilities, allowing users to send and receive text messages. The pagers also include a special button that can be pressed in the event of an emergency. The Ekahau Real-Time Location System uses the hospital's existing Wi-Fi network to locate the small, button-battery-powered tags within the network's coverage area within seconds.

These products and services are some of the more dominant and growing applications within the healthcare industry today. As technology advances and broadband initiatives are implemented, more opportunities will emerge. The backbone of these new services and systems relies on wireless networks to collect and deliver information. At the same time, microwave companies will continue to reap success in areas such as imaging. Many factors will result in a growing market that provides profitable opportunities for companies and their products.

Wireless Technologies in Medical Applications

To enter the medical market, it is important to understand which wireless standards are dominant. Interestingly, the dominant technologies are mainstream technologies such as ZigBee or IEEE 802.15.4, Bluetooth, IEEE 802.11x, and radio frequency identification (RFID). Looking ahead, the Continua Health Alliance seems to be driving the development of standards in the healthcare field to a large extent. Its mission is to establish a system that makes personal health solutions interoperable to promote autonomy and enable individuals and institutions to better manage health and protect well-being.

The Continua Health Alliance has approved ZigBee Health Care as a low-power local area network (LAN) standard for sensing and control in professional environments, homes, activity centers, and large campuses. ZigBee Health Care is a global open standard for interoperable wireless devices that can safely monitor and manage health services for non-critical, low-risk conditions such as chronic disease, obesity, and aging. ZigBee Health Care fully supports IEEE 11073 devices. ZigBee Health Care provides interference-free wireless connectivity and can support thousands of devices on a single network. ZigBee can coexist peacefully with other wireless technologies such as Wi-Fi, which is a key requirement for protecting patient safety and ensuring applications in medical facilities. ZigBee Health Care devices can interact with other ZigBee wireless technologies already deployed in consumer electronics, home automation, and commercial building automation.

Companies such as Freescale use ZigBee for a variety of healthcare products. The newly approved ZigBee Health Care standard provides a global open standard for low-power wireless devices with interoperability. In this way, it ensures safe monitoring and management of non-fatal, non-emergency healthcare services such as chronic disease management, elderly care, health care, hospitalization management, and asset tracking. It supports thousands of devices within a network and provides full support for IEEE 11073 devices, allowing each device to pass FDA certification.

ADI's analog circuit ADF7242, which works in the 2.4GHz industrial, scientific and medical (ISM) band, supports a rate of 250kbps in IEEE 802.15.4 mode. This transceiver can be used to implement solutions based on protocols such as ZigBeeIPv6/6LowWPAN. ADF7242 supports IEEE 802.15.4 and GFSK/FSK dual-mode working modes, that is, the same device can support standards based on the IEEE 802.15.4 protocol at a rate of 250kbps, and can support proprietary protocols using GFSK/FSK modulation schemes at a rate of 2Mbps.

More than a year ago, Continua approved Bluetooth Low Energy in the second version of its design guidelines. Bluetooth Low Energy wireless technology is a key feature of the Bluetooth Core Specification 4.0, which enables small wireless products and sensors powered by coin-cell batteries. These small, low-cost solutions are expected to foster a variety of medical meters, remote controls and medical sensor markets.

Texas Instruments (TI) is one of the pioneers of using Bluetooth for wireless medical applications. The company has integrated its seventh-generation Bluetooth product CC2560 with an embedded Bluetooth stack to run on its MSP430 microcontroller (MCU). Designers can use the low-power MSP430 MCU to connect to analog signals, sensors and digital devices simultaneously in a range of portable devices.

Of course, as new medical services emerge, more standards and technologies will emerge, such as combining fourth-generation communication standards such as Long Term Evolution (LTE) and broadband technologies such as WiMAX to implement medical applications.