For years, microwave companies have been selling components for medical imaging applications, such as magnetic resonance imaging (MRI) systems. While imaging continues to offer viable opportunities, many additional medical application areas are emerging for wireless microwave and RF technologies. Remote monitoring, for example, allows patients to stay at home while health status reports, such as blood pressure and pulse rate, are sent wirelessly to their physicians. Other innovations are helping hospitals and medical centers keep track of both assets and individuals. Between the existing imaging markets and the new opportunities being created by wireless technology, the medical industry has become a viable new market on which many microwave and RF companies have set their sights. Luckily, many of these opportunities simply require that these firms leverage their existing expertise in telecommunications and wireless localarea networking.

For imaging equipment like MRIs, the frequency of procedures is rising. Currently, more than 60 million diagnostic MRI procedures are performed worldwide each year. They are commonly used to diagnose a wide range of illnesses and injuries, such as Alzheimer's disease, cancerous tumors, and torn ligaments. Imaging systems incorporate a variety of RF/microwave devices including oscillators, transmitters, and antennas. Analog Devices, Inc., for example, now offers a data-conversion integrated circuit (IC) designed to improve imaging resolution.

The AD5791 20-b digital-to-analog converter (DAC) features true 1-part per million (ppm) resolution and accuracy (Fig. 1). The 20-b AD5791 offers a relative accuracy specification to 1 LSB DNL, which ensures monotonic operation. The DAC exhibits 0.025-ppm low-frequency noise and 0.05-ppm/C output drift. With such low-noise performance, it lessens unwanted image artifacts and thereby reduces the need for multiple MRI scans. As a result, patients can be treated within a shorter time period. The output can be configured for standard unipolar (+5 V, +10 V) or bipolar (5 V, 10 V) ranges. The AD5791's three-wire serial interface operates at clock rates to 50 MHz.

Another medical growth area for RF/ microwave technology is spectroscopy, which is essentially chemical analysis achieved by shining light on a sample. Recently, Agilent Technologies, Inc. and the University of Texas at Dallas announced plans to create a millimeter- and sub-millimeterwave electronics characterization facility at the Texas Analog Center of Excellence (TxACE). The facility will initially support research to study the feasibility for 180-to-300-GHz spectrometry in complementary metal oxide semiconductor (CMOS) technology for healthcare and security applications.

Spectrometry also is among the target applications of a new comparator product line from Hittite Microwave Corp. According to the firm, the six comparators deliver speed to 20 Gb/s while consuming 150 mW and providing 120 ps clock-to-data-output delay (Fig. 2). Typically, they provide a minimum input detectable pulse width of 60 ps while random jitter is specified at only 0.2 ps rms. The comparators rely on a common-mode input-voltage range of 1.75 V. They exhibit typical overdrive and slew rate dispersion below 10 ps. The HMC874LC3C, HMC875LC3C, and HMC876LC3C monolithic comparators feature high-speed latches with programmable hysteresis. They offer reducedswing PECL, CML, and ECL output drivers, respectively.

The firm also released three new monolithic, 10-GHz comparators that feature level-latched inputs. The HMC674LC3C, HMC675LC3C, and the HMC676LC3C comparators support 10-GHz input bandwidth while providing 85 ps propagation delay and 60 ps minimum pulse width with 0.2 ps RMS random jitter. They boast overdrive and slew rate dispersion of 10 ps and power consumption of less than 140 mW. These devices feature differential latch control and programmable hysteresis. They may be configured to operate in either latch mode or as tracking comparators. Like their siblings, they provide reduced-swing PECL, CML, and ECL output drivers, respectively.

REMOTE MONITORING
In hospitals, clinics, and homes, probably the most burgeoning medical market is in remote monitoring, which involves wireless networks (see "Healthcare Standards Reveal The Usual Suspects"). One intriguing aspect of remote monitoring is that it also can be used to communicate with patients and educate them. Of course, the need to both transmit and receive information will place different requirements on the equipment and network infrastructure needed. In one clinical study taking place at the Rex Cancer Center of Wakefield, IL, telemonitoring is being used to manage the administration of Gleevec, a drug developed and manufactured by Novartis to treat chronic myeloid leukemia. The study will assess the use of a cell-phone-based, personalized drug-management system called eMedonline.

In this study, eMedonline is implemented as a "smart service" that leverages the wireless capabilities of radiofrequency identification (RFID) and cell phones by turning a smartphone into a medication sensor. Medication data read from a RFID "smart label" on the medication package is collected wirelessly by the phone in real time. It helps to verify that patients are taking the right drug at the right time while monitoring patient reported outcomes. Data from the phone is sent wirelessly to a secure server, where it is available for clinical review and analysis. Alerts can be triggered, enabling intervention in the case of missed medications or adverse events before they become a significant health risk. This study was inspired by the fact that patients do not often comply with the directions they are given.

At the Front End of Innovation (FEI) in Boston, MA earlier this month, Cambridge Consultants (www.cambridge consultants.com) also displayed a solution to improve drug compliance. The Bluetooth-enabled Vena inhaler records dosage history instantaneously and wirelessly. The data uploads to a consumerfocused software platform called Vena- Hub and alerts the user when they have missed any scheduled doses. Designed to capture data from a user's ecosystem of wireless medical devices, VenaHub is a portal for the Vena-enabled spirometer as well. Data on compliance and lung capacitycombined with other variables like pollen count-inform a set of recommendations and relevant information that is automatically sent to the user via an alert. This can come in the form of an online reader, social network, e-mail, or even a text message.

Another benefit of remote monitoring is that specialists will be able to communicate with patients in rural areas without those patients having to necessarily travel a great distance. For example, AT&T recently announced an agreement with the University of California. As part of a three-year, $27-million contract, AT&T will provide managed network services in support of the telehealth initiative. The California Telehealth Network (CTN) is the result of a statewide coalition of healthcare, technology, government, and other stakeholders that sought funding from the Federal Communications Commission's (FCC's) Rural Health Care Pilot Program. The network is building a statewide network infrastructure that will connect smaller hospitals and clinics to larger hospitals and their specialists and experts. When complete, the network will include more than 860 sites throughout the state.

Wireless-networking standards also are being increasingly implemented for asset-tracking programs. For example, Henry Mayo Newhall Memorial Hospital has contracted with AT&T for the deployment of AeroScout's (www.aeroscout. com) Wi-Fi RFID Asset Tracking and Temperature Monitoring solutions. As a disaster resource center for Los Angeles County, Henry Mayo is responsible for providing medical equipment, medication, and care to the entire community in the event of an emergency. The AeroScout asset-tracking and management solution is designed to help the hospital track the use of key assets, such as beds, wheelchairs, gurneys, patient-controlled analgesia pumps, and infusion pumps, throughout all departments. In addition, AeroScout's Temperature Monitoring solution is used to facilitate compliance with Joint Commission regulations by ensuring that refrigerator temperatures remain within the specified range for pharmaceuticals, tissue samples, and other temperature-sensitive material.

At the St-Jrme Health and Social Services Center in Quebec, Canada, hospital staff wear the Ekahau pager tags so that their location can be easily pinpointed. The T301BD Wi-Fi pager tags are capable of supporting two-way communications, enabling users to send and receive text messages. The units also include a dedicated button that can be triggered in the event of an emergency. Ekahau RTLS leverages a hospital's existing Wi-Fi network to locate small, battery-powered tags anywhere within the footprint of the network in a matter of seconds.

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These products and services are some of the more prominent, growing applications in today's healthcare industry. As technologies evolve and the US broadband plan is rolled out, more opportunities will emerge. The bulk of these new services and systems rely on wireless networking to gather and provide information. At the same time, microwave firms will continue to enjoy success in areas like imaging. The combined result is a growing market that offers profitable opportunities for a variety of firms and their wares.

Healthcare Standards Reveal The Usual Suspects
To enter the healthcare market, it is important to know which wireless standards are most prominently implemented. Interestingly, the mainstay technologies are mainstream wireless standards like ZigBee or IEEE 802.15.4, Bluetooth, IEEE 802.11x, and technologies like radiofrequency identification (RFID). Going forward, it seems like the Continua Health Alliance will largely drive standards development for the healthcare segment. Its mission is to establish a system of interoperable personal telehealth solutions that fosters independence and empowers people and organizations to better manage health and wellness.

ZigBee Health Care, for example, has been endorsed by the Continua Health Alliance as a low-power local-area-network (LAN) standard. ZigBee is being used by companies like Freescale in a number of its healthcare-targeted products. The newly ratified ZigBee Health Care standard provides a global, open standard for interoperable, low-power wireless devices. In doing so, it enables secure monitoring and management of noncritical, low-acuity healthcare services targeting chronic disease management, elderly care, wellness, in-patient, and asset tracking. It supports thousands of devices on a single network and provides full support for IEEE 11073 devices, making each device eligible for FDA certification.

An RF circuit from Analog Devices, which works in the 2.4-GHz Industrial, Scientific, and Medical (ISM) band, supports 250 kb/s in IEEE 802.15.4 mode. The transceiver may be used to implement solutions based upon protocols like ZigBee IPv6/6LowWPAN. The ADF7242 features dual-mode IEEE 802.15.4 and GFSK/FSK operations, whereby the same device is capable of supporting the IEEE 802.15.4-based protocol standards at 250 kb/s as well as proprietary protocols to 2 Mb/s using GFSK/FSK modulation schemes on a single chip.

More than a year ago, Bluetooth low energy was approved for the Continua Version Two Design Guidelines. The Bluetooth low-energy wireless technology is the hallmark feature of the Bluetooth Core Specification Version 4.0. It makes possible small, coin-cell-battery-powered wireless products and sensors. These compact and low-cost solutions are expected to spawn a market for watches, remote controls, and healthcare sensors.

Texas Instruments is one proponent of Bluetooth for wireless medical applications. Recently, the firm coupled its seventh-generation Bluetooth offering, the CC2560, with an embedded Bluetooth stack running on its MSP430 microcontroller (MCU). Designers can use the low-power MSP430 MCU to simultaneously interface to analog signals, sensors, and digital components in a range of portable devices.

Clearly, more standards and technologies will come into play as new healthcare services emerge. The Continua Health Alliance recently praised the FCC for the healthcare provisions in the National Broadband Plan. The plan identifies and makes broad recommendations in four critical areas: reimbursement, modernizing regulations, increasing data capture and utilization, and providing sufficient connectivity to better enable the provision of healthcare. According to the alliance, the plan's implementation would advance connected health and encourage the adoption of remote patient monitoring. Most likely, it will do so via a combination of telecommunications standards like fourth-generation Long Term Evolution (LTE) and broadband technologies like WiMAX.