Medical Device Link.

Medical Electronics Manufacturing Fall 1999

EMBEDDED SYSTEMS

The Evolution of Single-Board Computers in Embedded Medical Device Development

Fred B. Salloum

There is a technological revolution in the way medical devices are conceived and developed that mirrors recent technological trends in the consumer market. As consumers, we expect—and even demand—increasing levels of information to be available in more locations with easier-to-access formats and more-user-friendly operations. In the information-critical healthcare world, designing the access to the vital data carried within medical devices is a challenge for device developers.

Two interrelated healthcare trends are fueling that same need for the creation of more-intuitive medical devices in more-accessible and more-portable formats: the explosion of home healthcare and earlier patient discharges for at-home rehabilitation from complex medical procedures.

The design process is more usage-driven than ever before. The trend toward cheaper and easier-to-use digital devices is driving a fundamental change in how products are conceived. Instead of first developing cool boxes and hoping to find uses for them, companies are identifying services and then building devices that can deliver them. To meet the need for developing cost-effective devices quickly, many device manufacturers are turning to engineering companies that specialize in shelf-ready embedded flat panels that can be almost immediately integrated into a new product. This enables manufacturers to develop a product in a three-month cycle, compared with what had been at least a one-year project.

A Driving Technology

Fifteen years ago, the proliferation of PCs triggered changes in device development. But the big computers of yesterday required more power than is needed to operate current portable devices. Because of advanced compact and low-power design capabilities, processing systems allow devices to be smaller, less expensive, and easier to use. A new generation of embedded systems includes sophisticated and inexpensive liquid-crystal displays (LCDs) and touch screens, as well as global positioning system (GPS) receivers.

Healthcare professionals at outpatient centers can now pull from their pockets Palm Pilot–type units that can automatically scan information from a device hooked into a patient. A specialist presses a few buttons, reads the LCD to see a patient's vital signs, and transmits the information to hospital's computers, where the information can be added to the patient's record. With the growing elderly population, one of the immediate uses for embedded systems and LCDs is medication management. Handheld devices help monitor that the right patient is taking the correct dosage, and the data can be communicated immediately to a pharmacy or nurse docking station. The technology minimizes the physician's difficulty in managing complex medication routines, especially for elderly patients.

Embedded-systems technology certainly enables companies to better allocate resources. A few years ago, an admission to the hospital for acoustic treatment required an audiologist along with equipment that would cost $30,000. Such admissions are now managed using handheld devices that cost less than $3000 and collect more data than PC-based systems. Hospital rooms dedicated to simple diagnostic procedures have been replaced by multipurpose outpatient surgicenters. Measurement devices have historically used desktop PCs, driven by powerful 486- or Pentium-chip technology. Most embedded applications have specific processing requirements. Using more-powerful general-purpose chips in handheld devices would be like driving a nail with a sledgehammer. Market conditions are making PCs inefficient and unproductive.

Often only a palm-sized computer is needed. These smaller devices still require the same, or greater, capabilities as their PC predecessors. This price-performance disparity between what is offered and what is required has led to the next generation in processing devices: the single-board computer (SBC) for embedded systems.

Embedded Computers Redefined

Just what is an embedded SBC? It is easy to assume it is a motherboard, which typically carries several daughter boards for specific applications. Ethernet capability, for example, has typically required its own daughter card. SBC platforms, however, are single boards that do not require additional cards and connectors (Figure 1).

Figure 1. Components of a typical single-board computer.

The size of the SBC can be as small as 4 x 6 in. and is typically less than 1 in. high. This form factor, with more-specialized, less-expensive microprocessors, results in smaller, less-expensive systems that can be designed as home healthcare devices. An SBC microprocessor is powerful, yet it is specifically suited for embedded applications. An example of this technology is the low-powered StrongARM microprocessor (Intel Corp.), a RISC (reduced instruction set computing) processor with sub-500 mW power consumption and reduced instruction requirements. Low-power processors generate virtually no heat output, and, therefore, they can be designed in tight enclosures without designing in cooling fans.

With no additional boards, these modules provide full connectivity support. Simple cable connections are no longer used for communication. Communication tools can include Ethernet, controller area network (CAN), IrDA (Infrared Data Association), and PCMCIA (Personal Computer Memory Card International Association) all on board. The value of these tools cannot be overestimated in a rapidly changing marketplace. Table I provides a guide to selecting SBCs.

The availability of technology to enable devices to transmit vital healthcare data will unquestionably change the face of the medical device industry. Ethernet capability, for example, can enable direct reporting of information to a Web address, where the information can be available to a healthcare professional. IrDA provides automatic data transmission from wireless handheld devices to centrally located servers. GPS receivers and radios, for example, can be connected using serial ports to make devices suitable for real-time notification of life-threatening situations.

Through GPS, a single system can be tracked virtually anywhere, which can be crucial for locating emergency situations. A radio provides constant communications, not only to individuals but also to monitors. This combination provides immediate details of the patient's status and location directly to a healthcare professional.

SBCs provide a powerful environment with a wide range of operating systems available to fit specific requirements and preferences. Microsoft now has Windows CE, designed specifically for the embedded world in small-footprint applications. Real-time operating systems (RTOS) are offered by such companies as Microware, Accelerated Technologies, and Wind River Systems. Although a tool kit and license cost are associated with these systems, such off-the-shelf operating systems free developers to focus on the medical application, rather than the writing and the subsequent support of a product-specific operating system. This strategy can save a company precious resources and significantly contributes to improved time-to-market.

An RTOS, which is more robust than non-real-time systems, is mission-critical to the operation of many medical devices. For example, an RTOS will service an interrupt in real time with no noticeable effect on the operation itself. These operating systems, which are often already FDA approved, provide developers with a user-friendly development environment and a strong support network.

A final attribute of consumer off-the-shelf (COTS) hardware platforms is that they greatly reduce time-to-market. A primary consideration in whether to develop a platform or buy COTS is to examine the difference of not only the time to develop the hardware, but also the additional 6—8 months it may take to get FDA approval. With technology changing so rapidly, eliminating this time lag can keep a product one step ahead of the competition.

Helping the Software Developer

This hardware evolution allows device engineers to focus on the programming or the application, and less on the vehicle needed to deliver it. In this framework, streamlined SBCs can be considered the buckets that carry high-level programming ideas and advances.

It is certain that the design of medical devices will incorporate aspects of everyday consumer applications such as the intuitive kiosks that are designed to encourage interactivity to supply key data with a touch screen interface to a flat panel. A similar intuitive design will be found increasingly in handheld devices for monitoring patient data such as blood pressure or medication levels. Intuitive design and programming will be key for devices that are dependent on patient interaction to maintain the quality of data.

With SBCs comes the ability to move existing applications, commonly stored in larger Windows NT boxes, to smaller devices and platforms. Windows CE has become the most widely used embedded operating system, and the transition from NT to CE is becoming easier. Even moving to less-popular operating systems often only requires recompiling existing programs written in C.

Additionally, SBCs are smaller and weigh less, which is critical to the importance of the SBC evolution. The smaller board size is what allows systems to move from the desktop to the palm. Smaller, complete, and fully functioning SBCs also use less power, as low as 2 W. With low power comes minimal heat output. SBCs require no cooling fans and can be integrated into a tightly enclosed device.

With on-board communication devices such as serial ports, Ethernet, PCMCIA, and CAN, portable devices can now be networked to enterprise-wide applications, providing critical information to even remote locations. The programming itself has become more user-friendly as well. SBCs readily support C++, Vision, and Rapid Development tools, enabling them to support a robust development environment.

The critical factor in embracing embedded SBCs is the reduced costs of both development and unit production. With respect to unit output, the base price of PC-based computers (PC/104s, for example) may be similar to SBCs, but cost of required daughter boards must be factored in. A cost-benefit analysis comparing the cost of an off-the-shelf SBC to allocating two to three development years to the design of a hardware product yields similar results.

Benefits to Medicine

The obvious benefit to medicine is quicker notification of more-accurate patient data in medically urgent situations. Timely transfer and storage of vital signs is also important for managing the paperwork deluge in the current outpatient environment. The intuitive format of flat panel displays and embedded systems facilitates better management of medical data. Portable devices that use less power meet the demands of the growing home healthcare market.

Embedded systems can be designed into devices to handle increasingly complex applications such as managing patients who are discharged earlier from the hospital for recuperation and rehabilitation at home. And with speedier time-to-market comes a product that is revolutionizing the industry. The merchant technology now pervasive in the software industry is improving the medical device-to-market life cycle, as the increasing availability of shelf-ready embedded systems for medical markets decreases the device development cycle.

Conclusion

Taking all aspects into consideration, the technological revolution in the medical industry reflects the evolution of diagnostic computers: from desktop units to PC/104 multistack components to single-board computers that incorporate all of the hardware requirements. SBCs also minimize power consumption and, in turn, heat output.

For many years, device manufacturers have battled with PCs to develop practical and cost-effective applications. Embedded systems are seamless and intuitive. Bar code communication can be incorporated into devices to provide more-cohesive patient management. Patient data can be transferred between multiple facilities and multiple physicians. Within five years, all electromechanical components in medical devices will likely be embedded systems.

Fred B. Salloum is director of marketing for Applied Data Systems Inc. (Columbia, MD).

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