Biomedical Engineering Reference
In-Depth Information
DESIGN OF SAFE MEDICAL
DEVICE PROTOTYPES
Military downsizing, government cutbacks, and corporate reengineering had the opposite
e
ect on the medical industry as they did on all other areas of technology. As R&D budg-
ets shrank, early-generation technologies that had long been considered obsolete for space,
security, and military applications suddenly found a thriving environment in the develop-
ment of new medical devices. For example, cruise-missile tracking technology has been
adapted to steer powerful x-ray beams to destroy brain and spinal-cord tumors precisely
without the need of surgery; software used for interpreting spy-satellite images has been
used as the basis for detecting subtle but highly virulent breast cancers that were often
overseen in visual interpretations of mamographic images; and miniaturized high-energy
capacitors developed for portable laser weapons may make it possible to build smaller and
lighter automatic implantable cardiac de
ff
brillators.
Many other examples of these dual-use technologies continue to appear with no end in
sight, making medical electronics one of today's fastest-growing and most promising tech-
nology-based industries. Fortunately for the entrepreneurs among us, prototypes of many
new medical instruments can still be developed in a garage-turned-laboratory without the
need for esoteric technologies recycled from multibillion-dollar satellite and weapons pro-
grams. Rather, a fresh idea, a personal computer, and some simple interface circuitry is all
it may take to start the next revolution in medical care.
Despite how simple or complex a medical electronic instrument prototype may be,
however, safety must be the primary objective throughout the development e
fi
ort. Becom-
ing intimately familiar with electrical safety standards is probably the most important thing
that a newcomer to the
ff
field can do, because the dangers involved in interfacing with the
human body are often counterintuitive to an otherwise knowledgeable engineer. For exam-
ple, did you know that a 60-Hz current of barely 10
fi
A
fl
flowing through the heart has the
potential of causing permanent damage and even death?
The objective of this chapter is to introduce the basics of designing and constructing
electrically safe medical instrument prototypes. We
first present an overview of electrical
safety compliance requirements, proceed to look at a number of circuits that enable safe
interfacing with medical electronics, then review safety testing methods, and
fi
fi
finally, show
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