Biomedical Engineering Reference
In-Depth Information
examples in which the field of electronics has been used to significantly advance medical
technology.
Many other advancements that were made in medical technology originated from
research in basic and applied physics. In 1895, the x-ray machine, one of the most important
technological inventions in the medical field, was created when W. K. Roentgen found that
x-rays could be used to give pictures of the internal structures of the body. Thus, the x-ray
machine was the first imaging device to be created. (Radiation imaging is discussed in
detail in Chapter 15.)
Another important addition to medical technology was provided by the invention of
the computer, which allowed much faster and more complicated analyses and functions
to be performed. One of the first computer-based instruments in the field of medicine,
the sequential multiple analyzer plus computer, was used to store a vast amount of data
pertaining to clinical laboratory information. The invention of the computer made it possi-
ble for laboratory tests to be performed and analyzed faster and more accurately.
The first large-scale computer-based medical instrument was created in 1972 when the
computerized axial tomography (CAT) machine was invented. The CAT machine created
an image that showed all of the internal structures that lie in a single plane of the body. This
new type of image made it possible to have more accurate and easier diagnosis of tumors,
hemorrhages, and other internal damage from information that was obtained noninvasively
(for details, see Chapter 15).
Telemedicine, which uses computer technology to transmit information from one
medical site to another, is being explored to permit access to health care for patients in
remote locations. Telemedicine can be used to let a specialist in a major hospital receive
information on a patient in a rural area and send back a plan of treatment specific to that
patient.
Today, a wide variety of medical devices and instrumentation systems are available.
Some are used to monitor patient conditions or acquire information for diagnostic
purposes—for example, ECG and EEG machines—while others are used to control phys-
iological functions—for example, pacemakers and ventilators. Some devices, like pace-
makers, are implantable, while many others are used noninvasively. This chapter
focuses on those features that are common to devices that are used to acquire and process
physiological data.
9.2 BASIC BIOINSTRUMENTATION SYSTEM
The quantity, property, or condition that is measured by an instrumentation system is
called the measurand (Figure 9.2). This can be a bioelectric signal, such as those generated
by muscles or the brain, or a chemical or mechanical signal that is converted to an electrical
signal. As explained in Chapter 10, sensors are used to convert physical measurands into
electric outputs. The outputs from these biosensors are analog signals—that is, continuous
signals—that are sent to the analog processing and digital conversion block. There, the
signals are amplified, filtered, conditioned, and converted to digital form. Methods for
modifying analog signals, such as amplifying and filtering an ECG signal, are discussed
