Introduction - Computational Intelligence in Biomedical Engineering - page 3

aging medical information systems (ARAMIS) system developed at Stanford
University in 1972 was also based on the PROMIS structure but was designed
to collect time oriented data to record a patient's recovery progress. Continued
developments in technology since then have now allowed medical records to be
made accessible online and to be carried around in personal digital assistants
(PDAs) or smart cards.
1.1.2 Medical Instrumentation
There are several categories of medical instruments ranging from those used
in surgery to the ECG for monitoring the cardiovascular system. In this topic,
we will be mostly concerned with medical instruments that record physio-
logical signals including the ECG, EMG, and EEG that measure the voltage
potentials on the skin. These measurements are done by placing electrodes
on specific locations of the body. Nonevasive electrodes are surface electrodes,
which can be placed on the skin whereas needle electrodes are evasive in the
sense that they must pierce the area to obtain measurements. Besides elec-
trodes, other sensors are also available to transduce quantities such as body
temperature and blood pressure.
Detected electrical signals can be processed using a computer or simply a
digital signal processor (DSP) board. The processor receives the measurement
signals and then performs specific tasks such as administering intravenous
drips or alerting the doctor. Other instruments such as the heart pacemaker
are surgically implanted. Modern pacemakers have wireless communication
capabilities, which enable them to display operating parameters or vital signs
on nearby monitors. The device parameters such as amplitude of heart stim-
ulation may also be adjusted in a similar fashion.
A major source of noise in medical instruments is due to the polarizable elec-
trodes. When these electrodes are in direct contact with the skin, a two-layer
charge develops between the electrode and the gel surface. Movement of the
electrode against the electrolyte results in a change of the half-cell potential
and causes distortions to the recordings made between two moving electrodes.
This is known as a motion artifact, which is the result of a superimposed
biosignal and is a serious measurement noise source. Some researchers have
shown that the outer skin layer, stratum corneum, possesses dielectric or piezo-
electric properties that increases the probability of motion artifacts (Togawa
et al., 1997). Unfortunately, removal of this skin layer is not advisable due to
risk of infection.
1.1.3 Medical Systems
Biomedical systems are designed to collect, process, and interpret medical
data. In the early 1980s, computer programs were designed to model physical
systems of the body such as the cardiovascular system and biological pro-
cesses such as respiration. Unfortunately, more complex models such as the