Introduction to computing - Biomedical Engineering Desk Reference - page 26

Figure 2.1b-1 An automatic sphygmomanometer for home use. Image courtesy of Omron Healthcare.

Instrumentation such as the BP monitor, CT or MRI
imager, and the microscope have a common structure.
In all cases, the computer controls the electronic
interface (the user interface and data collection), which
is connected to the subsystems that sense the tissue
properties and control the sensor.
All of these functions could be performed by a trained
user, but then instruments such as the BP monitor could
not be put into the hands of the consumer for two rea-
sons: First, the general consumer is untrained. Second,
human performance changes over time. The computers
embedded in the instruments have helped to standardize
the operation, so that non-trained users can operate the
BP monitor and other medical devices while being in
better control of their healthcare.
Once a computer is given a standard set of in-
structions, the performance will be the same each time
the device is used, unless there is a hardware failure.
Some of the advantages of using computers are:
1. The actions directed by the computer and its
program are reproducible : the operation will
not change over time unless one or more parts
(the electronics, actuator, or sensor) fail.
2. The precision and accuracy can be controlled:
precision is the smallest possible resolvable event; it
differs from accuracy, which is how close you can get
to the truth (the real property). Precision and
accuracy are dependent on both the sensors and the
computation. The emphasis in this text will be on
how we can best optimize the computer programs to
maximize the precision and accuracy of the results.
Computers are not without their drawbacks. Some of the
disadvantages of using computers instead of human
control are:

1. Computers require precise and complete
instructions. There is no room for ambiguity or
assumptions.
2. All too often, program testing is not clear or
complete. Testing a computer program, especially
a large computer program, can be a full-time job by
itself. You often have to worry about unanticipated
input or conflicting input that is not expected. You
may collect more data than you have accounted for.
The number of possible combinations of inputs is
exponential in the number of independent variables;
for a moderate number of input variables, the
number of possible inputs is too large to test.
3. There can be logic errors, or syntactic errors, that
can later cause execution errors. In very large
applications, like bioinformatics programs, special
Web interfaces are built just to keep track of the
bugs. A good example is http://www.biojava.org , the
Web site for a set of Java-based tools for processing
biomedical data, such as gene sequences.

Besides controlling or automating equipment, computers
can make biomedical engineers more efficient by:
1. Providing design tools, including simulation (using
tools such as Simulink, Pro-E, and ANSYS)
2. Keeping documentation (using tools such as
MS Word or Excel)
3. Providing test procedures and results (using tools
such as MATLAB and LabVIEW)

The emphasis here is to help the new biomedical engi-
neer develop computer programs that control the precision
and accuracy of the measurements and computations as an
integral part of solutions to real-world bioengineering