Biomedical Engineering Reference
In-Depth Information
In this example, the support vectors are shown as dashed lines that define the edges
of each of the categories. Their orientations are defined to maximize the margin (distance
between the two vectors).
5.7
ISOLATION BARRIERS
Many biomedical applications require that that power be conveyed one way across an
isolation barrier and that signals be conveyed in the other direction. These serve two
purposes. In the first, isolation is required to ensure that, in the case of electronic failure,
high voltages cannot be introduced into the patient through electrodes attached to the
body. In the second, electronics are mounted under the skin or within the body cavity, so
a method of charging internal batteries and obtaining telemetry is required.
5.7.1 Implant Systems
Most implant systems share a common framework, as shown in Figure 5-69, which con-
sists of an external signal processing unit for biological sensory information (e.g., sound,
images), a bidirectional telemetry unit, an internal signal processing module, a stimulus
generator/driver, and an electrode array to interface to tissue or nerves (Finn and LoPresti,
2003).
It is envisaged that ultimately most prostheses will be totally internal, with sensors,
processing, and actuation electrodes all self-contained within a biocompatible module.
However, during the development phase or while the technology is immature, there are
myriad advantages of including both internal and external modules, including decreased
risk of adverse reaction to implanted materials, lower internal heat dissipation and, of
course, ease of refinement to both the hardware and software.
FIGURE 5-69
Schematic diagram
for a generic
implantable system
[Adapted from (Finn
and LoPresti 2003).]
