Biomedical Engineering Reference
In-Depth Information
before closure, and installing a drain. Re-implantation may
be attempted under the following conditions (see the
section “Endpoints” below).
(A)
(B)
It is part of research design described in the IACUC
approved protocol.
l
Additional surgery does not exceed the number of
permitted surgeries.
l
The subject animal has been declared healthy and fit by
the veterinarian.
l
It will not jeopardize the subject animal's life or
significantly compromise its well-being.
l
There are no other proven and practical alternatives.
(C)
l
It is a gainful means to forward the research.
l
Overgrown Granulation Tissue
Granulation tissue formation is part of a normal healing
process. Under certain conditions, such as infection, self-
mutilation, or a local reaction to a chronically implanted,
foreign material, this tissue grows uncontrollably and
becomes very vascular and secretive. Treating local infec-
tions, frequent cleaning of the interfaces and removal of
cellular debris, removal of foreign bodies, cauterizing or
trimming under local block, or anesthesia may facilitate
management of granulation tissue. Use of topical cortico-
steroids is of limited value. Other agents such as anti-
mitotic 5-flurouracil (5-FU) have been used to control the
growth of tough supradural connective tissue inside the
chronic cranial recording chambers. 5-FU has been shown
to minimize the dural growth and scar tissue formation by
depressing the fibroblast division, to reduce vascularization
and blood loss during removal, to reduce the number of
necessary procedures to remove the growing tissue, and
inhibit bacterial infections over a period of 15
30 weeks
(
Spinks et al., 2003
). Sometimes the therapeutic efforts fail
and force an explantation surgery, a radical but effective
resolution.
e
FIGURE 14.8
Sterotaxic devices. (A,B) Older, NHP stereotax man-
ufactured by Kopf. (C) Model 1404 Heavy-Duty Research Sterotaxic for
cats and monkeys by Kopf Instruments. (Courtesy of Kopf.)
Chronic Cranial Implants and Ancillary
Devices
Stereotaxy
A stereotactic apparatus is commonly used in cranial
surgical manipulations in humans and nonhuman primates
(
Figure 14.8
). The apparatus permits nontraumatic and very
precise positioning, immobilization, and execution of
coordinates in search of specific areas.
from stainless steel or titanium (more expensive but
reduces broad shadowing in the MRI field) (
Figure 14.9
).
Multi-electrode Arrays
These are devices that contain multiple plates or shanks
through which neural signals are obtained or delivered.
They are small squares with up to 100 microelectrodes that
may be placed directly on the cortex (subdural) and
punched in with an air puff or placed on the dura (epidural)
(
Figure 14.10
A,B). Each electrode in the array contributes
a wire to a wire bundle that leads to a connector (
Figure
14.10
C) anchored directly to the cranium with screws.
Head Restraining Post
These are restraining devices that are attached directly to
the cranium with screws or embedded in a methacrylate cap
anchored to the cranium with screws. They are usually
custom made (limited designs are available commercially)
