Biomedical Engineering Reference
In-Depth Information
Fig. 19.1
Left
: Sketch of limitations and characteristics of an intra-vascular medication.
Right
:
Comparison of extra-vascular medications in the dispersion of therapeutics after the same time
of pharmaceuticals. Within chemotherapies, the most commonly used method is the
intravenous application of drugs leading to a more or less regular distribution by the
blood circulation. Within this method, only a part of the therapeutic agent reaches
the target area. However, in case of brain tumors, the drugs have to pass the blood-
brain barrier (BBB) to enter the tissue. Unfortunately, this is not possible for most
of the commonly used therapeutic macro-molecules in brain-tumor therapies, cf.
Fig.
19.1
(left).
A possible solution of the delivery problem is a direct insertion of therapeutic
agents into the extra-vascular space in order to bypass the BBB. Herein, two differ-
ent basic approaches can be distinguished:
•
Implantation of release systems:
- providing a constant concentration at the point of implantation
- driving the distribution by diffusion as a result of concentration gradients
•
Infusion of interstitial fluid with dissolved therapeutic agents:
- distributing therapeutic agents by both concentration and pressure gradients
- resulting in an extensive spreading of the therapeutic particles, see Fig.
19.1
(right)
The latter more promising approach represents the focus of this contribution and is
generally known as convection-enhanced drug delivery (CED) of therapeutics. This
pioneering method was introduced by Bobo et al. (
1994
) and clinically established
by researchers from the National Institutes of Health (NIH). Through a small hole
in the skull, a catheter is directly placed in the brain tissue, while the therapeutic
solution is infused by an external medical pump. With this method, large target areas
can be supplied. However, the prediction of the distribution profile is challenging
since the distribution is affected by the complex nature of living brain tissue. Based
on these remarks, the goal of this contribution is the continuum-mechanical and
computational simulation of living brain tissue with application to the description of
the CED process. We hope that a practising surgeon can be pre-operatively assisted
in his decisions by our and comparable numerical studies.
