Biomedical Engineering Reference
In-Depth Information
of photo-sensitive polymer systems is that using irradiation as a stimulus is
a relatively straightforward, non-invasive mechanism to induce responsive
behavior. However, light of UV and visible wavelengths is readily absorbed
by the skin, so UV/visible-light-responsive systems have potential limita-
tions for some biomedical applications. However, IR radiation can penetrate
skin with less risk of damage and might be more applicable for photoactiva-
tion of drug carriers within a living system [41].
2.4
Types of Medical Devices
A medical device is an instrument, apparatus, implant, in vitro reagent, or
similar or related article that is used to diagnose, prevent, or treat disease or
other conditions, and it does not achieve its purposes through chemical action
on the body. Whereas medicinal products (also called pharmaceuticals)
achieve their principal action by pharmacological, metabolic or immunologi-
cal means, medical devices act by other means like physical, mechanical, or
thermal means. Medical devices vary greatly in complexity and application.
2.4.1 Stents
A stent is a mesh 'tube' inserted into a natural passage/conduit in the body
to prevent or counteract a disease-induced, localized l ow constriction.
h e term may also refer to a tube used to temporarily hold such a natural
conduit open to allow access for surgery. Several small clinical studies have
examined the use of drug-eluting stents for the treatment of femoropop-
liteal stenosis with evidence of favorable results. Zilver PTX is a self-
expanding, nitinol drug-eluting stent with polymer-free paclitaxel coating
on its outer surface [42]. h e most common use for stents is in coronary
arteries, into which a bare-metal stent, a drug-eluting stent, or occasionally
a covered stent is inserted. Coronary stents are placed during a percuta-
neous coronary intervention procedure, also known as an angioplasty. In
order to prevent the restenosis at er stent implantation, the drug-eluting
stents, which incorporate drugs that can ef ectively reduce the prolifera-
tion and migration of smooth muscle, have been developed and several
clinically proven products are currently available on market [43].
2.4.2 Cannulas
A cannula is a tube that can be inserted into the body, ot en for the delivery
or removal of l uid or for the gathering of data. In simple terms, a cannula
