Biomedical Engineering Reference
In-Depth Information
the human body to perform, augment or replace natural bodily functions.
Though there are many types of imaging used in the biomedical sciences, in
this chapter imaging refers to observations and measurements carried out
with microscopes using light, electrons or scanned molecular mechanical
probes.
The following defi nitions for images, imaging and microscopy are presented
in order to clarify imaging concepts that appear later in this chapter:
Image -
the optical counterpart of a self-luminous or illuminated object
formed by the light rays that traverse an optical system made up of
a series of lenses; each point of the object has a corresponding point
in the image from which rays diverge or appear to diverge. This def-
inition holds true for optical systems using illuminating beams other
than light, such as electrons.
Imaging -
the formation of images of objects that can be created using
light (optical microscopy), lasers (confocal microscopy), electrons
(scanning and transmission electron microscopies) and scanned
molecular mechanical probes (atomic force microscopy).
Microscopy -
the interpretive application of magnifi cation created by
a microscope to the study of materials that cannot be seen properly
by the unaided eye.
Microscopes do not only magnify objects. A more important measurable
property of microscopes is their capability to resolve or clearly determine
two separate points, or objects, as singular, distinguished entities. This prop-
erty is known as microscope resolution. The lower resolution limit of a
microscope system decreases from microns to nanometers and angstroms
as an analyst goes from producing images with light rays to producing them
with electrons and scanned molecular mechanical probes. These image tech-
niques are shown in Table 1.1 together with the resolution relationships.
As the fi eld of biomedical engineering moves toward the ability to more
precisely engineer biomaterials, cells and tissue replacements there is an
increased necessity to image sub-micron details in a wide variety of specimen
types. The increased use of scanning electron microscopy (SEM), transmis-
sion electron microscopy (TEM) and atomic force microscopy (AFM) (each
with ever lower resolution limits) as a multi-technique integrated imaging
tool set has allowed the almost routine observation of important biologi-
cal and chemical phenomena such as cell-cell and cell-extracellular matrix
interactions, intracellular events and nano-scale changes in biomaterials.
Imaging using an integrated tool set of powerful microscopes is becom-
ing a critical component of the science of biomaterials characterization.
The almost routine use of these instruments allows both researchers and
engineers to fabricate new materials, coatings and devices; study both their
