In tissue engineering, where the goal is to create artificial structures that mimic living organs such
as skin or bone, researchers frequently use a scaffold-based approach. Scaffolds,
which help support and bind the cellular elements of the tissue being created, are
designed and fabricated to have the architectural properties required by the ultimate
mimetic purpose of the tissue, and there are a number of ways to inspect and characterize
these properties, including microcomputed tomography.
The mechanical strength and biological
functionality of an artificial tissue scaffold is determined by its architectural
and structural properties, which include the ratio of surface area to volume, porosity,
interconnectivity, pore size, strut and/or wall thickness, cross-sectional area,
permeability, and directionality and alignment of the struts. Besides microcomputed
tomography, methods of testing these properties have included theoretical calculation,
scanning electron microscopy, mercury and flow porosimetry, gas pycnometry and gas
adsorption.
Now Saey Tuan Ho and Dietmar W. Hutmacher
of the National University of Singapore have provided an overview of how microcomputed
tomography compares with the other methodologies. They explain the importance of
the architectural and structural properties of scaffolds and describe the role each
measurement technique plays in the characterization of scaffolds, especially regarding
porosity.
The authors also describe two applications
of microcomputed tomography: one in which it evaluated polymer scaffolds produced
via rapid prototyping and one in which it analyzed fine, flexible scaffold meshes.
They concluded that, although a relatively
new technique, microcomputed tomography has considerable advantages over other methods:
It is a noninvasive approach that can calculate several parameters at once. It is,
however, hampered by beam hardening — an effect of the scaffold material’s
attenuation of the CT’s low-energy x-rays, resulting in high exposure at the
center of the scaffold — and by increased difficulty with image processing
because of thresholding complications. (Biomaterials, March 2006, pp. 1362-1376.)