Biomedical Engineering Reference
In-Depth Information
(a)
(b)
Z
Z
Y
X
1.0 mm
Y
X
1.0 mm
(c)
Z
X
Y
1.0 mm
FIGURE 3.5
Micro-CT images of (a) PLLA scaffold with pore size of 255-350 µm, (b) fi brous chitosan
scaffold with fi ber diameter around 105 µm and porosity of 85%, and (c) fi brous chitosan scaffold with fi ber
diameter around 65 µm and porosity of 95%.
to indicate the densest material under investigation, in this instance, PLLA and chitosan. So pores
occupy the remaining volume within the volume of interest (VOI). The porosity is calculated by
subtracting the percentage of polymer out of the total volume. The clearly characterized morphology
of the fi brous and porous scaffolds is shown in Figure 3.5. In addition, the quantitative data such as
pore size and porosity can be easily derived from it.
3.5.2.2
Optical Coherence Tomography
An all-fi ber time-domain OCT, based on a Michelson interferometer, was used for the study
(Figure 3.6). The detailed description of the system can be found elsewhere.
150
Briefl y, the system
employed a 1300 nm superluminescent diode with a bandwidth of 52 nm, which was coupled into
the port 1 of a circulator. A 50/50 fi ber coupler splits the beam from port 2 to the reference and sam-
ple arms. Port 3 is connected to the balanced detector for heterodyne detection. The signal-to-noise
ratio (SNR) of the system is measured at 90 dB with the use of a 4-OD neutral density fi lter with a
scanning speed of 100 Hz. The depth-scan was performed by a double-pass grating-based scanning
system to scan rapidly the optical delay in the reference arm. The measurement beam was scanned
over the sample by a mirror controlled by the galvanometer. The system has a measured
x
-
z
resolu-
tion of 16 µm
µm in free space. The scans presented in this study were scaled according to a
mean refractive index of 1.4, commonly adopted for biological material. A linear
x
-
y
stage has been
equipped to collect successive scans, allowing a 3-D reconstruction of the sample images. The step
of successive scans was chosen as 25 µm.
×
14
