Optical Coherence Tomography: Technical Aspects - Biomedical Optical Imaging Technologies: Design and Applications - page 163

Fig. 5.1 Comparison of OCT with other clinical imaging modalities in terms of their resolution
and penetration depth

returning photon signals, OCT can perform both spectroscopic and polarization
imaging to better evaluate the composition of tissues and lesions. Moreover, the use
of fiber optics and its ability to integrate with medical catheters, surgical guiding
systems like endoscopes, and microscopes make it much easier to observe internal
structures through OCT, and also widening its clinical application scope to several
areas. With other technology to aid the development of OCT, doctors can actually
use OCT not only on the body but within the body. Figure 5.1 shows that OCT fills
the gap between the optical microscopy and the currently available clinical imaging
modalities in terms of imaging depth and resolution.
There are many important advantages to OCT over other existing clinical
imaging modalities, making it an important new complementary medical imaging
tool. It is minimally invasive, noncontacting, and nonionizing and has very high
spatial resolution and sensitivity and high speed and real-time data acquisition.
The basic setup can be extended to obtain measurement based on the functional,
polarization, spectroscopic, and other tissue parameters.

5.2 Low-Coherence Interferometry

As mentioned in Sect. 5.1 , OCT uses the interferometric detection and correlation
method to measure the echo time delay of backscattered light with high dynamic
range and sensitivity. The basic building block of OCT is based on a Michelson
interferometer (or its variant) with a low-coherence optical source, and this scheme
is generally called low-coherence interferometry or white light interferometry. In
LCI, low-coherence light reflected from the sample is used to provide information
on the time-of-flight (echo time delay) from refractive boundaries and backscattered