Two commonly used HSI techniques are spatial scanning and spectral scanning.
In aspatial scanningmethod,first a complete continuous spectrum is obtained for
an individual pixel in a 2D tissue sample and then the sample is scanned pixel by
pixel to create a hypercube dataset, which consists of two spatial dimensions and
one spectral dimension. In thespectral scanningmethod,first the entire 2D sample
is scanned for a specific wavelength and then the system steps through a wave-
length range to obtain the hypercube.
10.7 Summary
Light-based biomedical imaging technologies have greatly extended the ability for
the non-invasive imaging and diagnoses of diseases in humans. In addition to the
advances in microscopic and spectroscopic technologies described in the previous
two chapters, photonics-based methodologies such as optical coherence tomogra-
phy, miniaturized endoscopic processes, laser speckle imaging, optical coherence
elastography, photoacoustic tomography, and hyperspectral imaging have emerged
in biophotonics applications.
10.8 Problems.
10 :1 Consider an imaging system that records 1000 points in each 3D direction.
If the line scans are carried out at rates of 100 kHz, show that the
two-dimensional B-scans are recorded at rates of 100 frames per second and
that the volume C-scans are done at rates of 0.1 volume per second, so that a
volume C-scan takes 10 s.
10 :2 Consider an imaging system that records 1000 points in each 3D direction.
If the line scans are carried out at rates of 1 MHz, show that a volume
C-scan is done in 1 s.
10 :3 From Eq. (10.4), derive the intensity expression IDat the detector of the
light beams coming from the two arms of the interferometer as given by
Eq. (10.5).
10 :4 Suppose an OCT setup for ophthalmology tests uses the following
super-luminescent diodes: an 800-nm peak wavelength with a 25-nm
spectral bandwidth and a 1300-nm peak wavelength with a 70-nm spectral
bandwidth for the posterior segment and the anterior segment of the eye,
respectively. Show that the coherence lengths of these two sources are 25.6
and 24.1μm, respectively.
10 :5 Consider the following super-luminescent diodes: an 800-nm peak wave-
length with a 25-nm spectral bandwidth and a 1300-nm peak wavelength10.6 Hyperspectral Imaging 317