Phase Unwrapping Problems in Digital Holographic Microscopy of Biological Cells - Biomedical Optical Phase Microscopy and Nanoscopy - page 139

(A) (B) (C)

1333

nm

0

(D)

Figure 7.12
Confluent SKOV-3 ovarian cancer cells: (A) amplitude image, (B) reconstructed phase for
λ 5 532 nm, (C) dual-wavelength coarse phase image, and (D) 3D rendering of fine map. All

images are 92 μ m 92 μ m (240 240 pixels). The area at the bottom of the images is the

exposed part of the gold substrate.

3 3

The dual-wavelength phase imaging method has been applied to 3D imaging of ovarian
cancer cells (SKOV-3) [3] . Figure 7.12A shows the intensity image of a confluent group of
cells, which is similar to what one can see using an ordinary microscope. Figure 7.12B
displays a single wavelength wrapped phase image, Figure 7.12C shows the coarse dual-
wavelength unwrapped phase image, and Figure 7.12D displays 3D rendering of the final
low noise “fine” map. To measure the physical thickness of cells by using Eq. (7.5) ,we
need to make an assumption of the cell's refractive index, n 5 1.375. Note that while it may
not be possible to precisely determine the refractive index of the cell at each individual
point, this number is always very close to the refractive index of water.

Figure 7.13 shows the image of a single (SKOV-3) cell, where the cell's nucleus and
pseudopodia are clearly seen. By using the phase to thickness conversion ( Eq. (7.5) ), we
can determine the 3D features of the cell. Figure 7.13D displays the line height profile,
which indicates, for example, that the overall cell height is about 1.47 μ m, with the

thickness of the cell's pseudopodia (lamelipodia) at around 270 nm.