KEYWORDS: Optical coherence tomography, 3D image processing, Electrodes, Mirrors, Visualization, Data acquisition, Bone, Signal to noise ratio, Surgery, OpenGL
In cochlear implant surgery, an electrode array is inserted into the cochlear canal to restore hearing to a person who is
profoundly deaf or significantly hearing impaired. One critical part of the procedure is the insertion of the electrode
array, which looks like a thin wire, into the cochlear canal. Although X-ray or computed tomography (CT) could be used
as a reference to evaluate the pathway of the whole electrode array, there is no way to depict the intra-cochlear canal and
basal turn intra-operatively to help guide insertion of the electrode array. Optical coherent tomography (OCT) is a highly
effective way of visualizing internal structures of cochlea. Swept source OCT (SSOCT) having center wavelength of 1.3
micron and 2D Galvonometer mirrors was used to achieve 7-mm depth 3-D imaging. Graphics processing unit (GPU),
OpenGL, C++ and C# were integrated for real-time volumetric rendering simultaneously. The 3D volume images taken
by the OCT system were assembled and registered which could be used to guide a cochlear implant. We performed a
feasibility study using both dry and wet temporal bones and the result is presented.
We demonstrated high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PSOCT)
using a single InGaAs line-scan camera and an optical switch at 1.3-μm region. The polarization-sensitive
low coherence interferometer in the system was based on the original free-space PS-OCT system published by
Hee et al. The horizontal and vertical polarization light rays split by polarization beam splitter were delivered
and detected via an optical switch to a single spectrometer by turns instead of dual spectrometers. The SD-PSOCT
system had an axial resolution of 8.2 μm, a sensitivity of 101.5 dB, and an acquisition speed of 23,496 Alines/s. We obtained the intensity, phase retardation, and fast axis orientation images of a biological tissue. In
addition, we calculated the averaged axial profiles of the phase retardation in human skin.
We propose high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) using a single camera and a 1×2 optical switch at the 1.3-µm region. The PS-low coherence interferometer used in the system is constructed using free-space optics. The reflected horizontal and vertical polarization light rays are delivered via an optical switch to a single spectrometer by turns. Therefore, our system costs less to build than those that use dual spectrometers, and the processes of timing and triggering are simpler from the viewpoints of both hardware and software. Our SD-PS-OCT has a sensitivity of 101.5 dB, an axial resolution of 8.2 µm, and an acquisition speed of 23,496 A-scans per second. We obtain the intensity, phase retardation, and fast axis orientation images of a rat tail tendon ex vivo.
We built a high-speed, real-time spectral domain optical coherence tomography (SD-OCT) system at the 1.3 μm region
using an InGaAs line-scan camera with 1024 pixels and 46.99 klines/s. In SD-OCT, the actual spatial resolution can be
different from the theoretical one due to the large bandwidth of the light source and the finite number of detector pixels,
especially for a long center wavelength. We calculated and compared the axial resolutions obtained from the point spread
function and the physical pixel size of the OCT image. We found that the axial resolution of the SD-OCT system could
be limited in the 1.3 μm region if the depth range becomes large.
We constructed a high-speed laser line-scanning confocal microscope (LSCM) using He-Ne laser (633 nm), a line CCD
camera, and an acousto-optic deflector (AOD). The line scanner consists of an AOD and a cylindrical lens, which create
a line focus sweeping over the sample. The line scanner generates two-dimensional confocal images (512× 512 pixel
image) up to 191 frames per second with no mechanically-moving parts. This system is configured as an inverted
microscope for imaging biological organisms or tissues. Images of various biological samples were obtained including
rabbit cornea, onion cells, mouse melanoma tumor cells (B16BL6), and human breast tumor cells (BT-20). The frame
rate may be further improved up to over 700 frames per second when the image size is reduced (512×128 pixel image).
This system may be useful for analyzing fast phenomena during biological and chemical interactions and for imaging 3D
structures rapidly.
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