Optical coherence tomography (OCT) is a promising candidate for monitoring the bottom of the drilled channel during
cochleostomy to prevent injury to the critical structure under the bone tissue. While the thickness of the overlaying bone
tissue is changed during the drilling process, the wave front of the backscattered light is also altered, resulting in
changing speckle patterns of the observed structures in the sequential historical scans. By averaging the different patterns
in these scans, named history compounding, the speckles can be reduced and the detection of critical structure becomes
much easier. Before averaging, the refractive index of bone tissue 𝑛𝑏 has to be compensated so that the speckles of the
same structure in different historical scans can be aligned together. An accurate method for measuring the refractive
index nb using OCT is presented. Experiments were conducted to evaluate history compounding and the new technique
is proved to be an effective, flexible and intuitive speckle reduction technique for OCT guided cochleostomy as well as
hard tissue ablation of other kind.
While using a laser to process hard tissue, it is difficult to guarantee, that the laser beam is always perpendicular to the
tissue surface. Therefore, it is necessary to know the dependence of ablation depth on angle of incidence for preoperative
planning. Considering the propagation of the ablation front, an Addition Model is developed in this work. It indicates
that the shape of a crater ablated by a single pulse with non-zero angle of incidence can be regarded as the sum of the
original tissue surface and a symmetric profile, which is corresponding to the shape of a crater ablated by
perpendicularly incident beam. Meanwhile, the ablation depth at a point P is defined as the distance from P to the
original tissue surface along the optical axis of the incident beam. In the context of this definition, the dependence is
experimentally studied. The results of the experiments were unexpected: the ablation depth is independent of angle of
incidence up to ca. 55°. Possible reasons for these results are discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.