Optical coherence tomography (OCT) provides structural information of laryngeal tissue which is comparable to histopathological analysis of biopsies taken under general anesthesia. In awake patients, movements impede clinically useful OCT acquisition. Therefore, an automatic compensation of movements was implemented into a swept source OCT-laryngoscope. Video and OCT beam path were combined in one tube of 10-mm diameter. Segmented OCT images served as distance sensor and a feedback control adjusted the working distance between 33 and 70 mm by synchronously translating the reference mirror and focusing lens. With this motion compensation, the tissue was properly visible in up to 88% of the acquisition time. During quiet respiration, OCT contrasted epithelium and lamina propria. Mean epithelial thickness was measured to be 109 and 135 μm in female and male, respectively. Furthermore, OCT of mucosal wave movements during phonation enabled estimation of the oscillation frequency and amplitude. Regarding clinical issues, the OCT-laryngoscope with automated working distance adjustment may support the estimation of the depth extent of epithelial lesions and contribute to establish an indication for a biopsy. Moreover, OCT of the vibrating vocal folds provides functional information, possibly giving further insight into mucosal behavior during the vibratory cycle.
Optical coherence tomography (OCT) is an imaging technique which enables diagnosis of vocal cord tissue structure by
non-contact optical biopsies rather than invasive tissue biopsies. For diagnosis on awake patients OCT was adapted to a
rigid indirect laryngoscope. The working distance must match the probe-sample distance, which varies from patient to
patient. Therefore the endoscopic OCT sample arm has a variable working distance of 40 mm to 80 mm. The current
axial position is identified by automated working distance adjustments based on image processing. The OCT reference
plane and the focal plane of the sample arm are moved according to position errors. Repeated position adjustment during
the whole diagnostic procedure keeps the tissue sample at the optimal axial position. The auto focus identifies and
adjusts the working distance within the range of 50 mm within a maximum time of 2.7 s. Continuous image stabilisation
reduces axial sample movement within the sampling depth for handheld OCT scanning. Rapid autofocus reduces the
duration of the diagnostic procedure and axial position stabilisation eases the use of the OCT laryngoscope. Therefore
this work is an important step towards the integration of OCT into indirect laryngoscopes.
Optical coherence tomography (OCT) is a non-invasive imaging technique which can create optical tissue sections, enabling diagnosis of vocal cord tissue. To take full advantage from the non-contact imaging technique, OCT was adapted to an indirect laryngoscope to work on awake patients. Using OCT in a handheld diagnostic device the challenges of rapid working distance adjustment and tracking of axial motion arise. The optical focus of the endoscopic sample arm and the reference-arm length can be adjusted in a range of 40 mm to 90 mm. Automatic working distance adjustment is based on image analysis of OCT B-scans which identifies off depth images as well as position errors. The movable focal plane and reference plane are used to adjust working distance to match the sample depth and stabilise the sample in the desired axial position of the OCT scans. The autofocus adjusts the working distance within maximum 2.7 seconds for the maximum initial displacement of 40 mm. The amplitude of hand tremor during 60 s handheld scanning was reduced to 50 % and it was shown that the image stabilisation keeps the position error below 0.5 mm. Fast automatic working distance adjustment is crucial to minimise the duration of the diagnostic procedure. The image stabilisation compensates relative axial movements during handheld scanning.
Biocompatibility studies of percutanous implants in animal models usually involve numerous lethal biopsies for
subsequent morphometric analysis of the implant-tissue interface. A common drawback of the study protocol is
the restriction of the analysis to one final time point. In this study optical coherence tomography (OCT) was used
to visualize and enable quantification of the local skin anatomy in the vicinity of a percutaneous implant in an
animal model using hairless mice. Non invasive in vivo optical biopsies were taken on predetermined time points
after implantation and ex vivo in situ at the day of noticeable inflammation. The custom made Fourier-domain
OCT system was programmed for imaging with different scanning schemes. A spoke-pattern of 72 cross-sectional
scans which was centred at the midpoint of the circular shaped implants was acquired and worked best for the
in-vivo situation. Motion-artefact-free three-dimensional tomograms were obtained from the implant site before
excision and preparation for histology. Morphometric parameters such as epithelial downgrowth, distance
to normal growth and tissue thickness were extracted from the images with a simple segmentation algorithm.
Qualitatively, the OCT B-Scans are in good agreement with histological sections. Therefore, OCT can provide
additional valuable information about the implant-tissue interface at freely selectable time points before the
lethal biopsy. Locally confined quantitative assessments of tissue-implant interaction for in vivo postoperative
monitoring can be carried out.