Abstract. 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.

Abstract. We present a time-resolved photographic analysis of the pulse-to-pulse interaction. In particular, we studied the influence of the cavitation bubble induced by a fs-pulse on the optical focusing of the consecutive pulse and its cavitation bubble dynamics in dependence on temporal pulse separation in water. As a first result, by decreasing the temporal separation of laser pulses, there is a diminishment of the laser-induced optical breakdown (LIOB) efficiency in terms of energy conversion, caused by disturbed focusing into persisting gas bubbles at the focal volume. A LIOB at the focal spot is finally suppressed by impinging the expanding or collapsing cavitation bubble of the preceding pulse. These results could be additionally confirmed in porcine gelatin solution with various concentrations. Hence, the interaction between the laser and transparent ophthalmic tissue may be accompanied by a raised central laser energy transmission, which could be observed in case of a temporal pulse overlap. In conclusion, our experimental results are of particular importance for the optimization of the prospective ophthalmic surgical process with future generation fs-lasers.

N/A. Laryngoscope, 126:E332-E336, 2016.

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