Optical Characterization Of Vocal Folds By Oct-Based Laryngoscopy

Optical coherence tomography (OCT) is a new non-invasive method to investigate biological tissue. It is particularly suitable for examination of human vocal folds due to its optical penetration depth of around 1.5mm.We developed a modified laryngoscope with an integrated OCT beam path for non-contact imaging of human vocal folds. In vivo studies on awake patients show that synchronous OCT and conventional laryngoscopy works well. For enabling the choice of the appropriate OCT encoding technique for OCT-based laryngoscopy measurements on simulated vibrations were performed with time domain (TD) and fourier domain (FD) OCT devices. The results shoe, that TD-OCT is much more suitable for non-contact imaging than FD-OCT.In studies on porcine and monkey vocal folds the performance of femtosecond laser tissue ablation was analyzed with OCT monitoring. Histopathological sections could be well correlated with the OCT images. In future applications a combined system that uses one femtosecond laser as light source for tissue ablation as well as for OCT imaging is conceivable.In conclusion, OCT can be used as a pre-, intra- and postoperative diagnostic instrument for analysing the vocal fold structure down to the vocalis muscle allowing a more precise indication for potential subsequent invasive procedures. We suggest that OCT should be used in addition to established examination methods for diagnostic evaluation of vocal fold malignancies and functional alterations.