Thickness determination of melanocytic nevi by means of optical coherence tomography

authored by

Arthur Varkentin

supervised by

Bernhard Wilhelm Roth

Abstract

This thesis presents a fast, reliable, and non-invasive method for in vivo thickness determination of melanocytic nevi, and melanomas in particular. Such a tool is highly desirable for clinical dermatology as it may facilitate the identification of surgical melanoma margins, determine if a sentinel node biopsy should be performed or not, and, thus, reduce the number of surgical interventions for patients. In this work, optical coherence tomography (OCT) is evaluated for quantitative in vivo preoperative assessment of the melanocytic skin infiltration depth. Comparison with the Breslow tumor thickness obtained from subsequent histopathology as the gold standard reveals that non-invasive OCT can determine the infiltration depth of melanocytic lesions preoperatively and in vivo with an accuracy comparable to invasive histopathology measurements on skin biopsies. Moreover, OCT can produce volumetric images of the lesion giving access to lateral and axial dimensions after applying an image segmentation algorithm. Successive OCT measurements allow for growth tracking of the invisible parts below the skin surface and the evolution of the lesion infiltration depth. In addition, a multimodal measuring device for rapid, noninvasive in vivo skin cancer screening is presented, combining three optical modalities: OCT and optoacoustics (OA) to provide precise tumor depth determination with a Raman spectroscopic modality capable of detecting the lesion type and, thus, providing diagnostic capability. Both setups, OA and Raman, use wide field skin illumination to ensure compliance with Maximum Permissible Exposure (MPE) requirements for clinical use. The Raman signal is collected via the OCT scanning lens to maximize the signal-to-noise ratio (SNR) of the measured signal. OCT is used to optically determine the tumor thickness and for volumetric imaging whereas optoacoustics utilizes acoustic signals generated by optical absorption contrast for thickness determination at potentially higher penetration depths compared to OCT. Results of first clinical trials using the described setup are also presented in this work. The measured lesion depth is in good agreement with histology results, while Raman measurements show distinctive differences between normal skin and melanocytic lesions, and, moreover, between different skin areas. For future work, approaches are discussed to validate the setup for reliable detection of pathophysiological parameters, morphology and thickness of suspicious skin lesions.

Organisation(s)

Hannover Centre for Optical Technologies (HOT)
Institute of Quantum Optics

Type

Doctoral thesis

No. of pages

172

Publication date

2018

Publication status

Published

Sustainable Development Goals

SDG 3 - Good Health and Well-being

Electronic version(s)

https://doi.org/10.15488/3419 (Access: Open)