Patients and images
A total of 12 patients undergoing endoscopic resection of middle ear cholesteatoma were prospectively enrolled in the present study. All patients provided informed consent and the study was approved by the local ethical committee (Kantonale Ethikkommission Bern KEK2019-00555). At the end of the cholesteatoma resection a final endoscopic check for residual disease is routinely performed. During this complete check of the middle ear, zones with residual tissue (cholesteatoma, granulation tissue, but not macroscopically normal mucosa) were photographed using the three DIE modalities clara (normal image), spectra A and spectra B as illustrated in Figure 1. Light intensity standardized to 70% for every imaging modality (PowerLED300, Karl Storz, Tuttlingen, Germany).
Thereafter the photographed tissue was removed and sent for separate histopathological evaluation. From the histopathological analysis 10 sites of residual cholesteatomatous tissue and 10 sites of non-cholesteatomatous tissue (e.g. granulation tissue, mucosa) were selected. Accordingly, 20 different surgical sites provided the final set of 60 images (each site registered with 3 different image modalities) representing residual cholesteatoma or residual granulation tissue for further analysis.