Spatial and Spectral Calibration of a Multispectral-Augmented Endoscopic Prototype

International audienceWe developed a multispectral-augmented endoscopic prototype which increases the common number of bands under analysis, allowing exploration in the visible and near infrared range (400–1000 nm). The prototype combines endoscopy with spectroscopy using white light (WL) or Narrow Band Imaging light (NBI) endoscope and two multispectral cameras connected to a twin-cam splitter. The splitter is then connected to an optical fiber and introduced in the endoscope instrument channel.In this work, we introduce a spectral calibration and an axial displacement correction function to register both modalities. The former is based on a multi-linear transformation of multispectral bands and its performance is assessed using a Digital SG ColorChecker® pattern to report an RMSE of 6.78%. The latter relates the insertion depth of the fiberscope with the required geometric transformation. The performance was assessed using a chessboard pattern and its corner coordinates as ground truth. The mean RMSE error for the registration using our method was 2.3 ± 0.7 pixels, whereas the RMSE error using a frame by frame homographic registration was 1.2 ± 0.4 pixels. Finally, the technique was tested on mouth exploration samples to simulate in-vivo acquisition and display complete spectra for single points of analysis. The results reveal that our method provides similar performance when compared to a homographic transformation which would be impossible to perform in-vivo

Identification of precancerous lesions by multispectral gastroendoscopy

International audienc

Supplementary Material for: Endoscopic features of synchronous multiple early gastric cancers: Findings from a nationwide cohort

Introduction: We investigated the factors associated with synchronous multiple early gastric cancers and determined their localization. Methods: We analyzed 8191 patients who underwent endoscopic submucosal dissection for early gastric cancers at 33 hospitals in Japan from November 2013 to October 2016. Background factors were compared between single-lesion (n=7221) and synchronous multi-lesion cases (n=970) using univariate and multivariate analyses. We extracted cases with two synchronous lesions (n=832) and evaluated their localization. Results: Significant independent risk factors for synchronous multiple early gastric cancer were older age (≥75 years old) (OR=1.257), male sex (OR=1.385), severe mucosal atrophy (OR=1.400), tumor localization in the middle (OR=1.362) or lower region (OR=1.404), and submucosal invasion (OR=1.528 (SM1), 1.488 (SM2)). Depressed macroscopic type (OR=0.679) and pure undifferentiated histology OR=0.334) were more common in single early gastric cancers. When one lesion was in the upper region, the other was more frequently located in the lesser curvature of the middle region. When one lesion was in the middle region, the other was more frequently located in the middle region or the lesser curvature of the lower region. When one lesion was in the lower region, the other was more frequently located in the lesser curvature of the middle region or the lower region. Conclusion: Factors associated with synchronous multiple early gastric cancer included older age, male sex, severe mucosal atrophy, tumor localization in the middle or lower region, and tumor submucosal invasion. Our findings provide useful information regarding specific areas that should be examined carefully when one lesion is detected