Color masking improves classification of celiac disease in videocapsule endoscopy images.

BACKGROUND: Videocapsule endoscopy images are useful to detect pathologic alterations, including villous atrophy, in the small intestinal mucosa, which is helpful for diagnosing celiac disease. In prior work, quantitative videocapsule analysis was found useful to classify celiac versus control images. However, the effect of dark/extraneous substances on classification efficacy requires remediation.

METHOD: For quantitative analysis, data from the Medtronic SB2 and SB3 systems were pooled. Videocapsule images of the distal duodenum/proximal jejunum were acquired from 13 celiac and 13 control patients. Dark regions, extraneous fluids, and air bubbles were mostly removed by utilizing color masking. Two different red-green-blue (RGB) color masks were constructed from 20 to 30 reference pixels obtained from mucosal and from extraneous regions. Each image pixel was accepted or rejected for subsequent analysis based on whether its distance was closest to a mucosal or to an extraneous reference in RGB space. Four images were then randomly selected from each videoclip for processing (52 images from each group). After masking, celiac versus control images were plotted in a three-space consisting of mean and standard deviation in pixel brightness, and surface area remaining after masking. A linear discriminant function was used for classification. The paradigm was repeated with a second random data set for validation.

RESULTS: Masking improved classification of celiac versus control images to nearly 80% accuracy as compared to 70-77% without masking. Celiac disease patients tended to have lesser mean pixel brightness and greater variability in brightness, in accord with prior work, and more masking was needed to remove extraneous features.

CONCLUSIONS: Color masking is useful to remove dim/extraneous features from videocapsule images and it results in improved classification/assessment to distinguish celiac with villous atrophy from control videocapsule image. This can be helpful to detect and map regions of pathology, to screen for celiac disease, and to determine the efficacy of a gluten free diet.