Computer-aided grading system for endoscopic severity in patients with ulcerative colitis

The degree of mucosal redness can be quantified as an index of hemoglobin (IHB) that changes with photographic conditions. The first aim of the present study was to stress the exclusion of γ correction as a critical procedure for reliable measurements of IHB. The second aim was to characterize Matts grade by pictorial parameters in the gray scale picture of IHB and to establish a computer-aided grading system of endoscopic severity in ulcerative colitis. A total of 130 digital endoscopic pictures of 55 patients with ulcerative colitis (30 Matts 1, 70 Matts 2, 20 Matts 3 and 10 Matts 4) were used. The pictures without γ correction were processed for the mean IHB, SD of IHB, kurtosis of IHB and contrast feature. A computer-aided grading system was constructed on the basis of Bayes decision theory. Significant increase in the mean IHB was seen when comparing Matts 1 to Matts 2. The SD of IHB or contrast feature significantly increased from Matts 2 to Matts 3 or from Matts 3 to Matts 4. Kurtosis of IHB was significantly larger in Matts 3 than in Matts 1 or Matts 4. Sensitivity and specificity when discriminating Matts 1 from Matts 2, Matts 2 from Matts 3 and Matts 3 from Matts 4 by the grading system were found to be 84 and 96%, 94 and 70%, and 100 and 85%, respectively. The computer-aided grading system may permit quantitative evaluation of effects of treatments in ulcerative colitis with minimal interobserver variation.