Tham khảo tài liệu 'new developments in biomedical engineering 2011 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 192 New Developments in Biomedical Engineering other conventional methods. AUC increased from to with improvement of tumor extraction algorithm. When the diagnostic threshold was defined at a sensitivity of 80 our extraction method showed approximately 20 better accuracy in specificity. Feature extraction from the image After the extraction of the tumor area the tumor object is rotated to align its major axis with the Cartesian x-axis. We extract a total of 428 image related objective features Iyatomi et al. 2008b . The extracted features can be roughly categorized into asymmetry border color and texture properties. In this section a brief summary is described please refer the original article for more details. a Asymmetry features 80 features We use 10 intensity thresholds values from 5 to 230 with a stepsize of 25. In the extracted tumor area thresholding is performed and the areas whose intensity is lower than the threshold are determined. From each such area we calculate 8 features area ratio to original tumor size circularity differences of the center of gravity between original tumor standard deviation of the distribution and skewness of the distribution. b Border features 32 features We divide the tumor area into eight equi-angle regions and in each region we define an SB X SB window centered on the tumor border. In each window a ratio of color intensity between inside and outside of the tumor and the gradient of color intensity is calculated on the blue and luminance channels respectively. These are averaged over the 8 equi-angle regions. We calculate four features for eight different window sizes 1 5 1 10 1 15 1 20 1 25 1 30 1 35 and 1 40 of the length of the major axis of the tumor object L. c Color features 140 features We calculated minimum average maximum standard deviation and skewness value in the RGB and HSV color spaces respectively subtotal 30 for the whole tumor area perimeter of the tumor area differences between the tumor area .
