“…[30][31][32][33]. Principal component analysis (PCA) by [30], Median filtering [6][7][8]21,27], Gabor filter [6][7][8]17,27,34], multi-scale selective filter [24], Gaussian filter, average filter, and disk filter [35], Auto-enhancement algorithm and Fast Fourier transform (FFT) [17], erosion, and dilation [21], isotropic re-sampling, tri-linear interpolation [10,36], linear interpolation algorithm [25,37], contrast enhancement [11,14], thresholding, blob analysis [11], template modeling [38], adaptive thresholding [39], background thresholding [40], and mass screening and edge preserving smoothness [41] are found to be suitable for medical images. These are used to remove noise, enhance the image quality, and detect boundary of lung region to be useful for further steps.…”