Classification of melanoma using tree structured wavelet transforms

Modern Techniques for Computer-Aided Melanoma Diagnosis

“…In the end with opening/closing operations (and binarization when required) we got an output form of the lesion image. The preparation stage for the wavelet%based features (Patwardhan et al 2003(Patwardhan et al , 2005) (Surówka et al 2006) was done in the following way: Since the wavelet decomposition downscales the input image by a factor of 2 in rows or columns every iteration, the width and length had to be powers of 2, so the source images were filled with black pixels in due number of rows and columns. In order to apply any transform on the picture, the compressed image (JPG) must be changed into a 2D matrix of numbers.…”

“…Performance of the wavelet analysis of images depends on various factors: • For feature extraction it is important to choose between recursive decomposition of the low%frequency branch (Mallat 1989) (the pyramidal algorithm) and, on the other hand, a more selective tree%structured analysis where the further decomposition is applied to the output of any channel (Patwardhan et al 2003, Chang et al 1993). The latter is advocated by observations that the significant sub%bands of the pigmented skin texture are those in the middle frequency range (Patwardhan et al 2003(Patwardhan et al , 2005).…”

“…The latter is advocated by observations that the significant sub%bands of the pigmented skin texture are those in the middle frequency range (Patwardhan et al 2003(Patwardhan et al , 2005). …”

“…Both representations have advantages and disadvantages. Unfortunately, up to now only a limited number of the aforementioned possibilities have been tested on skin dermoscopic textures (Patwardhan et al 2005, Patwardhan et al 2003, Surówka et al 2006. Since skin textures are signals consisting mainly of middle frequency bands it has been shown that the most adequate approach to the wavelet%based multiresolution analysis is the concept of wavelet packets (Chang et al 1993).…”

Analysis of the contour structural irregularity of skin lesions using wavelet decomposition

“…In the previous decade, there have been many studies concerning the boundary irregularity of lesions using both geometric [7,8,9,10] and local fractal [11] measures. There are two types of irregularities found on boundaries: textual and structural, these correspond to fine changes and obvious convex and concave features respectively [7].…”