Evaluation of histogram enhancement techniques used in conjunction with wavelet compression methods for improved signal processing of child trauma images

The performance of wavelet compression techniques, in conjunction with enhancement methods like histogram normalization, is evaluated in this paper for a child trauma emergency case. The compression techniques are applied to original CT digitized images as well as to enhanced images. The processing of the images consists of alternative application of enhancement and compression techniques. The criteria used for rating the results are both subjective and objective. The evaluation based on objective criteria is comparable to the evaluation based on subjective criteria, as far as the original images are concerned. Despite the fact that the relative Mean-Square-Error (MSE) of the enhanced images as compared to the original images is slightly worse for the same compression ratio, the rating according to subjective criteria indicates better results for the enhanced images. The expert observers view more diagnostic information in the enhanced images rather than in the original ones. Furthermore, enhancing original images after compression yields higher MSEs than vice versa. Other operators in medical image processing are to be investigated in the future in order to determine the optimum operator, which retains the diagnostic information and, at the same time, assures the best compression using wavelets.