X-ray image enhancement based on the dyadic wavelet transform

摘要

X-ray images are often of low contrast due to the subtle distinction of attenuatioin coefficients and scatter effect, which makes it diffcult to distinguish signals for background. This paper proposes an image enhancement algorithm using the multi-scale dyadic wavelet transform. The algorithm includes two steps:1)In order to enhance contrast, a non-linear mapping is performed on wavelet coefficients at different scales. Inhibition factors are then applied to reduce the impact of scatter;2)In order to reduce the negative impact of noise amplification from the first step, wavelet coefficients, and then filtered with different schemes for eachcategories:irregular coefficients and edge-related and regular coefficients, and the filtered with different schemes for each category. Experimental results demonstrate that this algorithm effectively enhance the contrast of X-ray images. Examination is also done on CT reconstructioins from multi-view projection date processed by the proposed method and significant improvement of image quality is observed. Our results are expected to offer grat help to follow-up detection and recognition tasks.