血管内超声图像的血液噪声抑制和对比度增强研究

提出基于二进小波变换的血管内超声图像血液斑点噪声抑制和对比度增强算法。根据血管内超声成像的特点估计噪声的方差，并由二进小波变换的分解结构给出局部阈值的计算方法，结合软阈值滤波法和硬阈值滤波法对不同尺度的小波系数进行萎缩处理。同时采用了基于多尺度边缘表示的，利用小波系数极值拉伸和Hermite多项式插值实现的快速增强算法。实验结果表明，与现有血管内超声图像去噪的方法相比，该方法在抑制血液斑点噪声的同时增强了图像对比度，保留了图像的细节，具有更好的实用性。

Noise Reduction and Contrast Enhancement of Intravascular Ultrasound Images

An algorithm based on dyadic wavelet transform for speckle reduction and contrast enhancement in intravascular ultrasound images was presented. Noise variance was estimated according to characters of IVUS images, a method to estimate local threshold was proposed based on decomposed structure of dyadic wavelet transform and soft thresholding was combined with hard thresholding when smoothed images . In addition, an fast contrast enhancement algorithm based on multi-scale edges representation of images through stretching the local extrema and interpolating them with Hermite interpolation polynomials was carried out. Experiments with clinical images showed that this algorithm was capable of not only reducing the speckle noise of blood but also enhancing features of diagnostic importance of intravascular ultrasound images and produced superior results qualitatively when compared to results obtained from existing denoising methods alone.