一种改进的基于模型的迭代重建算法对双源CT扫描仪图像纹理和视觉效果的影响
Effect of an advanced model-based iterative reconstruction algorithm on texture and visual impression of images privieded by a dual source CT scanner
摘要：
目的：评估ADMIRE算法对图像纹理和图像视觉印象的影响，作为噪声水平和空间分辨率等常见图像质量参数测量的补充。方法：在不同的辐射剂量水平下对ACR体模进行了检查。为了表征图像纹理，评估了不同剂量水平和重建算法的两个Haralick纹理参数，对比度和熵。使用结构相似性指数（SSIM）评价图像的视觉印象及其结构差异。确定所有剂量和AMIRE水平的噪声，并与滤波反投影（FBP）进行比较。空间分辨率由调制传递函数和线扩展函数决定。结果如下：Haralick纹理参数随着ADMIRE水平I的增加而降低，直到V. ADMIRE III，IV和V提供了与由FBP计算的那些具有高达50%的辐射剂量减少的对比度和熵。SSIM随着ADMIRE水平的增加而改善。通过ADMIRE IV和V计算的SSIM通过滤波器反投影显示出相似的值，剂量降低高达50%。空间分辨率保持高达90%的剂量减少。随着ADMIRE和剂量水平的增加，噪声分布向更窄的分布移动，这与使用ADMIRE的重建图像一致。结论：纹理分析和SSIM允许比仅基于噪声分布或空间分辨率的物理测量的质量度量更真实地评估迭代重建算法的剂量降低潜力。这项工作表明，通过ADMIRE算法，可以在减少辐射剂量的情况下达到相当的图像质量。
英文摘要：
Purpose: To evaluate the influence of ADMIRE algorithm on image texture and image visual impression as a supplement to measurements of common image quality parameters such as noise levels and spatial resolution. Methods: An ACR phantom was examined at different radiation dose levels. To characterize the image texture, two Haralick texture parameters, contrast and entropy, for different dose level and reconstruction algorithms were assessed. The visual impression of images and their structural differences were evaluated using the structural similarity index (SSIM). Noise was determined for all dose and AMIRE levels and compared to those by filtered back projection (FBP). The spatial resolution was determined by the modulation transfer functions and the line spread function. Results: The Haralick texture parameters decreased with increasing ADMIRE levels I up to V. ADMIRE III, IV and V offered a comparable contrast and entropy to those calculated by FBP with a radiation dose reduction up to 50%. SSIM improved with increasing ADMIRE levels. SSIM calculated by ADMIRE IV and V showed similar values by the filter back projection with a dose decrease up to 50%. Spatial resolution was retained up to 90% dose reduction. With increasing ADMIRE as well as dose level the noise distribution shifted to a more narrow distribution, which was in accordance with the reconstructed images using ADMIRE. Conclusion: Texture analysis and SSIM allow a more realistic assessment of the dose reduction potential of iterative reconstruction algorithms than quality metrics only based on physical measurements of noise distribution or spatial resolution. This work presented that by means of the ADMIRE algorithm, a comparable image quality at reduced radiation doses can be reached.
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