A post-reconstruction method to correct cupping artifacts in cone beam breast computed tomography
A post-reconstruction method to correct cupping artifacts in cone beam breast computed tomography
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DOI：
10.1118/1.2748106
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发表时间：
2007-07-01
期刊：
影响因子：
3.8
通讯作者：
Wang, T.
中科院分区：
文献类型：
--
作者：
Altunbas, M. C.;Shaw, C. C.;Wang, T.
在锥形束乳腺计算机断层扫描 (CT) 中，散射辐射会导致 CT 数字不均匀偏差，称为拔罐伪影。除了视觉干扰之外，杯形伪影还表现为背景不均匀性，这会损害有效的灰度窗口，并在基于阈值的体积可视化/分割中带来问题。为了克服这个问题，我们开发了一种专为锥形束乳腺CT设计的背景不均匀性校正方法。通过这种技术，拔罐伪影被建模为重建乳房图像中的附加背景信号轮廓。由于典型乳房的形状很大程度上是圆形对称的，所以附加背景信号轮廓也被假设为圆形对称的。通过测量前视乳房图像中脂肪组织信号的空间变化来估计背景信号的径向变化。为了以自动方式提取脂肪组织信号，实施了极坐标信号采样方案和背景趋势拟合算法。背景与目标脂肪组织信号值（整个乳房体积恒定）进行比较，以获得每个组织体素的附加校正值。为了测试准确性，我们将该技术应用于乳房切除标本的锥束 CT 图像。校正后，图像显示前视图和侧视图切片的信号均匀性显着改善。脂肪组织 CT 数量的层内和层间变化的减少支持了我们的观察。 (C) 2007 年美国医学物理学家协会。
In cone beam breast computed tomography (CT), scattered radiation leads to nonuniform biasing of CT numbers known as a cupping artifact. Besides being visual distractions, cupping artifacts appear as background nonuniformities, which impair efficient gray scale windowing and pose a problem in threshold based volume visualization/segmentation. To overcome this problem, we have developed a background nonuniformity correction method specifically designed for cone beam breast CT. With this technique, the cupping artifact is modeled as an additive background signal profile in the reconstructed breast images. Due to the largely circularly symmetric shape of a typical breast, the additive background signal profile was also assumed to be circularly symmetric. The radial variation of the background signals was estimated by measuring the spatial variation of adipose tissue signals in front view breast images. To extract adipose tissue signals in an automated manner, a signal sampling scheme in polar coordinates and a background trend fitting algorithm were implemented. The background fits compared with targeted adipose tissue signal value (constant throughout the breast volume) to get an additive correction value for each tissue voxel. To test the accuracy, we applied the technique to cone beam CT images of mastectomy specimens. After correction, the images demonstrated significantly improved signal uniformity in both front and side view slices. The reduction of both intraslice and interslice variations in adipose tissue CT numbers supported our observations. (C) 2007 American Association of Physicists in Medicine.