A simple, direct method for X-ray scatter estimation and correction in digital radiography and cone-beam CT
A simple, direct method for X-ray scatter estimation and correction in digital radiography and cone-beam CT
复制标题
DOI：
10.1118/1.2148916
复制
发表时间：
2006-01-01
期刊：
影响因子：
3.8
通讯作者：
Jaffray, DA
中科院分区：
文献类型：
--
作者：
Siewerdsen, JH;Daly, MJ;Jaffray, DA
X 射线散射对锥束 CT (CBCT) 的图像质量造成重大限制，导致对比度降低、图像伪影和 CT 数字精度缺乏。我们报告了一种简单的散射校正方法的性能，其中在每个投影中根据准直器叶片后面的探测器边缘附近的像素值直接估计散射注量。该算法基于以下简单假设进行操作：准直器阴影中的信号可归因于 X 射线散射，并且通过在沿着准直器叶片后面的探测器的顶部和底部边缘测量的像素值之间进行插值来估计 2D 散射注量。从每个投影中减去所得的散射注量估计，以生成用于 CBCT 重建的仅主要图像的估计。在 CBCT 实验台上的体模实验中研究了性能，并在 CBCT 引导放射治疗的临床前系统上获得的患者图像（头部、腹部和骨盆部位）中证明了对图像质量的影响。该算法可显着减少散射伪影，且不会影响对比度噪声比 (CNR)。例如，在头部模型中，拔罐伪影基本上被消除，CT数字精度恢复到3%以内，CNR（乳房到水）提高了高达50%。同样，在人体模型中，拔罐伪影至少减少了 2 倍，且 CNR 没有损失。患者图像的均匀性、准确性和对比度显着提高，所有研究部位的图像质量均得到全面改善。定性评估表明，在散射校正重建中可以清楚地描绘出原本无法检测到的软组织结构。由于在每个投影中直接估计散射，因此该算法在系统几何形状、患者体型和异质性、患者运动等方面具有稳健性。无需先验信息、分析建模或蒙特卡罗即可操作，该技术很容易作为 CBCT 重建中的预处理步骤纳入，以显着减少散射。 (c) 2006 年美国医学物理学家协会。
X-ray scatter poses a significant limitation to image quality in cone-beam CT (CBCT), resulting in contrast reduction, image artifacts, and lack of CT number accuracy. We report the performance of a simple scatter correction method in which scatter fluence is estimated directly in each projection from pixel values near the edge of the detector behind the collimator leaves. The algorithm operates on the simple assumption that signal in the collimator shadow is attributable to x-ray scatter, and the 2D scatter fluence is estimated by interpolating between pixel values measured along the top and bottom edges of the detector behind the collimator leaves. The resulting scatter fluence estimate is subtracted from each projection to yield an estimate of the primary-only images for CBCT reconstruction. Performance was investigated in phantom\ experiments on an experimental CBCT benchtop, and the effect on image quality was demonstrated in patient images (head, abdomen, and pelvis sites) obtained on a preclinical system for CBCT-guided radiation therapy. The algorithm provides significant reduction in scatter artifacts without compromise in contrast-to-noise ratio (CNR). For example, in a head phantom, cupping artifact was essentially eliminated, CT number accuracy was restored to within 3%, and CNR (breast-to-water) was improved by up to 50%. Similarly in a body phantom, cupping artifact was reduced by at least a factor of 2 without loss in CNR. Patient images demonstrate significantly increased uniformity, accuracy, and contrast, with an overall improvement in image quality in all sites investigated. Qualitative evaluation illustrates that soft-tissue structures that are otherwise undetectable are clearly delineated in scatter-corrected reconstructions. Since scatter is estimated directly in each projection, the algorithm is robust with respect to system geometry, patient size and heterogeneity, patient motion, etc. Operating without prior information, analytical modeling, or Monte Carlo, the technique is easily incorporated as a preprocessing step in CBCT reconstruction to provide significant scatter reduction. (c) 2006 American Association of Physicists in Medicine.