Crescent artifacts in cone-beam CT
Crescent artifacts in cone-beam CT
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DOI：
10.1118/1.3567508
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发表时间：
2011-04-01
期刊：
影响因子：
3.8
通讯作者：
Yin, Fang-Fang
中科院分区：
文献类型：
--
作者：
Giles, William;Bowsher, James;Yin, Fang-Fang
目的：在图像引导放射治疗中，锥形束CT已被用于治疗室中的三维靶定位。在许多这些锥形束CT图像中，可以看到暗新月形伪影和亮新月形伪影。本研究探讨这种伪影的潜在原因和技术，以减轻crescents.Methods：三个偏差从一个理想的几何形状进行了模拟，以评估他们的能力，造成月牙伪影：蝴蝶结过滤器下垂，X射线管下垂，和X射线管旋转。通过将模拟投影中的偏移与临床系统中观察到的偏移相匹配，估计这些偏差的幅度。为了校正伪影，采集角度相关的空白投影并将其纳入图像重建。使用不同数量（1-380）的空白投影评价伪影减少程度。扫描仪获得的幻影和病人的研究进行了证明所提出的校正method.Results的有效性：所有三个调查的原因新月形伪影介绍了类似的错误建模的收购的投影和类似的新月形伪影。这些伪影所需的偏差范围为0.5-5 mm或0.1 mm。在200 °扫描角范围内，对于1-380个空白投影，RMS误差从8.91 x 10（-4）减小到5.25 x 10（-7）。在病人和幻影的研究中，重建，利用380空白的预测在很大程度上减轻了新月artifaction.Conclusions：从一个理想的几何形状的小偏差，可能会导致新月形的文物，由于在领结过滤器陡峭的梯度。角度相关的空白投影可以在很大程度上减轻伪影。(C)2011年美国医学物理学家协会。[DOI 10.1118/1.3567508]
Purpose: In image-guided radiation therapy, cone-beam CT has been adopted for three-dimensional target localization in the treatment room. In many of these cone-beam CT images, dark and light crescent artifacts can be seen. This study investigates potential causes of this artifact and a technique for mitigating the crescents.Methods: Three deviations from an ideal geometry were simulated to assess their ability to cause crescent artifacts: Bowtie filter sag, x-ray tube sag, and x-ray tube rotation. The magnitudes of these deviations were estimated by matching shifts in simulated projections to those observed with clinical systems. To correct the artifacts, angle-dependent blank projections were acquired and incorporated into image reconstruction. The degree of artifact reduction was evaluated with varying numbers (1-380) of blank projections. Scanner-acquired phantom and patient studies were conducted to demonstrate the effectiveness of the proposed correction method.Results: All three investigated causes of the crescent artifact introduced similar mismodeling of the acquired projections and similar crescent artifacts. The deviations required for these artifacts were in the range of 0.5-5 mm or 0.1. RMS error is reduced from 8.91 x 10(-4) to 5.25 x 10(-7) for 1-380 blank projections over a 200 scan angle. In the patient and phantom studies, reconstructions that utilized 380 blank projections largely mitigated the crescent artifacts.Conclusions: Small deviations from an ideal geometry can result in crescent artifacts due to steep gradients in the bowtie filter. Angle-dependent blank projections can largely alleviate the artifacts. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3567508]