Universal orbit design for metal artifact elimination.
Universal orbit design for metal artifact elimination.
复制标题
用于消除金属工件的通用轨道设计。
DOI：
10.1088/1361-6560/ac6aa0
复制
发表时间：
2022
影响因子：
3.5
通讯作者：
Stayman,JWebster
中科院分区：
文献类型：
--
作者：
Gang,GraceJ;Stayman,JWebster
目的金属伪影是CT和锥束CT的一个长期存在的问题。在这项工作中，我们建议通过使用非圆形轨道提供更好的数据采样来减少甚至消除金属伪影。方法：我们将任何与金属相交的测量数据视为缺失数据，并旨在设计一个通用轨道，该轨道通常可以容纳任意金属形状和位置。我们采用了基于Tuy条件的局部采样完整性度量来量化存在金属的采样程度。轨道设计采用了所有可能金属位置的最大最小目标。一类简单的正弦轨道被评价为频率、最大倾斜角和轨道范围的函数。在成像台上进行这些轨道的实验实施，并在两个模型上进行评估，一个包含金属球，另一个包含用于脊柱固定的椎弓根螺钉组件。比较了三种方法的金属伪影减少（MAR）性能：仅非圆轨道，仅算法校正和组合方法。主要结果客观天体的理论评价倾向于大倾角和大轨道范围的正弦轨道。此外，利用冗余方位角采样非冗余数据的轨道具有更好的性能，例如360度采集的偶数或非整数频率正弦波。实验数据支持理论评估中观察到的趋势。使用偶数或非整数频率轨道进行重建，即使存在多个金属物体，甚至在没有MAR算法的情况下，也能以更精细的分辨率呈现更少的条纹伪影和背景细节。非圆轨道与MAR算法相结合的方法获得了最好的性能。观察到的图像质量趋势得到了采样和条纹伪影严重程度的定量测量的支持。这项工作表明，正弦轨道通常对金属伪影具有鲁棒性，可以为提高介入成像的图像质量提供途径。
ObjectiveMetal artifacts are a persistent problem in CT and cone-beam CT. In this work, we propose to reduce or even eliminate metal artifacts by providing better sampling of data using non-circular orbits.ApproachWe treat any measurements intersecting metal as missing data, and aim to design a universal orbit that can generally accommodate arbitrary metal shapes and locations. We adapted a local sampling completeness metric based on Tuy's condition to quantify the extent of sampling in the presence of metal. A maxi-min objective over all possible metal locations was used for orbit design. A simple class of sinusoidal orbits was evaluated as a function of frequencies, maximum tilt angles, and orbital extents. Experimental implementation of these orbits were performed on an imaging bench and evaluated on two phantoms, one containing metal balls and the other containing a pedicle screw assembly for spine fixation. Metal artifact reduction (MAR) performance was compared amongst three approaches: non-circular orbits only, algorithmic correction only, and a combined approach.Main resultsTheoretical evaluations of the objective favor sinusoidal orbits with large tilt angles and large orbital extents. Furthermore, orbits that leverage redundant azimuthal angles to sample non-redundant data have better performance, eg even or non-integer frequency sinusoids for a 360 acquisition. Experimental data support the trends observed in theoretical evaluations. Reconstructions using even or non-integer frequency orbits present less streaking artifacts and background details with finer resolution, even when multiple metal objects are present and even in the absence of MAR algorithms. The combined approach of non-circular orbits and MAR algorithm yields the best performance. The observed trend in image quality is supported by quantitative measures of sampling and severity of streaking artifact.SignificanceThis work demonstrates that sinusoidal orbits are generally robust against metal artifacts and can provide an avenue for improved image quality in interventional imaging.