Division of Neuroradiology, Department of Imaging and Medical Information Sciences, Geneva University Hospitals, Rue Gabrielle-Perret-Gentil 4, 1205, Geneva, Switzerland.
Division of Radiology, Department of Imaging and Medical Information Sciences, Geneva University Hospitals, Rue Gabrielle-Perret-Gentil 4, 1205, Geneva, Switzerland.
Clin Neuroradiol. 2019 Dec;29(4):741-749. doi: 10.1007/s00062-018-0701-5. Epub 2018 Jun 19.
To investigate the impact of iterative metal artifact reduction (iMAR) on artifacts related to neurosurgical clips or endovascular coils when combined to filtered back projection (FBP) or advanced modelled iterative reconstruction (ADMIRE).
In this study 21 unenhanced brain computed tomography (CT) examinations were reconstructed with FBP and level 2 of ADMIRE, both techniques with and without iMAR algorithm, resulting in 4 series per acquisition. Subjective assessment of artifact reduction was performed as a double-blinded evaluation with a 5-point-scale. Objective analysis was performed by comparing central tendencies and distributions of voxel densities. The central tendency was assessed as the mean voxel density in Hounsfield units. The distribution was assessed by evaluating the shape and asymmetry of the histograms of voxels densities with measures of kurtosis and skewness, respectively.
Inter-reader agreement was excellent (>0.8). FBP and ADMIRE without iMAR were scored 4 and with iMAR 5. Unusual artifacts were noted in all of the series reconstructed with iMAR, especially when combined with ADMIRE. Kurtosis revealed statistical differences for all reconstruction techniques (p ≤ 0.0007) except for the association of FBP with iMAR (p = 0.2211) for the coiling population and skewness demonstrated no statistical difference in any population (p ≥ 0.0558), confirming the subjective analysis results, except for the ADMIRE algorithm with or without iMAR (p ≤ 0.0342) in the coiling population.
iMAR led to the reduction in artifacts due to intracranial metallic devices. However, it created a new artifact in the form of a halo of photon-starvation, especially when combined with ADMIRE. The combination of FBP and iMAR seems more suitable, combining the beneficial metal artifact reduction without the emergence of a halo of photon starvation just around the point of interest.
研究迭代金属伪影降低（iMAR）技术结合滤波反投影（FBP）或高级模型迭代重建（ADMIRE）对神经外科夹或血管内线圈相关伪影的影响。
本研究对 21 例未经增强的脑 CT 扫描进行了 FBP 和 ADMIRE 级别 2 的重建，均采用和不采用 iMAR 算法，每次采集得到 4 个序列。采用 5 分制进行盲法评估，对伪影减少程度进行主观评估。通过比较体素密度的中心趋势和分布进行客观分析。中心趋势采用 CT 值的平均体素密度评估。分布采用评估体素密度直方图的形状和不对称性，分别用峰度和偏度进行评估。
读者间的一致性极好（>0.8）。未采用 iMAR 的 FBP 和 ADMIRE 评分为 4 分，而采用 iMAR 的评分为 5 分。在所有采用 iMAR 重建的序列中都观察到了异常伪影，尤其是与 ADMIRE 联合应用时。除了 FBP 与 iMAR 的联合应用（p = 0.2211）之外，所有重建技术的峰度均存在统计学差异（p ≤ 0.0007），而偏度在任何人群中均无统计学差异（p ≥ 0.0558），证实了主观分析结果，除了在血管内线圈人群中 ADMIRE 算法与 iMAR 的联合应用（p ≤ 0.0342）之外。
iMAR 可减少颅内金属装置引起的伪影。然而，它会产生一种新的伪影，即光子饥饿晕，尤其是与 ADMIRE 联合应用时。FBP 和 iMAR 的联合应用似乎更合适，它结合了有益的金属伪影减少，而不会在感兴趣区域周围出现光子饥饿晕。
