From the Department of Diagnostic and Interventional Radiology, University Hospital Augsburg, Augsburg.
Invest Radiol. 2023 Sep 1;58(9):691-696. doi: 10.1097/RLI.0000000000000967.
The aim of this study was to compare the effectiveness of common strategies for artifact reduction of dental material in photon-counting detector computed tomography data sets.
Patients with dental material who underwent clinically indicated CT of the neck were enrolled. Image series were reconstructed using a standard and sharp kernel, with and without iterative metal artifact reduction (IMAR) (Qr40, Qr40 IMAR , Qr60, Qr60 IMAR ) at different virtual monoenergetic imaging (VMI) levels (40-190 keV). On representative slice positions with and without dental artifacts, mean and standard deviation of CT values were measured in all series at identical locations. The mean absolute error of CT values ( ) and the artifact index (AIX) were calculated and analyzed focusing on 3 main comparisons: ( a ) different VMI levels versus 70 keV, ( b ) standard versus sharp kernel, and ( c ) nonuse or use of IMAR reconstruction. The Wilcoxon test was used to assess differences for nonparametric data.
The final cohort comprised 50 patients. Artifact measures decreased for VMI levels >70 keV, yet only significantly so for reconstructions using IMAR (maximum reduction, 25%). The higher image noise of the sharp versus standard kernel is reflected in higher AIX values and is more pronounced in IMAR series (maximum increase, 38%). The most profound artifact reduction was observed for IMAR reconstructions (maximum reduction : 84%; AIX: 90%).
Metal artifacts caused by large amounts of dental material can be substantially reduced by IMAR, regardless of kernel choice or VMI settings. Increasing the keV level of VMI series, on the other hand, only slightly reduces dental artifacts; this effect, however, is additive to the benefit conferred by IMAR reconstructions.
本研究旨在比较光子计数探测器 CT 数据集减少牙科材料伪影的常用策略的有效性。
纳入因临床需要行颈部 CT 检查且体内含有牙科材料的患者。采用标准和锐利核，分别在不同虚拟单能量成像（VMI）水平（40-190keV），以及是否使用迭代金属伪影降低（IMAR）（Qr40、Qr40IMAR、Qr60、Qr60IMAR）重建图像序列。在有和没有牙科伪影的代表性层面位置，在所有系列中，在相同位置测量所有 CT 值的均值和标准差。重点关注 3 个主要比较，计算和分析 CT 值的平均绝对误差（ ）和伪影指数（AIX）：（a）不同 VMI 水平与 70keV 相比，（b）标准核与锐利核相比，（c）不使用或使用 IMAR 重建。对于非参数数据，使用 Wilcoxon 检验评估差异。
最终纳入 50 例患者。VMI 水平>70keV 时，伪影测量值降低，但仅在使用 IMAR 重建时显著降低（最大降幅 25%）。锐利核与标准核相比，图像噪声更高，这反映在更高的 AIX 值中，且在使用 IMAR 系列时更明显（最大增幅 38%）。观察到 IMAR 重建时伪影降低最明显（最大降幅：84%；AIX：90%）。
无论选择核或 VMI 设置，大量牙科材料引起的金属伪影均可通过 IMAR 显著降低。另一方面，增加 VMI 系列的 keV 水平仅能略微降低牙科伪影；然而，这种效果是对 IMAR 重建带来的益处的补充。
