Clinic for Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany.
Department of Neuroradiology, University Hospital Heidelberg, Heidelberg, Germany.
PLoS One. 2020 Feb 10;15(2):e0228578. doi: 10.1371/journal.pone.0228578. eCollection 2020.
To compare image quality and metal artifact reduction between virtual monochromatic spectral imaging (VMSI), linearly blended dual-energy (DE) and single-energy (SE) images, each with and without dedicated iterative metal artifact reduction (iMAR) for CT-guided biopsy.
A biopsy trocar was positioned in the liver of six pigs. DE (Sn140/100kVp) and SE (120kVp/200mAs) acquisitions were performed with equivalent dose. From dual-energy datasets DE Q30-3 images and VMSI between 40-180 keV in steps of 20 keV were generated. From SE datasets I30-3 images were reconstructed. All images were reconstructed with and without iMAR. Objective image quality was analyzed applying density measurements at standardized positions (e.g. trocar tip and liver parenchyma adjacent to the trocar tip) and semi-automated threshold based segmentation. Subjective image quality was performed using semi-quantitative scores. Analyses were performed by two observers.
At the trocar tip quantitative image analysis revealed significant difference in CT numbers between reconstructions with iMAR compared to reconstructions without iMAR for VMSI at lower keV levels (80 and 100 keV; p = 0.03) and DE (p = 0.03). For liver parenchyma CT numbers were significantly higher in VMSI at high keV compared to low keV (p≤0.01). VMSI at high keV also showed higher CT numbers compared to DE and SE images, though not the level of statistical significance. The best signal-to-noise ratio for VMSI was at 80 keV and comparable to DE and SE. Noise was lowest at 80 keV and lower than in DE and SE. Subjective image quality was best with VMSI at 80 keV regardless of the application of iMAR. iMAR significantly improved image quality at levels of 140 keV and 160 keV. Interreader-agreement was good for quantitative and qualitative analysis.
iMAR improved image quality in all settings. VMSI with iMAR provided metal artifact reduction and better image quality at 80 keV and thus could improve the accurate positioning in CT-guided needle biopsy. In comparison, DE imaging did not improve image quality compared to SE.
比较虚拟单能量光谱成像（VMSI）、线性能量融合双能（DE）和单能（SE）图像在 CT 引导下活检中的图像质量和金属伪影减少效果，分别在有和没有专用迭代金属伪影减少（iMAR）的情况下。
将活检穿刺针放置在 6 头猪的肝脏中。使用等效剂量进行 DE（Sn140/100kVp）和 SE（120kVp/200mAs）采集。从双能数据集生成 DE Q30-3 图像和 VMSI 在 40-180keV 之间以 20keV 的步长。从 SE 数据集重建 I30-3 图像。所有图像均在有和没有 iMAR 的情况下进行重建。应用标准化位置（例如穿刺针尖端和穿刺针尖端附近的肝实质）的密度测量和半自动基于阈值的分割进行客观图像质量分析。使用半定量评分进行主观图像质量评估。由两名观察者进行分析。
在穿刺针尖端，定量图像分析显示，在较低 keV 水平（80keV 和 100keV；p = 0.03）和 DE（p = 0.03）下，有 iMAR 的重建与没有 iMAR 的重建相比，VMSI 的 CT 值存在显著差异。对于肝实质，在高 keV 下的 VMSI 的 CT 值明显高于低 keV（p≤0.01）。与 DE 和 SE 图像相比，VMSI 在高 keV 下也显示出更高的 CT 值，尽管没有达到统计学意义的水平。VMSI 的最佳信噪比在 80keV，与 DE 和 SE 相当。噪声在 80keV 时最低，低于 DE 和 SE。无论是否应用 iMAR，VMSI 在 80keV 时的主观图像质量最佳。iMAR 显著改善了 140keV 和 160keV 水平的图像质量。定量和定性分析的读者间一致性良好。
iMAR 改善了所有情况下的图像质量。有 iMAR 的 VMSI 可减少金属伪影并在 80keV 时提供更好的图像质量，因此可以提高 CT 引导下针活检的准确定位。相比之下，DE 成像与 SE 相比并未改善图像质量。
