Department of Radiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China; Department of Radiology, The Sixth People's Hospital of Chengdu, Chengdu, Sichuan, China.
Department of Radiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China.
Eur J Radiol. 2022 May;150:110246. doi: 10.1016/j.ejrad.2022.110246. Epub 2022 Mar 10.
To investigate the feasibility of contrast agent and injection rate reduction for dual-layer spectral detector computed tomography (SDCT) imaging of the superior mesenteric artery (SMA) using virtual monochromatic image (VMI).
A total of 102 patients who underwent abdominal arterial phase-enhanced SDCT examination due to suspected abdominal diseases were prospectively selected and divided into control group, low concentration/dose groups (groups 370-0.7, 300-1.0, and 300-0.9) and low injection rate groups (groups 2-370 and 2-350). Compared with the control group, low concentration/dose groups and low injection rate groups lowered the concentration/dose or injection rate of the contrast agent to varying degrees. The raw data obtained in each group were reconstructed using hybrid-iterative reconstruction and projection spatial-spectral reconstruction algorithm. The image quality of the SMA in conventional images (CI) and in VMIs (interval: 10 keV) during the arterial phase was analyzed. Multiplanar reformation images and volume rendering images of the SMA were reconstructed. Image quality objective evaluation indexes included the CT values, contrast-to-noise ratio, signal-to-noise ratio, and diameter of the SMA. The diameter of the SMA was determined by the CT values profile curve and its full width at half maximum. Two doctors independently evaluated the subjective image quality of multiplanar reformation coronal images and volume rendering images according to a 5-point scale. Repeated analysis of variance and Friedman test were used to compare the differences in the objective evaluation indexes and subjective scores between VMIs and CI in the same group. The Dunnett's t-test or Dunnett's T3 test and Kruskal-Wallis H-test were used to compare the differences in the objective evaluation indexes and subjective scores between the experimental and control groups.
VMIs of the SMA in each group had the best image quality at 60 keV, and VMI in each group were better than their respective CI to varying degrees. Although the objective (CT values, contrast-to-noise ratio, and signal-to-noise ratio) and subjective (subjective scores) indexes of CI in the low concentration/dose groups and low injection rate groups were lower than those of CI in the control group to varying degrees, these indexes of VMI in the low concentration/dose groups and group 2-370 were equal to or even better than the CI in the control group.
VMI using SDCT could effectively reduce the contrast agent load while providing equivalent or better SMA image quality compared with CI obtained using a conventional contrast agent protocol. When the injection rate was lowered to 2.0 ml/s for a high-concentration contrast agent (370 mgI/ml), the SMA image quality at VMI was comparable with that of the CI in the control group.
使用虚拟单能量图像（VMI）研究双能量光谱探测器 CT（SDCT）对肠系膜上动脉（SMA）进行动脉期增强扫描时，降低对比剂浓度/剂量和注射速率的可行性。
前瞻性选择 102 例因怀疑腹部疾病而行腹部动脉期增强 SDCT 检查的患者，分为对照组、低浓度/剂量组（370-0.7、300-1.0 和 300-0.9 组）和低注射速率组（2-370 和 2-350 组）。与对照组相比，低浓度/剂量组和低注射速率组降低了对比剂的浓度/剂量或注射速率。使用混合迭代重建和投影空间频谱重建算法对每组的原始数据进行重建。分析动脉期常规图像（CI）和 VMI（间隔：10 keV）中 SMA 的图像质量。重建 SMA 的多平面重建图像和容积再现图像。图像质量客观评价指标包括 SMA 的 CT 值、对比噪声比、信噪比和直径。通过 CT 值轮廓曲线及其半最大值全宽确定 SMA 的直径。两位医生根据 5 分制独立评价冠状位多平面重建图像和容积再现图像的主观图像质量。采用重复方差分析和 Friedman 检验比较同一组内 VMI 和 CI 的客观评价指标和主观评分的差异。采用 Dunnett's t 检验或 Dunnett's T3 检验和 Kruskal-Wallis H 检验比较实验组和对照组之间的客观评价指标和主观评分的差异。
每组 SMA 的 VMI 在 60 keV 时具有最佳的图像质量，且 VMI 在不同程度上优于各自的 CI。尽管低浓度/剂量组和低注射速率组的 CI 的客观（CT 值、对比噪声比和信噪比）和主观（主观评分）指标在不同程度上低于对照组的 CI，但低浓度/剂量组和 2-370 组的 VMI 这些指标与对照组的 CI 相当，甚至更好。
与使用常规造影剂方案获得的 CI 相比，SDCT 的 VMI 可有效降低对比剂负荷，同时提供等效或更好的 SMA 图像质量。当以 2.0 ml/s 的注射速率使用高浓度造影剂（370 mgI/ml）时，VMI 的 SMA 图像质量与对照组的 CI 相当。
