ISSN 1004-4140
CN 11-3017/P
王诗耕, 浦仁旺, 刘义军, 等. 能谱CT下肢静脉成像优化:模体研究[J]. CT理论与应用研究(中英文), xxxx, x(x): 1-10. DOI: 10.15953/j.ctta.2024.117.
引用本文: 王诗耕, 浦仁旺, 刘义军, 等. 能谱CT下肢静脉成像优化:模体研究[J]. CT理论与应用研究(中英文), xxxx, x(x): 1-10. DOI: 10.15953/j.ctta.2024.117.
WANG S G, PU R W, LIU Y J, et al. Optimization of Dual-Energy Spectral Lower-Extremity CT Venography Scanning Protocol: Phantom Study[J]. CT Theory and Applications, xxxx, x(x): 1-10. DOI: 10.15953/j.ctta.2024.117. (in Chinese).
Citation: WANG S G, PU R W, LIU Y J, et al. Optimization of Dual-Energy Spectral Lower-Extremity CT Venography Scanning Protocol: Phantom Study[J]. CT Theory and Applications, xxxx, x(x): 1-10. DOI: 10.15953/j.ctta.2024.117. (in Chinese).

能谱CT下肢静脉成像优化:模体研究

Optimization of Dual-Energy Spectral Lower-Extremity CT Venography Scanning Protocol: Phantom Study

  • 摘要: 目的:基于模体研究优化能谱下肢CT静脉成像(CTV)方案。方法:在能量CT质控模体的内部孔洞中放置测试插件以模拟临床场景。使用4 mgI/mL碘棒模拟下肢静脉增强;将大小不同的鸭血块放入4 mgI/ml的碘溶液试管中,模拟下肢静脉内的大小血栓。采用Revolution CT对置入碘棒和试管的模体进行CT常规成像(A组)和能谱成像(B组)。A组成像参数:管电压120 kVp,管电流自动调节技术(100~600 mA),噪声指数(NI)为10,采用后置40%的多模型自适应统计迭代重建算法(ASIR-V)进行图像重建;B组成像参数:能谱成像(GSI)模式,管电压80/140 kVp瞬切,管电流采用GSI Assist技术,并根据NI=10、11、12设置3个扫描组。在每个扫描组中重建40~70 keV间隔10 keV的单能量图像,每个单能量图像分别结合后置40%、60%、80% ASIR-V进行图像重建,共得到36组图像。A、B组其他成像参数均一致。扫描完成后记录A、B组有效辐射剂量(ED),计算两组碘棒对比噪声比(CNR),评估两组主观图像质量以及识别血栓的真阳性率和假阳性率。结果:B组NI设置为11和12的ED分别比A组低21.5%和32.2%。B组NI为10和11的扫描组中,除了70 keV结合40% ASIR-V和60 keV结合40% ASIR-V的图像外,其余图像的碘棒CNR均高于A组。B组碘棒边缘锐利度得分最高的组别是NI为10的扫描组中,50 keV结合40%、60% ASIR-V的图像,以及NI为11的扫描组中,50 keV结合60% ASIR-V的图像,这3组图像得分均为5(4,5)且优于A组得分3(3,4)。A组图像识别大血栓的真阳性率和假阳性率分别为65.0%和30.0%;识别小血栓的真阳性率和假阳性率分别为55.0%和50.0%。B组NI为10和11的扫描组中,50 keV结合60% ASIR-V图像识别血栓的效能最佳并优于A组,其中识别大血栓的真阳性率和假阳性率分别为90.0%和5.0%,识别小血栓的真阳性率和假阳性率分别为80.0%和5.0%。结论:将NI设置为11,并重建50 keV结合60% ASIR-V的单能量图像是能谱下肢CTV的最佳成像方案,可在模体研究中实现图像质量与辐射剂量之间的平衡。

     

    Abstract:
    Objective To optimize a scanning protocol for dual-energy spectral lower-extremity computed tomography (CT) venography (CTV) based on a phantom study.
    Methods Test plugs were placed in the cavities of an energy CT quality-control phantom to simulate clinical scenarios. A 4 mgI/mL iodine rod was used to mimic venous enhancement in the lower extremities, and duck blood clots of various sizes were placed in test tubes containing 4 mgI/mL of iodine solution to simulate thrombi of different sizes in the lower-extremity veins. Revolution CT was used to perform standard CT imaging (Group A) and spectral imaging (Group B) on phantoms containing iodine rods and test tubes. The imaging parameters for Group A were as follows: tube voltage of 120 kVp, auto tube-current technology (100–600 mA), noise index (NI) of 10, and image reconstruction using 40% posterior multimodel adaptive statistical iterative reconstruction (ASIR-V). The imaging parameters for Group B were spectral imaging (GSI) mode, instantaneous dual tube voltage of 80/140 kVp, tube current with GSI Assist technology, and three scan groups based on NI values of 10, 11, and 12. For each scan group, monoenergetic images at 40–70 keV with 10 keV intervals were reconstructed, each combined with 40%, 60%, and 80% posterior ASIR-V, which resulted in 36 image sets. Other imaging parameters for Groups A and B were consistent. The effective radiation doses (ED) for Groups A and B were recorded after scanning, and the contrast-to-noise ratio (CNR) of the iodine rods was calculated. Subjective image quality and true- and false-positive rates for thrombus identification were assessed.
    Results The EDs for Group B, with NI values of 11 and 12, were 21.5% and 32.2% lower than those for Group A, respectively. In Group B, for the scan groups with NI values of 10 and 11, except for the images at 70 keV combined with 40% ASIR-V and at 60 keV combined with 40% ASIR-V, the CNR of the iodine rods was higher than that in Group A. The highest edge-sharpness scores for the iodine rods in Group B were observed in the scan group with an NI value of 10 for images at 50 keV combined with 40% and 60% ASIR-V, and in the scan group with an NI value of 11 for images at 50 keV combined with 60% ASIR-V. These three image sets scored 5 (4, 5) compared with Group A’s score of 3 (3, 4). The true- and false-positive rates for large-thrombus identification in Group A were 65.0% and 30.0%, respectively, whereas those for small-thrombus identification were 55.0% and 50.0%, respectively. In Group B, the best thrombus-identification efficacy was observed in the scan groups, with NI values of 10 and 11 for images at 50 keV combined with 60% ASIR-V. The true- and false-positive rates for large-thrombus identification were 90.0% and 5.0%, respectively, whereas those for small-thrombus identification were 80.0% and 5.0%, respectively.
    Conclusions Setting the NI to 11 and reconstructing monoenergetic images at 50 keV combined with 60% ASIR-V is the optimal imaging strategy for dual-energy spectral lower-extremity CTV, which balances between image quality and radiation dose in the current phantom study.

     

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