Abstract：
OBJECTIVE: Coronary artery calcium scoring (CACs) at 120 kVp is the standard practice. It is an important tool for preventative management of asymptomatic patients. However, the current dose delivery, albeit patient-size dependent, does not connect the CACs specific noise requirement to the dose, causing significant dose variations. We propose a new approach for optimal dose determination by incorporating the patient-size dependent noise threshold.
METHODS: A polyethylene-based Mercury phantom of various diameters was scanned with a dual-source CT using CACs gating at different volume CT dose index (CTDIvol). The relationship of noise to the diameter and CTDIvol was obtained. The phantom diameter was then converted to the patient chest diameter through a retrospective analysis of a clinical cohort (N = 140). Finally, the patient-size dependent noise threshold was applied, and the optimal dose was derived. The prescribed doses were compared with those from a clinical CACs cohort (N = 262).
RESULTS: A power-exponential relationship was found for the noise versus CTDIvol and phantom diameter (R2 = 0.988). The phantom diameter versus the patient effective diameter was found to obey a linear relationship (R2 = 0.998). Two noise threshold settings were made for dose options: one for more dose saving, and another for tighter noise constraint. Retrospective comparisons with clinical CACs studies showed an average dose reduction of 23% in 80.5% of the cases with option 1. The average dose reduction is 23% in 77.9% of the cases with option 2.
CONCLUSIONS: A new optimal dose scheme dictated by the target noise was established for CACs at 120 kVp. The proposed dose modulation can serve as the baseline from which further dose reduction is possible.
METHODS: A polyethylene-based Mercury phantom of various diameters was scanned with a dual-source CT using CACs gating at different volume CT dose index (CTDIvol). The relationship of noise to the diameter and CTDIvol was obtained. The phantom diameter was then converted to the patient chest diameter through a retrospective analysis of a clinical cohort (N = 140). Finally, the patient-size dependent noise threshold was applied, and the optimal dose was derived. The prescribed doses were compared with those from a clinical CACs cohort (N = 262).
RESULTS: A power-exponential relationship was found for the noise versus CTDIvol and phantom diameter (R2 = 0.988). The phantom diameter versus the patient effective diameter was found to obey a linear relationship (R2 = 0.998). Two noise threshold settings were made for dose options: one for more dose saving, and another for tighter noise constraint. Retrospective comparisons with clinical CACs studies showed an average dose reduction of 23% in 80.5% of the cases with option 1. The average dose reduction is 23% in 77.9% of the cases with option 2.
CONCLUSIONS: A new optimal dose scheme dictated by the target noise was established for CACs at 120 kVp. The proposed dose modulation can serve as the baseline from which further dose reduction is possible.
摘要：
目的：120kVp的冠状动脉钙评分（CACs）是标准方法。它是无症状患者预防性管理的重要工具。然而,当前的剂量输送，尽管取决于患者的大小，不将CAC特定噪音要求连接到剂量，导致显著的剂量变化。我们提出了一种通过合并患者大小相关的噪声阈值来确定最佳剂量的新方法。
方法：使用不同体积CT剂量指数（CTDIvol）的CAC门控，用双源CT扫描各种直径的基于聚乙烯的汞体模。获得了噪声与直径和CTDIvol的关系。然后通过临床队列的回顾性分析将体模直径转换为患者胸部直径(N=140)。最后,应用患者大小相关的噪声阈值，并得出了最佳剂量。将处方剂量与临床CAC队列(N=262)的剂量进行比较。
结果：发现噪声与CTDIvol和体模直径的幂指数关系（R2=0.988）。发现体模直径与患者有效直径服从线性关系(R2=0.998)。对剂量选项进行了两个噪声阈值设置：一个用于更多的剂量节省，和另一个更严格的噪声约束。与临床CAC研究的回顾性比较显示，在选择1的病例中，80.5%的平均剂量减少了23%。在使用选项2的77.9%的病例中,平均剂量减少为23%。
结论：为120kVp的CAC建立了由目标噪声决定的新的最佳剂量方案。所提出的剂量调制可以用作基线,从该基线可以进一步减少剂量。
方法：使用不同体积CT剂量指数（CTDIvol）的CAC门控，用双源CT扫描各种直径的基于聚乙烯的汞体模。获得了噪声与直径和CTDIvol的关系。然后通过临床队列的回顾性分析将体模直径转换为患者胸部直径(N=140)。最后,应用患者大小相关的噪声阈值，并得出了最佳剂量。将处方剂量与临床CAC队列(N=262)的剂量进行比较。
结果：发现噪声与CTDIvol和体模直径的幂指数关系（R2=0.988）。发现体模直径与患者有效直径服从线性关系(R2=0.998)。对剂量选项进行了两个噪声阈值设置：一个用于更多的剂量节省，和另一个更严格的噪声约束。与临床CAC研究的回顾性比较显示，在选择1的病例中，80.5%的平均剂量减少了23%。在使用选项2的77.9%的病例中,平均剂量减少为23%。
结论：为120kVp的CAC建立了由目标噪声决定的新的最佳剂量方案。所提出的剂量调制可以用作基线,从该基线可以进一步减少剂量。
