Optimized low-kV spectrum of dual-energy CT equipped with high-kV tin filtration for electron density measurements Med
Optimized low-kV spectrum of dual-energy CT equipped with high-kV tin filtration for electron density measurements Med
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配备高 kV 锡过滤的双能 CT 的优化低 kV 谱，用于电子密度测量 Med
DOI：
10.1118/1.3584200
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Masatoshi Saito
中科院分区：
文献类型：
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作者：
Y.Takada;T.Nihei;他3名;無藤隆;Masatoshi Saito
目的介绍了双能CT （DECT）的低千伏谱优化方法，该方法可用于定量获取电子密度信息，这对放疗治疗计划至关重要。此外，还初步进行了解析DECT图像模拟，以证明优化后的DECT在减少光束硬化方面的有效性。方法为了优化DECT的低千伏谱，作者计算了直径为50 cm的圆柱形水影的波束硬化误差、CT剂量指数和管载荷，并对不同的过滤材料组合、厚度范围和低千伏管电位进行了计算。此外，采用0.4 mm锡（Sn）滤波的140 kV单管电位用于高kV扫描，这与第二代双源CT扫描仪的商业实现类似。然后，将优化后的光谱参数应用于具有16个体状组织插入的虚拟固体水幻影的二维扇形光束几何结构的解析DECT图像模拟。结果作者预测，在90 kV时，最佳的低kV滤波为0.144 mm钨(W)，因为它在较低的管负载和剂量下产生最小的波束硬化误差。使用W过滤获得的高kV管负载和剂量分别为99 ma和2.2 mGy。这些值几乎等于2.5 mm Al在100 kV （100 ma和2.3 mGy）的情况下获得的值，在本研究中被视为参考过滤；然而，W过滤显著降低了光束硬化误差，从9.5%降至1.4%。相应的低千伏管负载（112 mAs）比参考情况（21 mAs）大5倍，但由于低千伏管负载与参考情况（100 mAs）的高千伏管负载相当，因此保持在一定的实际水平。模拟图像反映了束硬化减容的优越性；例如，通过使用W滤波器，即使没有进行束硬化校正，与参考滤波相比，模拟和理论的皮质骨电子密度值之间的束硬化诱导偏差也从7.4降低到1.2%。结论在束流硬化降低方面，低kV W过滤的DECT在实际管载限制下，在不增加剂量的情况下，更能有效地定量测量电子密度。
PurposeThis paper describes the low‐kV spectral optimization of dual‐energy CT (DECT) equipped with high‐kV tin filtration for the quantitative acquisition of electron density information, which is essential for treatment planning in radiotherapy. In addition, an analytical DECT image simulation was preliminarily performed to demonstrate the effectiveness of the optimized DECT with respect to the beam‐hardening reduction.MethodsTo optimize the low‐kV spectrum of DECT, the author calculated the beam‐hardening error, CT dose index, and tube loadings for a 50‐cm diameter cylindrical water phantom with various combinations of filter materials, a range of thicknesses, and low‐kV tube potentials. In addition, a single tube potential of 140 kV filtered by 0.4 mm tin (Sn) was employed for high‐kV scanning, as is similar to the commercial implementation of the second‐generation dual‐source CT scanner. The optimized spectral parameters were then applied to the analytical DECT image simulation using two‐dimensional fan‐beam geometry for a virtual solid water phantom with 16 bodylike tissue inserts.ResultsThe author predicts that an optimal low‐kV filtration would be 0.144‐mm tungsten (W) at 90 kV, as it yields a minimal beam‐hardening error with lower tube loadings and dose. The high‐kV tube loading and dose obtained using the W filtration were 99 mAs and 2.2 mGy, respectively. These values are nearly equal to those obtained in the case of 2.5 mm Al at 100 kV (100 mAs and 2.3 mGy), which was regarded in this study as a reference filtration; however, the W filtration significantly reduced the beam‐hardening error, from 9.5 to 1.4%. The corresponding low‐kV tube loading (112 mAs) was five times greater than that of the reference case (21 mAs), but it was maintained at a certain practical level since the low‐kV tube loading was comparable to the high‐kV tube loading of the reference (100 mAs). The superiority of the beam‐hardening reduction is reflected in the simulated images; for example, by the use of the W filter, the beam‐hardening‐induced deviation between the simulated and theoretical electron density values of cortical bone was reduced from 7.4 to 1.2% as compared with the reference filtration, even though no correction for beam hardening was performed.ConclusionsIn terms of beam hardening reduction, the DECT with the low‐kV W filtration is more effective for the quantitative measurement of electron density within a practical limit of tube loadings and without additional dose.