Evaluation of Stopping Power Ratio Calculation Using Dual-energy Computed Tomography With Fast Kilovoltage Switching for Treatment Planning of Particle Therapy
Evaluation of Stopping Power Ratio Calculation Using Dual-energy Computed Tomography With Fast Kilovoltage Switching for Treatment Planning of Particle Therapy
复制标题
DOI：
10.21873/invivo.12681
复制
发表时间：
2022-01-01
期刊：
影响因子：
2.3
通讯作者：
Konishi, Koji
中科院分区：
文献类型：
--
作者：
Ohira, Shingo;Imai, Yasuhiro;Konishi, Koji
背景/目的：评价快速千伏切换双能计算机断层扫描(FKSCT)在粒子治疗中停止功率比(SPR)计算的准确性。材料与方法：扫描含有不同参照物的组织特征体模，获得77keV(VMI77keV)和140keV(VMI140keV)的单能量CT图像，生成虚拟单色图像，水密度(WD)图像和有效Z(Z(Ef))图像。对于SECT，生成VMI77keV和VMI140keV查找表，以将测量的Hounsfield值转换为正常体模大小的理论SPR。随后，在小模体和大模体中扫描标准物质。SPR是使用SECT(SPRSECT)图像、VMI77keV(SPR77keV)和VMI140keV(SPR140keV)的查找表计算的，它是从WD和ZJeff(SPRWD)得出的。结果：在正常大小的体模中，SPRWD与理论SPR的总体平均误差为-0.3%，大多数参考物质的SPRWD与理论SPR的平均值保持在2%以下。对于大型体模，标准物质的SPR140keV(3.0%，p=0.006)和SPRWD(3.2%，p=0.002)的总体平均绝对差值显著低于SPRSECT(5.9%)。对于小体模，SPR77keV(1.0%，p=0.001)和SPR140keV(1.1%，p=0.013)与SPRSECT(2.2%)相比，SPR计算的平均差异显著减小。结论：与SECT相比，FKSCT产生的VMI140keV显著提高了SPR的估计精度。因此，FKSCT可用于提高粒子治疗计划的剂量计算精度。
Background/Aim: This study evaluated the calculation accuracy of the stopping power ratio (SPR) using dual-energy computed tomography with fast kilovoltage switching (FKSCT) for particle therapy.Materials and Methods: A tissue characterization phantom with various reference materials was scanned to obtain single-energy computed tomography (SECT) images and generate virtual monochromatic images at 77 keV (VMI77keV) and 140 keV (VMI140keV), water density (WD) images, and effective Z (Z(eff)) images. For SECT, VMI77keV and VMI140keV lookup tables were generated to convert the measured Hounsfield value into the theoretical SPR for a normal phantom size. Subsequently, the reference materials were scanned in small and large phantoms. The SPR was calculated using the lookup tables of SECT (SPRSECT) images, VMI77keV (SPR77keV), and VMI140keV (SPR140keV), and it was derived from the WD and Zeff (SPRWD). Results: In the normal-sized phantom, the overall mean difference between SPRWD and theoretical SPR was -0.3%, and remained below 2% for most reference materials. For the large phantom, the overall mean absolute difference for SPR140keV (3.0%, p=0.006) and SPRWD (3.2%, p=0.002) for the reference materials was significantly lower than that for SPRSECT (5.9%). For the small phantom, a significant reduction in the mean difference in the SPR calculation was observed in SPR77keV (1.0%, p=0.001) and SPR140keV (1.1%, p=0.013) compared with SPRSECT (2.2%). Conclusion: VMI140keV generated using FKSCT significantly improves the estimation accuracy of SPR compared with SECT. Thus, FKSCT may be used to improve the dose calculation accuracy for treatment planning of particle therapy.