Assessment of individual organ doses in a realistic human phantom from neutron and gamma stimulated spectroscopy of the breast and liver.
Assessment of individual organ doses in a realistic human phantom from neutron and gamma stimulated spectroscopy of the breast and liver.
复制标题
通过中子和伽马刺激的乳房和肝脏光谱评估真实人体模型中的各个器官剂量。
DOI：
10.1118/1.4873684
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发表时间：
2014
期刊：
影响因子：
3.8
通讯作者：
Kapadia,AnujJ
中科院分区：
文献类型：
--
作者：
Belley,MatthewD;Segars,WilliamPaul;Kapadia,AnujJ
目的在考虑使用电离诊断成像测试进行临床诊断和筛查时，了解患者的辐射剂量至关重要。作者使用蒙特卡罗模拟，估计了男性肝脏、女性肝脏和女性乳房的中子和伽马辐射的三维器官剂量分布，以进行中子和伽马刺激光谱成像。方法蒙特卡罗模拟是使用 Geant4 GATE 应用程序和体素化 XCAT 人体模型开发的。将男性和女性全身 XCAT 模型体素化为 256 × 256 × 600 体素 (3.125 × 3.125 × 3.125 mm3)。将 5.0 MeV 中子或 7.0 MeV 光子的单能矩形束入射到 2 厘米厚的模型切片上。光束围绕模型旋转八个不同的角度，范围从 0° 到 180°。计算体内各个器官的吸收剂量，并计算剂量体积直方图以分析每个器官的绝对剂量和相对剂量。结果肝脏的中子照射显示肝脏的器官剂量吸收最高，其他近端器官的剂量明显较低。随着沿光束路径深度的增加，受照射切片内的剂量分布表现出显着的衰减，在光束出口侧衰减至最大值的~15%。肝脏的伽马射线照射使胃壁受到最高的器官剂量。伽马射线的剂量分布显示，在射束入口处有一个剂量累积区域，随后所有深层组织结构的剂量分布相对均匀，在射束出口侧衰减至最大值的约 75%。对于乳房扫描，中子和伽马射线照射都记录了乳房中的最大器官剂量，所有其他器官接受的剂量不到乳房剂量的 1%。中子扫描的有效剂量范围为 0.22 至 0.37 mSv，伽马扫描的有效剂量范围为 41 至 66 mSv。 结论 主要靶器官的中子和伽马辐照被发现将总剂量的大部分传递给射束平面内的主要目标器官（和其他大型器官），而射束外的近端器官则受到相当低的剂量。这些结果还表明，尽管使用了中子等高散射粒子，但中子受激发射计算机断层扫描的剂量与其他临床成像技术（如 X 射线计算机断层扫描 (X 射线 CT)）相当。鉴于中子扫描期间器官剂量的高度不均匀性，在计算中子照射的平均剂量时必须小心。中子扫描的有效剂量与 X 射线 CT 相当。需要进一步改进技术以降低伽马扫描的有效剂量水平。
PurposeUnderstanding the radiation dose to a patient is essential when considering the use of an ionizing diagnostic imaging test for clinical diagnosis and screening. Using Monte Carlo simulations, the authors estimated the three‐dimensional organ‐dose distribution from neutron and gamma irradiation of the male liver, female liver, and female breasts for neutron‐ and gamma‐stimulated spectroscopic imaging.MethodsMonte Carlo simulations were developed using the Geant4 GATE application and a voxelized XCAT human phantom. A male and a female whole body XCAT phantom was voxelized into 256 × 256 × 600 voxels (3.125 × 3.125 × 3.125 mm3). A monoenergetic rectangular beam of 5.0 MeV neutrons or 7.0 MeV photons was made incident on a 2 cm thick slice of the phantom. The beam was rotated at eight different angles around the phantom ranging from 0° to 180°. Absorbed dose was calculated for each individual organ in the body and dose volume histograms were computed to analyze the absolute and relative doses in each organ.ResultsThe neutron irradiations of the liver showed the highest organ dose absorption in the liver, with appreciably lower doses in other proximal organs. The dose distribution within the irradiated slice exhibited substantial attenuation with increasing depth along the beam path, attenuating to ∼15% of the maximum value at the beam exit side. The gamma irradiation of the liver imparted the highest organ dose to the stomach wall. The dose distribution from the gammas showed a region of dose buildup at the beam entrance, followed by a relatively uniform dose distribution to all of the deep tissue structures, attenuating to ∼75% of the maximum value at the beam exit side. For the breast scans, both the neutron and gamma irradiation registered maximum organ doses in the breasts, with all other organs receiving less than 1% of the breast dose. Effective doses ranged from 0.22 to 0.37 mSv for the neutron scans and 41 to 66 mSv for the gamma scans.ConclusionsNeutron and gamma irradiation of a primary target organ was found to impart the majority of the total dose to the primary target organ (and other large organs) within the beam plane and considerably lower dose to proximal organs outside of the beam. These results also indicate that despite the use of a highly scattering particle such as a neutron, the dose from neutron stimulated emission computed tomography scans is on par with other clinical imaging techniques such as x‐ray computed tomography (x‐ray CT). Given the high nonuniformity in the dose across an organ during the neutron scan, care must be taken when computing average doses from neutron irradiations. The effective doses from neutron scanning were found to be comparable to x‐ray CT. Further technique modifications are needed to reduce the effective dose levels from the gamma scans.
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