Nuclear-interaction correction for patient dose calculations in treatment planning of helium-, carbon-, oxygen-, and neon-ion beams
Nuclear-interaction correction for patient dose calculations in treatment planning of helium-, carbon-, oxygen-, and neon-ion beams
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DOI：
10.1088/1361-6560/ab5fee
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发表时间：
2020-01-01
影响因子：
3.5
通讯作者：
Shirai, Toshiyuki
中科院分区：
文献类型：
--
作者：
Inaniwa, Taku;Lee, Sung Hyun;Shirai, Toshiyuki
在带电粒子疗法治疗计划中，患者通常被建模为可变密度水，即停止有效密度rho（S），并且在水中测量的平面积分剂量分布（PID）被应用于基于用rho（S）缩放的路径长度的患者剂量计算。这种近似保证了带电粒子束的射程精度。然而，它会导致剂量计算错误，由于水的非等效性的身体组织的核相互作用起源于成分的差异。我们以前提出并验证了一种PID校正方法的误差在碳离子放射治疗。在本研究中，我们验证了氦，氧，氦离子束的PID校正方法。建立了氦、碳、氧和氦离子束的ρ（S）与人体组织核有效密度ρ（N）的一一对应关系，并用于校正PID，以考虑患者剂量计算的误差。用非扫描和扫描离子束对非水材料的校正方法进行了测试。在未扫描的光束穿透材料，剂量计算误差高达5.9%，观察到在布拉格峰区，而他们被减小到0.9%的PID校正方法。在扫描光束穿透橄榄油，剂量计算误差高达2.7%的平均超过了扩展的布拉格峰观察，而他们被降低到0.4%的校正方法。为了研究身体组织的水非等效性对肿瘤剂量的影响，我们对前列腺和子宫病例进行了治疗计划研究。在子宫病例中观察到氦、碳、氧和氦离子束的肿瘤过量剂量分别为0.9%、1.8%、2.0%和2.2%。这些剂量误差可以通过PID校正方法来减小。目前的结果表明，PID校正方法是简单，实用，准确的治疗计划，这四种离子。
In charged-particle therapy treatment planning, the patient is conventionally modeled as variable-density water, i.e. stopping effective density rho(S), and the planar integrated dose distribution measured in water (PID) is applied for patient dose calculation based on path length scaling with the rho(S). This approximation assures the range accuracy of charged-particle beams. However, it causes dose calculation errors due to water nonequivalence of body tissues in nuclear interactions originating from compositional differences. We had previously proposed and validated a PID correction method for the errors in carbon-ion radiotherapy. In the present study, we verify the PID correction method for helium-, oxygen-, and neon-ion beams. The one-to-one relationships between rho(S) and the nuclear effective density rho(N) of body tissues were constructed for helium-, carbon-, oxygen-, and neon-ion beams, and were used to correct the PIDs to account for the dose calculation errors in patient. The correction method was tested for non-water materials with un-scanned and scanned ion beams. In un-scanned beams penetrating the materials, the dose calculation errors of up to 5.9% were observed at the Bragg peak region, while they were reduced to 0.9% by the PID correction method. In scanned beams penetrating olive oil, the dose calculation errors of up to 2.7% averaged over the spread-out Bragg peak were observed, while they were reduced to 0.4% by the correction method. To investigate the influence of water nonequivalence of body tissues on tumor dose, we carried out a treatment planning study for prostate and uterine cases. The tumor over-doses of 0.9%, 1.8%, 2.0%, and 2.2% were observed in the uterine case for the helium-, carbon-, oxygen-, and neon-ion beams, respectively. These dose errors could be diminished by the PID correction method. The present results verify that the PID correction method is simple, practical, and accurate for treatment planning of these four ion species.