Analysis of dosimetric verification results of stereotactic body radiotherapy

Q4 Medicine

中华放射医学与防护杂志 Pub Date : 2019-09-25 DOI:10.3760/CMA.J.ISSN.0254-5098.2019.09.008

Xile Zhang, R. Yang, Jun Li, Daojian An, Jiaqi Li, Junjie Wang

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引用次数: 1

Abstract

Objective To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy (SBRT) plans, and to investigate the sensitivity of the result to three factors: interpolation of measured data, size of dose calculation grid and assessment threshold. Methods The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation (1.00 mm) and non-interpolation (7.62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i. e., 1.0 mm, 2.5 mm and 4.0 mm were compared respectively. The threshold of dose assessment was selected as 10%, 20% and 30%, respectively. Three criteria of γ analysis were selected: 2%/2 mm, 3%/2 mm and 3%/3 mm. Results Under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, the average γ passing rates were (86.3±7.3)% and (93.7±5.6)%, (94.1±4.4)% and(97.7±3.9)%, (97.7 ±2.2)% and (99.1±1.7)%, respectively, with and without linear interpolation. Relative to the 1.0 mm reference grid, the grids of 2.5 mm and 4.0 mm significantly decreased γ passing rates by 3.8%, 1.9%, 0.8% (t=8.41, 9.06, 5.30, P<0.05) and by 6.5%, 6.0%, 3.5% (t=-13.76, -13.15, -9.80, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively. Relative to the 10% reference threshold, the shresholds of 20% and 30% significantly decreased γ passing rates by 2.4%, 1.0%, 0.6%(t=-8.60, -5.86, -4.68, P<0.05) and by 4.0%, 1.7%, 0.9% (t=-9.45, -6.66, -5.06, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively. Conclusions Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients. Key words: Stereotactic body radiotherapy; Dosimetric verification; Interpolation; Dose calculation grid size; Dose assessment threshold

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立体定向放射治疗剂量学验证结果分析

目的分析立体定向体放射治疗(SBRT)方案患者特异性剂量学验证结果，探讨结果对测量数据插值、剂量计算网格大小和评估阈值三个因素的敏感性。方法回顾性分析50例患者SBRT计划的剂量学验证结果，评价以下因素的影响。测量数据分别采用线性插值(1.00 mm)和非插值(7.62 mm)处理。比较Eclipse规划系统中1.0 mm、2.5 mm和4.0 mm三种剂量计算网格尺寸。剂量评估阈值分别为10%、20%和30%。γ分析选择了三个标准:2%/ 2mm、3%/ 2mm和3%/ 3mm。结果在2%/ 2mm、3%/ 2mm和3%/ 3mm标准下，加线性插值和不加线性插值的γ平均合格率分别为(86.3±7.3)%和(93.7±5.6)%、(94.1±4.4)%和(97.7±3.9)%、(97.7±2.2)%和(99.1±1.7)%。与1.0 mm栅格相比，2.5 mm栅格和4.0 mm栅格在2%/2 mm、3%/2 mm和3%/3 mm标准下的γ通过率分别显著降低3.8%、1.9%、0.8% (t=8.41、9.06、5.30,P<0.05)和6.5%、6.0%、3.5% (t=-13.76、-13.15、-9.80,P<0.05)。在2%/2 mm、3%/2 mm和3%/3 mm标准下，20%和30%阈值分别显著降低了2.4%、1.0%、0.6%(t=-8.60、-5.86、-4.68,P<0.05)和4.0%、1.7%、0.9% (t=-9.45、-6.66、-5.06,P<0.05)的γ通过率。结论插值、剂量计算网格大小和剂量评估阈值是影响剂量验证结果的因素，在对立体定向放疗患者进行剂量学验证时需要考虑。关键词:立体定向放射治疗;剂量测定的鉴证;插值;剂量计算网格尺寸;剂量评估阈值

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