摘要
目的 针对容积调强旋转放疗技术（VMAT）,分析患者计划验证通过率对多叶准直器（MLC）位置误差的灵敏度.方法 选取6例双弧VMAT计划,引入MLC位置误差（±0.5 mm、±1 mm和±2 mm）,模拟VMAT执行过程中MLC可能出现的系统误差,包括MLC射野宽度误差和MLC整体偏向一侧的误差.每个病例有10个计划,1个原计划和9个带有误差的新计划.利用螺旋形半导体探测阵列（ArcCheck）进行验证测量,得到每个病例原计划和新计划的剂量分布.采用绝对剂量结合等剂量距离差别的计算方法,以原计划计算剂量分布为参考,分别得到每个计划的通过率.结果 当评价指标为3％/3 mm时,6例原计划的平均通过率为96％,带有＋1 mm、＋2 mm、-2 mm射野宽度误差的计划和2 mm MLC整体偏向一侧误差的计划平均通过率下降8.8％、15.5％、6.1％和7.9％,这些MLC位置误差通过计划验证可以检测到,其他MLC位置误差对计划通过率影响小,无法检测到.2％/2 mm评价指标较3％/3 mm对MLC位置误差更敏感.结论 对于1 mm以内的MLC位置误差,VMAT计划的验证对其不敏感.为保证VMAT计划执行的准确性,需要针对MLC做专门的质量控制.
Objective To evaluate the sensitivity of patient-specific volumetric-modulated arc therapy （VMAT） quality assurance （QA） to minor multileaf collimator （M LC） positioning errors.Methods Systematic multileaf collimator （MLC） positioning errors （＋0.5 mm,＋ 1 mm and ＋2 mm） were introduced into the clinical VMAT patient plans with 2 types of MLC positioning errors：systematic MLC gap width errors and systematic MLC shift errors for 6 cases,including 3 cases with prostatic cancer and 3 cases with nasopharyngeal cancer.The planar dose distributions of the original and modified plans were measured using ArcCheck array.The coincidence between the measured results and the calculated results was evaluated using both absolute distance-to-agreement （AD-DTA） analysis with 3%/3 mm and 2%/2 mm criteria.Results The average passing rate of the 6 original VMAT plans was 96.0% with the ADDTA criteria of 3%/3 mm which was commonly adopted in clinical practice.For the MLC gap width errors of ＋ 1 mm,＋2 mm,and-2 mm and the MLC shift errors of 2 mm,the drop levels in average passing rate with the AD-DTA criteria of 3%/3 mm were 8.8%,15.5%,6.1% and 7.9%,respectively.The ＋ 2 mm MLC positioning errors and ＋ 1 mm MLC gap width errors could be detected by the patient-specific VMAT QA procedure.The AD-DTA criteria of 2%/2 mm was more sensitive compared with the criteria of 3%/3 mm.Conclusions Patient-specific VMAT QA is not sensitive enough to detect the systematic MLC positioning errors within 1 mm.Additional MLC QA is needed to guarantee the accuracy of VMAT delivery.
出处
《中华放射医学与防护杂志》
CAS
CSCD
北大核心
2013年第4期388-391,共4页
Chinese Journal of Radiological Medicine and Protection
基金
国家自然科学基金（10975187）
关键词
容积调强旋转放疗
计划验证
多叶准直器
位置误差
通过率
Volumetric-modulated arc therapy （ VMAT ）
Patient-specific QA
Multileaf collimator （MLC）
Positioning errors
Passing rate
