摘要
目的:研究Monaco系统中高密度介质对吸收剂量的影响,并提出保护高密度介质的计划设计方案。方法:选取50例头颈部、胸部、腹部、盆腔部和骨组织肿瘤患者(各10例)作为研究对象,从其CT图像中获取不同密度介质的相对电子密度信息,在Monaco系统中采用传统的“基于介质”的剂量计算方法得到初始的剂量分布,然后在不改变其他优化条件的情况下,采用“基于水”的剂量计算方法得到新的剂量分布。统计2种方法计算的相对剂量差异,并采用直方图统计得到相对电子密度与2种方法计算的相对剂量差异之间的关系。对10例头颈部肿瘤患者设计保护高密度介质下颌骨的治疗计划,并比较原计划与保护下颌骨的计划的适形性指数(conformity index,CI)和下颌骨的最大剂量。采用SPSS 22.0进行统计学分析。结果:2种方法计算的相对剂量差异在低密度介质中很小,而在高密度介质中较大,其中骨皮质的相对剂量差异最大。2种方法计算的5个肿瘤部位的相对剂量差异与相对电子密度的关系曲线基本一致,均呈凹形。保护下颌骨的计划和原计划相比,CI差异无统计学意义,但下颌骨的最大剂量降低了5.23 Gy(P<0.05)。结论:对于高密度介质,采用“基于水”和“基于介质”的2种剂量计算方法计算剂量会产生不可忽略的剂量学差异。设计保护高密度介质下颌骨的计划,可在不影响靶区适形性的情况下有效降低下颌骨的最大剂量。
Objective To study the effect of high-density media on absorbed dose in Monaco system and to propose a plan design scheme to protect high-density media.Methods Fifty patients with head and neck,chest,abdomen,pelvis and bone tumors(10 patients each)were selected as the study subjects,and the relative electron density information of different density media was obtained from their CT images.The initial dose distribution data were got by the conventional"medium-based"dose calculation method in Monaco system,and then the new data were aquired by the"water-based"dose calculation method without changing other optimization conditions.The relative dose difference between the two methods was calculated,and the relationship between the relative electron density and the relative dose difference between the two methods was determined by histogram statistics.A treatment plan to protect the mandible with high-density media was designed for 10 patients with head and neck tumors,and the conformity index(CI)and the maximum dose to the mandible were compared between the original plan and the plan to protect the mandible.SPSS 22.0 was used for statistical analysis.Results The relative dose differences calculated by the 2 methods were small in the low-density medium and large in the high-density medium,with the largest relative dose difference in the bone cortex.The curves of relative dose difference versus relative electron density calculated by the 2 methods for the 5 tumor sites were generally consistent and concave in shape.The difference in CI was not statistically significant for the plan to protect the mandible compared with the original plan,while the maximum dose to the mandible was reduced by 5.23 Gy(P<0.05).Conclusion For high-density media,there are significant dosimetric differences between the"water-based"and"media-based"dose calculation methods.A plan to protect the mandible from high-density media can effectively reduce the maximum dose to the mandible without affecting the conformability of the target area.
作者
许六军
张建英
李婷婷
张玉洁
XU Liu-jun;ZHANG Jian-ying;LI Ting-ting;ZHANG Yu-jie(Department of Radiotherapy,Zhongshan Hospital of Fudan University,Shanghai 200032,China)
出处
《医疗卫生装备》
CAS
2022年第9期40-44,共5页
Chinese Medical Equipment Journal
关键词
高密度介质
基于水
基于介质
剂量学
相对电子密度
high-density medium
water-based
media-based
dosimetry
relative electron density
