鼻咽癌放疗中组织特性参数对腮腺受照剂量的影响研究

Influence of tissue characteristic parameter to parotid gland radiation dose in nasopharyngeal carcinoma radiotherapy

目的:分析鼻咽癌放疗中组织特性参数a值对腮腺受照剂量的影响。方法:随机选取20例接受鼻咽癌调强放疗(intensity-modulated radiotherapy,IMRT)的患者,基于Eclipse 13.6计划系统设计10种不同a值(0.1≤a≤1.0,步长为0.1)的IMRT计划,分析各计划的剂量学参数、机器跳数和出束时间的差异。采用SPSS 20.0软件进行统计学分析。结果:对靶区剂量分布进行归一化处理后,10种IMRT计划的靶区和所有危及器官的剂量学参数均满足临床要求,靶区和除腮腺之外其他各危及器官的剂量学参数未表现出统计学差异(P>0.05);10种计划的机器跳数和出束时间亦未随a值变化而改变(P>0.05);当0.1≤a≤0.3或0.4≤a≤1.0(步长为0.1)时,腮腺各剂量学参数变化趋势不明显(P>0.05),另外,当0.4≤a≤1.0(步长为0.1)时,除腮腺V20之外,腮腺其他各剂量学参数较0.1≤a≤0.3(步长为0.1)时呈减小趋势(P<0.05)。结论:改变a值对除腮腺之外其他剂量学参数影响不明显,合适的a值(0.4≤a≤1.0,步长为0.1)可有效降低腮腺受照剂量,建议在设计鼻咽癌IMRT计划时在该范围内设置a值。

Objective To analyze the influence of tissue characteristic parameter(a values)to the parotid gland radiation dose in nasopharyngeal carcinoma radiotherapy.Methods Twenty patients were randomly selected to receive intensity-modulated radiotherapy(IMRT)for nasopharyngeal carcinoma and 10 IMRT plans with different a values(0.1≤a≤1.0 in step of 0.1)were designed based on the Eclipse 13.6 planning system to analyze the dosimetric parameters,machine units and delivery time of each plan.SPSS 20.0 software was used for statistical analysis.Results The dosimetric parameters of the target area and all organs at risk for the 10 IMRT plans met the clinical requirements after normalizing the dose distribution in the target area,and the dosimetric parameters of the target area and all organs at risk except the parotid gland did not have statistical differences(P>0.05).The machine units and delivery time didn't change with a values for the 10 plans(P>0.05).When 0.1≤a≤0.3 or 0.4≤a≤1.0(in step of 0.1),there was no significant trend(P>0.05)in the parotid dosimetric parameters;when 0.4≤a≤1.0(in step of 0.1),the parotid dosimetric parameters,except for parotid V20,tended to decrease compared with those when 0.1≤a≤0.3(in step of 0.1)(P<0.05).Conclusion Changing the a values does not significantly affect other dosimetric parameters except the parotid gland.An appropriate a value(0.4≤a≤1.0 in step of 0.1)is effective in reducing the radiation dose to the parotid gland and it is recommended that the a value be set within this range when designing an IMRT plan for nasopharyngeal carcinoma.