影响调强放疗绝对剂量的主要因素及应对措施

Main Influent Factors on Absolute Dose of Intensity-Modulated Radiation Therapy and Countermeasures

目的:验证调强放射治疗的绝对剂量误差,探索影响调强放疗绝对剂量的因素及其应对措施。方法:将20例准备实施调强放疗病人的实际治疗计划,用标准水模体进行计划移植,生成验证计划并计算体模内电离室测量点的计划剂量,执行验证计划的照射,用电离室进行实际物理绝对剂量测量,计算实际测量剂量值和计划剂量值的百分相对误差。分析影响调强放疗绝对剂量误差的主要因素,采取相应改进措施,验证另80例调强放疗的绝对剂量,比较前20例与改进后80例调强放疗绝对剂量验证结果。结果:前20例调强放疗绝对剂量百分相对误差分布范围是-8.00%～5.00%,平均误差为-2.01%,标准差为3.55%。采取相应改进措施后,80例调强放疗绝对剂量百分相对误差全部在4.4%以内,分布范围缩小到-4.4%～2.5%,平均误差为-1.49%,比前20例平均误差下降25.9%,标准差为1.40%,比前20例下降60.6%。结论:分析影响调强放疗绝对剂量的因素,采取必要的应对措施,能够有效提高调强放射治疗绝对剂量的准确性。

Objective： To verify the absolute dose accuracy of IMRT and explore the Main influent factors on absolute dose of intensity-modulated radiated therapy and countermeasures. Methods： Conducting hybrid plans using phantom geometry and 20 eases patient＇s incident beam fluence for IMRT. Irradiation dose were measured by ionization chamber to verify the absolute dose accuracy oflMRT, calculate the relative difference between measured dose and planned dose. Analyzing the main influent factors on absolute dose of IMRT and taking some countermeasures, verify the absolute dose accuracy of IMRT for another 80 eases. Compare the result of absolute dose verification between the first 20 cases and the improving 80 cases. Results： Relative difference between measured dose and planned dose are within -8.00%-5.00% for first 20cases, average difference was -2.01%, standard deviation was 3.55%. After take some improving countermeasures, relative difference between measured dose and planned dose are within -4.4%-2.5% for 80cases, average difference was -1.49%,decreased 25.9%, standard deviation was 1.40%, decreased 60.6%. Conclusion： It is efficient to improve the absolute dose accuracy of IMRT by analyzing the main influent factors on absolute dose of intensity-modulated radiation therapy and taking some countermeasures.