瓦里安呼吸门控实时位置管理系统对放射治疗计划剂量学的影响

Impact of the Varian real-time position management respiratory gating system on radiotherapy planning dosimetry

目的研究瓦里安呼吸门控实时位置管理(RPM)系统对放射治疗计划剂量学的影响。方法回顾性选取40例胸腹部肿瘤放疗计划,采用质量控制运动模体产生呼吸门控信号,选取呼气末30%~60%稳定时相作为呼吸门控窗,在Edge加速器RPM呼吸门控模式下对上述计划进行Portal Dosimetry(PD)系统剂量验证,采用不同的γ通过率标准进行剂量分析,并分析其γ值的分布特点,与非门控模式下验证结果进行对比。结果在RPM呼吸门控模式下,对于不同均整器模式下的调强放射治疗计划(IMRT)或容积调强放射治疗计划(VMAT),采用γ(3%,3 mm)或(3%,2 mm)标准,所有计划通过率均在95.5%以上,采用更严格的γ(2%,2 mm)标准,所有计划通过率均在90%以上,符合美国医学物理师学会(AAPM)推荐的临床治疗标准。非门控模式下剂量验证结果通过率略优于呼吸门控模式下验证结果,两种模式下差异具有统计学意义(3%/3 mm,Z=-1.45;3%/2 mm,Z=-2.86;2%/2 mm,Z=-3.70;1%/1 mm,Z=-4.52,P<0.05)。两种模式下计划验证结果γ值的最小值、最大值及γ>1.5的份额差异不明显,但非门控模式下γ的平均值及标准偏差总体更小。结论RPM呼吸门控技术引入带来的剂量影响在临床可接受范围内,该门控模式下计划执行是安全可靠的。

Objective To study the impact of the Varian real-time position management(RPM)respiratory gating system on radiotherapy planning dosimetry.Methods The radiotherapy plans of 40 cases with thoracic or abdominal tumors were retrospectively selected in this study.The motion phantom for quality control was adopted to generate respiratory gating signals,and the 30%-60%stable phase at the end of expiratory was selected as the respiratory gating window.The dose verification for the abovementioned radiotherapy plans was performed using the Portal Dosimetry(PD)system under RPM respiratory gating mode with the Edge accelerator.Afterwards,dose analysis was performed with differentγpassing rate criteria and the distribution characteristics ofγvalues were analyzed.Finally,the verification results between the non-gating mode and the gating mode were compared.Results Under the respiratory gating mode,the passing rates of all intensity-modulated radiation therapy/volumetric-modulated arc therapy(IMRT/VMAT)plans with or without flattening filters were over 95.5%byγcriteria of(3%,3 mm)or(3%,2 mm)and were over 90%by stricterγcriteria of(2%,2 mm).All plans met the clinical requirements recommended by the American Association of Physicists in Medicine(AAPM).The passing rates of dose verification under non-gating mode were slightly better than those under respiratory gating mode,and the differences between the two modes were statistically significant(3%/3 mm,Z=-1.45;3%/2 mm,Z=-2.86;2%/2 mm,Z=-3.70;1%/1 mm,Z=-4.52;P<0.05).There was no significant difference in the minimum and maximum values ofγand the share ofγ>1.5 of plan verification result under the two modes.However,the average value and standard deviation of theγwere generally smaller under the non-gating mode.Conclusions The impact of the introduction of RPM respiratory gating technology on dose is clinically acceptable,and the execution of these plans in this gating mode is safe and reliable.