心肺运动对心脏立体定向放射治疗的剂量学影响

Dosimetric effects of cardiac-respiratory motion on cardiac stereotactic body radiotherapy

目的:探究心脏立体定向放射治疗(CSBRT)中复杂心肺联合运动带来的剂量学影响。方法:使用心脏运动模体模拟10例患者特异性心肺运动,将模体运动状态下的测量剂量与患者临床放疗计划计算剂量进行比较。此外再模拟18组基于设计的心肺运动,用胶片测量并比较模体运动和静止状态下的辐射剂量。结果:在患者特异性心肺运动组别中,测量剂量与计算剂量间的3%/2 mm标准γ通过率为90.0%±7.0%,头脚方向的呼吸运动幅度与γ通过率的相关性系数为-0.86(P=0.01)。基于设计的心肺运动组别中,心肺运动幅度增大会导致动态剂量和静态参考剂量间的一致性降低,其中呼吸运动幅度带来的影响最明显,随其增大,呼吸运动方向90%等剂量宽度减小,平均斜率为-1.6;半影增加,平均斜率为1.4。结论:呼吸运动幅度是影响CBSRT剂量精度的主要因素。心肺运动特征及其产生的剂量学影响具有患者间特异性,有必要在CSBRT治疗前对患者进行心肺运动特征评估,个性化地使用运动管理技术以提高治疗精度。

Objective To investigate the dosimetric effects of complex cardiac-respiratory motion in cardiac stereotactic body radiotherapy(CSBRT).Methods A cardiac motion phantom was employed to simulate patient-specific cardiac-respiratory motion in 10 cases.The measured doses obtained under the phantom motion state were compared with the calculated doses in radiotherapy treatment planning for clinical patients.Moreover,18 groups of design-based cardiac-respiratory motion were simulated.The radiation doses under the phantom motion state were measured using radiochromic films and compared with those under the resting state.Results In the patient-specific cardiac-respiratory motion group,the gamma passing rate(GPR)under the 3%/2 mm standard between the measured and the calculated doses was 90.0%±7.0%.The correlation coefficient of the respiratory motion amplitude in the superior-inferior(SI)dimension with the GPR was-0.86(P=0.01).In the design-based cardiac-respiratory motion groups,the increase in the amplitude of cardiac-respiratory motion reduced the consistency between the dynamic dose and the static reference dose.Especially,the increase in the respiratory motion amplitude produced the most pronounced effect,reducing the width of the 90%isodose line in the respiratory motion direction,with a mean slope of-1.6.Additionally,the increase in the penumbra corresponds to a mean slope of 1.4.Conclusions The respiratory motion amplitude serves as a primary factor influencing the dose accuracy of CBSRT.The characteristics and dosimetric effects of cardiac-respiratory motion are patient-specific,thus necessitating the assessment of cardiac-respiratory motion characteristics before CBSRT to individualize the application of motion management techniques for enhanced treatment accuracy.