非均整器模式在左侧乳腺癌改良根治术后患者深吸气屏气容积旋转调强放疗中的剂量学优势

Dosimetric advantages of flattening filter free technique in deep inspiration breath-hold treatments of left-sided breast cancer after modified radical mastectomy with volumetric modulated arc therapy

目的比较非均整器(FFF)模式和均整器(FF)模式在左侧乳腺癌改良根治术后深吸气屏气(DIBH)动态容积旋转调强放疗(VMAT)中的剂量学差异。方法回顾性分析2020年12月至2021年5月在西安交通大学第一附属医院行DIBH放疗的16例左侧乳腺癌改良根治术后女性患者的临床资料,年龄37~61(43.5±5.7)岁。对同一患者分别设计FFF和FF模式的VMAT计划,给予计划靶区(PTV)相同的处方剂量50 Gy/25次,在达到相同的剂量归一条件下,比较靶区剂量学、危及器官受量及机器执行效率的差异。组间数据比较采用配对t检验。结果2种模式下靶区PTV的D_(2%)、D_(50%)、D_(98%)(Dx%表示x%靶体积的受照剂量)、适形指数、平均指数及梯度指数差异均无统计学意义(t=−1.519~1.644,均P>0.05);FFF模式的心脏V_(5 Gy)、V_(30 Gy)(Vx Gy表示≥x Gy体积占总体积的百分比)及平均剂量(D_(mean)),患侧肺V_(5 Gy)、V_(10 Gy)及D_(mean),全肺V_(5 Gy)、V_(10 Gy)、V20 Gy及D_(mean),患者受照剂量的V_(5 Gy)均优于FF模式,组间比较差异均有统计学意义(t=−4.741~−2.156,均P<0.05);FFF模式机器跳数是FF模式的1.32倍[(1073.41±143.79)MU对(815.70±87.69)MU],但执行时间却减少为FF模式的88.9%[(128.00±11.64)s对(144.75±11.45)s],且差异均有统计学意义(t=8.665、−4.373,均P<0.05)。结论2种模式下靶区剂量相似,FFF模式危及器官受照剂量更低,并且可显著缩短DIBH治疗时间。

Objective To compare the dosimetry difference between flattening filter free(FFF)mode and flattening filter(FF)mode in deep inspiration breath-hold(DIBH)treatments of leftsided breast cancer after modified radical mastectomy with volumetric modulated arc therapy(VMAT).Methods Retrospectively analyzed the clinical data of 16 female patients with left breast cancer after modified radical mastectomy with DIBH radiotherapy in the First Affiliated Hospital of Xi'an Jiaotong University from December 2020 to May 2021,aged 37 to 61(43.5±5.7)years old.VMAT plans of FFF and FF modes were designed for the same patient,and the same prescription dose of 50 Gy/25 times was set in the planning target volume(PTV).Under the same dose normalization,the dosimetric parameters of the target and the organs at risk(OAR)and treatment efficiency were compared between the two plans.Paired t-test was used to compare the data between groups.Results No significant differences in D_(2%),D_(50%),D_(98%),CI,HI and GI were found in the target area between the two modes(t=−1.519-1.644;all P>0.05).FFF mode was superior to FF mode in protection of OAR,such as V_(5 Gy),V_(30 Gy)(Vx Gy:≥x Gy volume as a percentage of total volume)and mean dose(D_(mean))of heart;V_(5 Gy),V_(10 Gy)and D_(mean)of ipsilateral lung;V_(5 Gy),V_(10 Gy),V20 Gy and D_(mean)of whole lung;and V_(5 Gy)of patient dose,and the differences between the two modes were statistically significant(t=−4.741 to−2.156;all P<0.05).The total monitor units of FFF mode was 1.32 times of that in FF mode((1073.41±143.79)MU vs.(815.70±87.69)MU),but the total delivery time was reduced to 88.9%of that in FF mode((128.00±11.64)s vs.(144.75±11.45)s),and the differences between the two modes were statistically significant(t=8.665,−4.373;both P<0.05).Conclusion The target dose between the two modes were similar.The FFF mode can remarkably reduce the radiation dose of OAR and normal tissues,and can significantly shorten the time of DIBH therapy.