半铅门技术在口咽癌调强治疗计划中的剂量学研究

A dosimetric study of half jaw technique applied in the treatment planning for oropharyngeal cancer patients

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摘要目的研究半铅门容积旋转调强计划(H-VMAT)应用于口咽癌时的剂量优势,与全铅门容积旋转调强计划(W-VMAT),固定野调强计划(IMRT)进行比较.方法选取10例口咽癌患者CT图像传至Eclipse11.0(美国Varian公司)治疗计划系统行H-VMAT、W-VMAT和IMRT.两种VMAT计划均采用双弧360°照射,IMRT计划采用7野均分.3种调强计划的通量优化条件一样.统计靶区PGTV、PCTV1、PCTV2、PGTVln、PCTVln的D2、D98、D50、均匀性指数(HI)、适形指数(CI);脑干、脊髓的D1 cc;腮腺、口腔、喉的平均剂量Dmean,颈部正常组织Dmean,跳数(MU)以及其他剂量学参数.结果 3种调强计划方式之间比较,H-VAMT计划改善了靶区的HI、CI(靶区PCTV2除外),差异具有统计学意义(HI:F=3.959、6.764、10.581、6.770、13.040,P<0.05;CI:F=6.594、4.138、0.842、4.031、5.388,P<0.05),同时明显降低了脑干、脊髓的Dmax(F=4.509、20.331,P<0.05)和D1 cc(F=27.432、26.314,P<0.05),减少了口腔、喉以及颈部正常组织的Dmean(F=4.279、29.498、19.295,P<0.05),其中口腔、喉的V50％在IMRT中略低(F=8.140,P<0.05).IMRT对口腔、喉的保护略优于W-VMAT,但剂量分布最差.H-VMAT计划在颈部正常组织以及下颈,背部的剂量分布最优,IMRT则存在高剂量曲线.结论口咽癌容积旋转调强计划采用半铅门技术优于全铅门W-VMAT、固定野IMRT计划,可以考虑临床实践.

abstractsObjective To investigate the potential dosimetric advantages of half jaw volumetric modulated arc therapy ( H-VMAT) applied to the Oropharyngeal Cancer, comparing with full jaw VMAT (F-VMAT) and intensity modulated radiotherapy ( IMRT ). Methods Planning CT images of 10 oropharyngeal cancer patients were retrospectively chosen and transferred to Eclipse treatment planning system v. 11. 0 (Varian Medical Systems, Pala Alto, USA), based on which H-VMAT, W-VMAT, and IMRT plans were created. Two full arcs (360°) were adopted for VMAT planning, and the 7 beams were equally distributed for IMRT planning. The optimization constraints remained the same for the three kinds of plans. The dosimetric parameters such as D2 , D98 , D50 , HI, and CI were evaluated for PGTV, PCTV1, PCTV2, PGTVln, and PCTVln. In addition, the maximum dose (Dmax) and D1 cc(minimum dose received by 1cc) of the brainstem and spinal cord were analyzed respectively. The mean dose ( Dmean ) to the parotids, oral cave, larynx, and cervical normal tissues were also reviewed. The monitor units ( MU) for all treatment plans were recorded. Results Comparisons of the three planning techniques showed that H-VAMT improved the HI and CI of the targets (except PCTV2) significantly (HI: F =3. 959, 6. 764, 10. 581, 6. 770, 13. 040, P<0. 05;CI:F=6. 594, 4. 138, 0. 842, 4. 031, 5. 388, P<0. 05);reduced Dmax(F=4. 509, 20. 331, P<0. 05) and D1 cc for brainstem and spinal cord (F=27. 432, 26. 314, P<0. 05) significantly;reduced Dmean(F=4. 279, 29. 498, 19. 295, P<0. 05) to the normal tissues of the mouth, throat and neck significantly. The V50 of the mouth and throat were slightly lower in IMRT plans (F=8. 140, P<0. 05). IMRT was slightly better than W-VMAT in sparing oral cavity and larynx, but the dose distribution was the worst. The H-VMAT plans showed the best dose distribution in the cervical normal tissues, especially for the lower and posterior parts, where IMRT plans displayed high dose curves. Conclusions H-VMAT is dosimetrically superior than W-VMAT and IMRT for oropharyngeal cancer, which could be considered for clinical applications.