TrueBeam加速器射野准直器跟随功能在鼻咽癌固定野调强放疗和容积旋转调强放疗中的应用’

目的：研究TrueBeam加速器的射野跟随功能在鼻咽癌固定野调强放疗和容积旋转调强放疗中的作用；方法：随机选取10例鼻咽癌患者．分别对每位患者设计四个计划．分别为固定野调强组的dIMRT-JT和dlMRT计划，容积旋转调强组的RapidArc—JT和RapidArc计划。dIMRT-JT和RapidAre-JT为使用射野跟随功能的计划，dIMRT和RapidArc为不使用射野跟随功能的计划。分别比较使用和不使用射野跟随功能的治疗计划．患者靶区和危及器官的剂量学差异；结果：固定野调强计划，在使用和不使用射野准直器跟随功能，其靶区的剂量学参数差别不大，但是脑干、脊髓、晶状体、腮腺等危及器官都有较大改善，脑干和脊髓的D，。剂量分别降低了3．3％和4．2％，左、右两侧晶状体的D。剂量分别降低了38．7％和40．6％，左、右两侧腮腺的平均剂量D一分别降低了6．3％和6．4％；P〈0．05，有统计学意义。容积旋转调强计划，在使用和不适用射野准直器跟随功能时，靶区和脑干、脊髓及腮腺等危及器官的剂量学差异很小，没有统计学意义；而左、右两侧晶状体的D。剂量分别降低了6．9％和7．2％；结论：鼻咽癌固定野调强放疗和容积旋转调强放疗中，使用TrueBeam加速器的射野准直器跟随功能，可以在保证靶区剂量分布不变的前提下，降低危及器官的受照剂量。尤其在固定野调强放疗中，使用射野准直器跟随功能的计划其剂量学优势非常明显。

Application of TrueBeam Jaw-tracking Function in Fix Gantry IMRT and VMAT for NPC

Objective： To study the Jaw-tracking function of TrueBeam in fixed gantry IMRT and VMAT.Methods： 10 NPC patients were selected in this study. 4 treatment plans were designed for each patient. There were two fix gantry IMRT plans and two VMAT plans, one IMRT plan and VMAT plan using Jaw-tracking function were marked with dlMRT-JT and RapidArc-JT. The other two plans were dlMRT and RapidArc plan. The differences of dose distribution for Targets and OARs were compared. Results： For fix gantry IMRT plan group, there was almost no difference between dlMRT-JT and dlMRT plans for Targets dose. But the dose distributions for Brian stem, Spinal cord, Lens and Parotids were greatly improved. P〈0.05, there was statistical significant. The D~ dose of dlMRT-JT plans for Brian stem and Spinal cord was 3.3% and 4.2% lower than dlMRT plan. The D~ dose for left and right Lens was reduced by 38.7% and 40.6% for dlMRT-JT Plans compared to dIMRT plans. 6.3% and 6.4% of the D~dose for left and right Parotids were reduced in dlMRT-JT plans. For VMAT plan group, there was almost no difference for the dose of targets, Brain stem, Spinal cord and Parotids between RapidArc-JT and RapidArc plans. But the Dmax dose for left and right Lens were reduced by 6.9% and 7.2% in RapidArc-JT plans. Conclusions： The Jaw-tracking fimction in TrueBeam machine could be used in IMRT and VMAT plans to reduce the dose of OARs. There was dosimetric advantage using Jaw-tracking especially in IMRT plans.