基于两种旋转调强全骨髓照射新技术的研究

Dosimetric Comparison of Total Marrow Irradiation Based on Two Intensity Modulated Arc Therapy

目的:探讨Rapid Arc(RA)容积旋转调强放射治疗与螺旋断层放射治疗(Helical Tomo Therapy,HT)两种旋转调强技术在全骨髓照射中的可行性及剂量学差异。方法:选取8例行全身扫描的患者,采用Eclipse 10.0计划系统自动勾画模块进行靶区勾画并予以适当修改后外放3 mm生成照射靶区,分别设计RA与HT两种旋转调强计划,处方剂量为12 Gy/10 F。通过剂量体积直方图(DVH)、等剂量曲线等参数评价和比较两种治疗计划靶区及危及器官的剂量分布,并评估机器跳数(MU)和出束时间。剂量验证采用Sun Nuclear Arc CHECK系统,通过分析各部位剂量验证通过率评估各自临床实施的安全性及准确性。结果:靶区剂量分布上两种方法均能达到较好的覆盖度且具有类似的适形度(0.54±0.05vs 0.52±0.07,P=0.45),而靶区剂量均匀性HT具有明显的优势(RA/HT的HI值分别为0.19±0.02 vs 0.13±0.02,P=0.00)。在危及器官的保护上,除全脑、口腔、腮腺以及小肠和直肠外,HT均表现出一定的优势。RA/HT两组计划的平均机器跳数和出束时间分别为2566 MU/12293 MU、568 s/875 s。头颈、胸腹、盆腔三部分的计划验证的通过率分别为98.9%±1.9%/94.3%±1.5%、98.4%±1.8%/96.5±1.2%、97.4%±2.1%/94.1%±1.9%。结论:两种旋转调强技术均能较好地实现全骨髓照射且实现射野间的无缝衔接,且RA具有更高的射线利用率,均可应用于全骨髓的临床照射。

Objective To study the feasibility and dosimetric characteristics ofRapidArc （RA） and Tomotherapy （HT） in total marrow irradiation （TMI） for hematologic malignancies. Methods The kVCT data collected from 8 patients were retrospective- ly designed and analyzed for RA and HT. Total bone morrow was contoured as clinical target volume excluding the cubitus and hand parts, then plus a 3.0 mm margin as planning target volume. The prescription dose was 12 Gy in 10 fractions. The plans were evaluated by isodose-curves, dose volume histograms, dose homogeneity indexes, total MU and treatment times. SunNu- clear ArcCHECK system was used for dose verification.The safety and accuracy of clinical delivery were evaluated by the quality assurance of plans. Results The two techniques can well achieve the target coverage. The conformity indices of RA and HT were 0.54＋0.05 and 0.52±0.07 （P=-0.45） respectively, but the HT plans have a visible advantage over the RA plans in the dose uniformity of target. The homogeneity indexes were 0.19± 0.02 and 0.13±0.02 （P=0.00） respectively. HT showed better in sparing of the organs at risk than RA except for the whole brain, mouth, parotid gland, small intestine and rectum. The MU and treatment delivery time of RA and HT were 2566 MU/568 s and 12293 MU/875 s respectively. The ＂,/-analysis passing rates for head-neck, chest-abdomen, pelvic parts were98.9%±l.9%, 98.4%±1.8%, 97.4%±2.1% for RA plans and 94.3%±1.5%, 96.5± 1.2%, 94.1%± 1.9% for HT plans. Conclusion The two methods of IMAT using RA and HT can both improve the quality of TMI and achieve the smoothing distribution of dose between the beams. And the delivery efficiency of RA is better than that of HT. Two IMAT techniques are promising and can be put into clinic implementation of TMI.