TomoDirect和TomoHelical技术在左侧乳腺癌保乳术后放疗中的剂量学比较

Dosimetric comparison of TomoDirect and TomoHelical modalities in Tomotherapy system for leftbreast cancer radiotherapy after breast-conserving surgery

目的比较4野和6野断层定野照射（TomoDirect）及断层螺旋照射（TomoHelical）技术在左侧乳腺癌保乳术后患者的放疗计划应用中的剂量学差异。方法作为回顾性研究，本文选取16例已行调强（IMRT）治疗的左侧乳腺癌保乳术后患者，在螺旋断层放疗（Tomotherapy）计划系统上分别进行4野和6野的TomoDirect及TomoHelical3种技术的模拟计划，比较3种技术设计的计划靶区和危及器官的剂量学差异及治疗参数。结果3种技术设计的乳腺癌计划，均能满足临床要求。其中，4野TomoDirect技术对危及器官和正常组织，尤其是脊髓、健侧乳腺最大剂量Dmax，肺的V5，心脏Dmean（F=595．60、129．24、60．44、65．37，P〈0．05）的保护优于TomoHelical技术，但在靶区剂量均匀性和适形度方面，以TomoHelical技术较优（F=2．78、60．93，P〈0．05）。6野TomoDirect技术，在保证较TomoHelical技术低的危及器官限量的条件下，提高了4野TomoDirect技术的靶区均匀性和适形度。此外，TomoDirect技术的机器跳数均优于TomoHelical技术，有效地减少了患者治疗时间（F=24．89、3．75，P〈0．05）。结论对于左侧乳腺癌保乳术后放疗，6野TomoDirect技术设计的计划具有一定优势，与TomoHelical技术相比，6野TomoDirect大大降低了危及器官受量；与4野TomoDirect技术相比，6野TomoDirect靶区均匀性和适形度较优，更适宜于早期乳腺癌患者。

Objective To compare the dosimetric difference among plans designed by 4-field, 6- field TomoDirect and TomoHelical techniques in Tomotherapy system for left-breast cancer patients with radiotherapy after breast-conserving surgery. Method A total of 16 patients with left-breast cancer following breast-conserving surgery and intensity-modulated radiation therapy were enrolled in this retrospective study. The 4-field TomoDireet （ TD4 ） , 6-field TomoDirect （ TD6 ） , and TomoHelical （TH） techniques were applied to design simulation plans in tomotherapy system for each patient, respectively. The differences of dose distribution and treatment parameters were analyzed in this study. Results Three plans all met the clinical requirement. Thereinto, TD4 was superior to TH in the dose limitation of organs at risk （OARs） , especially the max dose of cord and right-breast, the 5 Gy radiation volume of lung, and the mean dose of heart（F = 595.60, 129.24, 60.44, 65.37, P 〈 0.05）, but inferior to TH in dose homogeneity （HI） and conformity （CI） （ F = 2.78, 60. 93, P 〈 0.05 ）. However, TD6 improved TD4,s HI and CI when delivered the lower OARs dose compared to TH. Meanwhile, the number of monitor units was less in TD technique and reduced the treatment times （ F = 24.89, 3.75, P 〈 0.05 ）. Conclusions For the radiotherapy of left-breast cancer patients after breast-conserving surgery, TD6 technique appeared to be superior, with the lower radiation dose of OARs compared to TH technique, and the better target＇s HI and CI in comparison with TD4 technique, especially in patients with early stage breast cancer.