TomoDirect技术在全脑全脊髓放疗中的应用

目的 为全脑全脊髓放疗建立新的TomoDirect技术(TD)布野方案,并评价剂量学参数。方法 对本院收治的7例全脑全脊髓放疗患者进行回顾性研究,在Tomo计划系统分别设计5野TD、3野TD和螺旋断层治疗(helical tomotherapy, HT)计划,比较3种计划的靶区适形指数(CI)、均匀性指数(HI)、危及器官受量、治疗时间和机器跳数(MU)。结果 除3野TD计划外其余两者均能获得较好的靶区适形度和均匀性。其中5野TD计划靶区受量明显优于3野TD计划,但略逊于HT计划;危及器官受量则各有优势。5野TD、3野TD和HT计划的靶区平均CI分别为0.79、0.57和0.88;靶区HI分别为1.06、1.16和1.05;双肺V₂₀分别为1.99%、3.30%和2.16%;心脏平均剂量分别为6.17、12.38和10.72 Gy;肝脏平均剂量分别为5.21、5.14和4.62 Gy;左侧肾脏平均剂量分别为4.30、1.99和5.03 Gy;右侧肾脏平均剂量分别为4.42、2.09和4.91 Gy。靶区以外的正常组织V₅分别为46.80%、28.06%和55.54%。5野TD计划的治疗时间最短,5野TD、3野TD及HT计划的平均治疗时间分别为677、721和907 s,MU数分别是8 773、9 657和12 581。结论 5野的TD技术应用于全脑全脊髓放疗具有一定优势,适用于难以坚持长时间治疗,且希望减少低剂量范围的患者。

Application of TomoDirect for craniospinal irradiation

Objective To establish a new approach of beam arrangement with TomoDirect(TD) for craniospinal irradiation and evaluate the plan quality and treatment time. Methods Totally 7 patients were chosen for craniospinal irradiation planning in tomotherapy planning system. The 5-field TomoDirect plans, the 3-field TD plans and the Helical Tomotherapy (HT) plan were designed for each patient, respectively. Conformal index(CI), homogeneity index(HI)for PTV, dose parameters for OARs and mean dose of normal tissue were compared between these of two groups. The treatment time and monitor units were also compared. Results Except for the 3-field TD plans, all plans were able to achieve good dose conformity and dose homogeneity. The 5-field plan was superior to the 3-field plan, but a little inferior to the HT plan for the target dose. And all plans had their respective advantages for the dose of OARs. For the 5-field TD plan, the 3-field TD plan and the HT plan, the mean CI and HI were 0.79, 0.57, 0.88 and 1.06, 1.16, 1.05, respectively. The V₂₀ of lung were 1.99%, 3.30%, 2.16%, respectively. The mean dose of heart was 6.17, 12.38 and 10.72 Gy, respectively. The mean doses of liver were 5.21, 5.14 and 4.62 Gy, respectively. The mean doses of left kidney were 4.30, 1.99 and 5.03 Gy, respectively. The mean doses of right kidney were 4.42, 2.09 and 4.91 Gy, respectively. The V₅ of NT was 46.80%, 28.06% and 55.54%, respectively. The treatment time of the 5-field TD plan was the shortest one comparing with the other plans. The mean treatment time was 677, 721, and 907 s for the 5-field TD plan, the 3-field TD plan and the HT plan, respectivley. The number of MUs was 8 773, 9 657 and 12 581 for each plan. Conclusions The 5-field TD plan can decrease low dose volume in normal tissues outside the PTV and has shorter treatment time. It can be recommended for the patients like children who cannot tolerate long treatment time and need avoiding low dose to a large volume.