乳腺癌螺旋断层放射治疗与调强放射治疗的剂量学研究与临床剂量实测比较

摘要

目的:利用螺旋断层放射治疗技术与传统医用直线加速器对乳腺癌放疗中重要正常组织与靶区剂量-体积参数进行剂量学比较.同时,在剂量学研究基础上进行临床实际吸收剂量测量验证各种技术间临床应用的优势与劣势.方法:选取10例T1N0M0期乳腺癌保乳术后行乳腺靶区放射治疗病人(无锁骨上照射区域),处方剂量为50 Gy/25次,利用螺旋断层放射治疗定角调强技术、螺旋断层放疗技术与医用直线加速器调强技术,比较乳腺癌靶区剂量和正常组织剂量的优劣.评估靶区剂量与适形度指数(CI)、均匀性指数(HI)和正常组织剂量-体积参数,进行剂量学比较.同时,利用热释光剂量仪在乳腺癌病人表皮进行实测剂量,比较3种技术处理由于病人呼吸运动对表面剂量的影响,及评估时间因素对治疗效率的影响.结果:10例乳腺癌病人采用定角调强技术、螺旋断层放疗技术与医用直线加速器调强技术PTV HI分别为0.15±0.01、0.06± 0.01和0.20±0.15(P<0.001);CI分别为0.76±0.00、0.81±0.03和0.74±0.04(P>0.05);心脏平均剂量分别为4.12±0.87、3.82± 0.53、6.33±2.49 Gy(P<0.001),左前降支最大剂量分别为20.38±5.66、13.34±3.78、34.56±4.12 Gy(P<0.001),患侧肺组织平均剂量分别为6.78±1.33、7.22±2.34、12.76±2.10 Gy(P<0.001).患者6个实测剂量点的吸收剂量3种技术比较有统计学意义(P<0.001).结论:从综合靶区覆盖、正常组织剂量-体积参数、剂量实测与治疗效率等方面比较,螺旋断层放射治疗的定角调强技术相对于其他两种技术而言有低剂量范围小、靶区覆盖佳、解决治疗中呼吸运动影响等优势,推荐使用该技术用于乳腺癌病人放射治疗.%Objective To evaluate the dosimetry differences in dose-volume parameters of the breast and normal tissues in Tomotherapy and conventional Linac for breast cancer,and verify the advantages and disadvantages of various technologies by performing absorbed dose measurement based on dosimetry study. Methods Three radiotherapy treatment plans, namely TomoDirect intensity-modulated radiotherapy(IMRT),TomoHelical and IMRT,were designed for 10 patients receiving breast-conserving surgery for breast cancer(T1N0M0),with a prescribed dose of 50 Gy/25 F and without supraclavicular irradiation area. The dose of target areas and normal tissues,conformity index,homogeneity index,and dose-volume parameters of normal tissues were compared to evaluate the advantages and disadvantages of different technologies.Meanwhile,the dose of surface target was measured with thermoluminescent dosimeter for comparing the effects of respiratory motion on surface dose and assessing the effects of time factor on treatment efficiency.Results In TomoDirect IMRT,TomoHelical,IMRT plans for breast cancer in 10 patients,the homogeneity index of planning target volume was 0.15±0.01,0.06±0.01 and 0.20±0.15,respectively(P<0.001);conformity index was 0.76±0.00,0.81±0.03 and 0.74±0.04,respectively(P>0.05).For the organs-at-risk,the mean dose of the heart was(4.12±0.87),(3.82±0.53)and(6.33±2.49)Gy,respectively(P<0.001);the maximum dose of left anterior descending artery was(20.38±5.66),(13.34±3.78)and(34.56±4.12)Gy,respectively(P<0.001);and the mean dose of the ipsilateral lung was(6.78±1.33),(7.22±2.34)and(12.76±2.10)Gy,respectively(P<0.001).The absorbed dose at 6 measurement points also showed statistical significances(P<0.001).Conclusion Compared with the other two technologies,TomoDirect IMRT had the advantages of small low-dose region,better dose coverage and reducing the effects of respiration motion.TomoDirect IMRT is recommended for patients with breast cancer.