应用4DCT研究乳腺癌根治术后胸壁IMRT的放射物理学优势

The radiation physics advantages of 4DCT on intensity-modulated radiotherapy of chest wall after radical mastectomy

目的 探讨根治术后乳腺癌胸壁IMRT时为克服呼吸运动影响应用4DCT确定靶区的临床价值.方法 对入组的17例乳腺癌根治术后患者序贯进行常规CT和4DCT扫描并采集图像,分别勾画靶区和正常组织.根据每位患者的3D、4D靶区分别制定3D计划和4D计划,并将3D计划按等中心坐标直接复制到4D靶区上比较差异及OAR剂量学变化,并行配对t检验或Wilcoxon符号秩检验.结果 自由呼吸状态下呼吸运动导致PTV4D较PTV3D.平均增大（10.35±4.80）％（P=0.000）,V100、V95、V90、D95、D90、Dmin分别降低（0.78 ～ 18.0）％（P=0.000）、（0.01～3.90）％（P=0.000）、（0～2.12）％ （P =0.000）、（13～222） cGy （P=0.000）、（1～118） cGy （P=0.000）、（6～1 910） cGy （P=0.000）.而呼吸运动对患侧肺V20、V10、V5、Dmean和心脏V30影响不明显（P =0.288、0.407、0.435、0.758、0.575）.结论 呼吸运动可能降低3D靶区剂量及覆盖范围,4DCT个体化放疗计划在保证胸壁靶区照射精度的同时并不增加正常组织受量.

Objective To invesigate the influence of breathing motion on intensity-modulated radiotherapy （IMRT） of chest wall after radical mastectomy, and explore clinical value of accurately determined target volume. Methods A total of 17 radical mastectomy patients underwent 3DCT simulation scans sequentially followed by 4DCT simulation scans during free breathing. The targets and normal organs was determined based on CT images respectively. Three sets of radiotherapy plan were designed for each patient：plan 3D, plan 4D and plan 3D-A. The Plan 3D and plan 4D was designed based on 3D and 4D targets respectively. Plan 3D was copied to 4D target with the same isoeenter coordinates. The dose distribution was calculated separately to evaluate the dose-volume histograms parameters for PTV, ipsilateral lung and heart, respectively. Two planning parameters was compared with paired t-test or Wilcoxon sign-rank test. Results The average volume of PTV4D was （ 10.35± 4. 80 ） % larger than PTV3D （ P = 0. 000 ）. Compared with plan 3D, the V100 , V95,V90, D95 , Dg0, Drain of plan 3D-A were reduced, that were （0.78 --18.0）%（P=0.000）, （0.01 --3.90）% （P=0.000）, （0 --2. 12）% （P=0.000）, （13--222） eGy （P=0.000）,（1--118） cGy （P=0.000）,（6--1 910） cGy （P=0.000）. However, the V20, V10, V5, D of the ipsilateral lung and V30 of heart were same between 3D plan and 4D plan （P = 0. 288,0. 407, 0. 435,0. 758,0. 575）. Conclusions The respiratory motion may reduce the target dose and its coverage in chest wall treatments, so 4DCT plan could accurately define target volume without increasing the exposure dose of normal tissues.