中文摘要：

目的探讨基于4DCT的自由呼吸状态下全乳正向调强放疗（IMRT）临床靶体积（CTV）位移及体积变化与计划靶体积（PTV）及危及器官（OAR）剂量学变化的相关性。方法选择行保乳术后接受4DCT模拟定位患者17例，以T0为参考时相制定全乳正向IMRT计划，并将Tn时相的IMRT计划复制到其余9个时相上。观察呼吸周期中呼吸运动导致的PTV与OAR剂量学变化。结果自由呼吸状态下全乳CTV位移矢量为（2．09±0．74）mm，变化率为（3．05±0．94）％。CTV变化与胛V及OAR剂量学变化无关（r=-0．390—0．480，P=0．182～0．775）；CTV在前后、头脚及矢量方向与PTV平均受量、适形指数、肺脏高剂量受照体积均相关（r=-0．975～0，791，P=0．000～0．041）；CTV头脚、矢量方向位移仅与心脏V5有关（r=-0．795、0．687，P=0．006、0．028）。肺体积变化与其高剂量受照体积呈正相关（V20、V30、V40、V50，r=0．655～0．882，P=0．001—0．040），而心脏体积变化仅与V，相关（r=-0．701，P=0．024）。结论自由呼吸状态下实施保乳术后全乳正向IMRT，乳腺固有体积变化对放疗影响可忽略，基于4DCT定位并制定治疗计划或辅助呼吸控制可保证全乳正向IMRT实施更为准确。

英文摘要：

Objective To explore the correlation between the respiration-induced clinical target volume （CTV） motion and volume variation and the dosimetric variation of planning target volume （PTV） and organs at risk （OAR） during free-breathing （ FB ） with whole breast intensity-modulated radiotherapy （IMRT）. Methods Seventeen patients with breast conserving surgery underwent respiration-synchronized four-dimentional computed tomography （4DCT） simulation scans on the State of FB. The treatment plan was constructed using the end-inspiration phase scan, then copied and applied to the other respiratory phases. The close distribution was calculated separately to evaluate the dose-volume histograms parameters for the PTV, ipsilateral lung and heart. Results During FB, the CTV motion vector was （2.09 ± 0. 74） mm, and the volume variation was （3.05 ±0. 94）%. There was no correlation between the volume variation of CTV and dosimetric variation of PTV/OAR （ r = -0. 390 -0. 480, P = 0. 182 -0. 775 ）. In anteroposterior （AP）, superoinferior （SI） and vector directions, the CTV movement correlated well with the PTV mean dose, conformal index, and the lung volume receiving high dose （V20, V30, V40, and Vs0;r = -0. 975 -0. 791,P = 0. 000 -0. 041 ）. In SI and vector directions, the CTV displacement only correlated with the heart volume receiving 〉 5 Gy （ V5 ） （ r = - 0. 795,0. 687, P = 0. 006,0. 028 ）. The lung volume variation and the lung volume receiving high dose correlated reasonably well （r = 0. 655 -0. 882, P= 0. 001 -0. 040）. The heart volume variation only correlated with the V5 of heart （ r = -0. 701, P = 0. 024 ）. Conclusions During free-breathing, the effect of breast volume variation can be ignored for whole breast IMRT, and whole breast IMRT assisted with breath-hold may improve the accuracy of dose delivery during radiotherapy.