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目的探索心脏前壁区域(anterior myocardial territory,AMT)作为独立的危及器官在左乳腺癌保乳术后放疗中心脏保护的可行性。方法随机选取23例左乳癌接受保乳术后及术后辅助放疗的患者的计划CT图像。由同一个放疗医师勾画靶区和危及器官(OAR),OAR包括心脏(H)、AMT、左心室(left ventricle,LV)、左右肺和右侧乳腺。每个患者由物理师设计两个调强治疗计划(IMRT),一个是以AMT作为目标函数,另一个是以H+LV作为目标函数。所有治疗计划的处方剂量均为50Gy,25次。比较计划靶区(PTV)、AMT、LV、心脏、左右肺和右侧乳腺的剂量体积参数。结果 IMRT(AMT)和IMRT(H+LV)2个计划的PTV剂量的均匀指数、适形指数、覆盖指数均无明显差别。与IMRT(AMT)计划相比,IMRT(H+LV)中AMT的最大剂量明显增加,平均剂量增加有统计学意义,AMT的V12Gy、V13Gy、V15Gy、V17Gy和V20Gy分别增加15.37%、18.87%、26.48%、27.11%(P<0.05),LV的V5Gy、V7Gy、V8Gy和V10Gy分别增加4.21%、16.72%、20.91%和19.14%(P<0.05)。心脏和左肺的各个剂量体积参数无统计学差别,多数右肺和右乳腺的剂量体积参数无明显统计学差别。结论在左乳腺癌术后放疗中,AMT可作为替代心脏的一个独立危及器官可明显降低心脏照射剂量。
Objective To explore the feasibility of anterior myocardial territory (AMT) as an independent endangered organ in the central protection of left breast cancer after radiotherapy. Methods Twenty-three patients with left breast cancer undergoing breast-conserving surgery and postoperative adjuvant radiotherapy were enrolled in the study. Targets and organs at risk (OAR) are outlined by the same radiologist, including the heart (H), AMT, left ventricle (LV), left and right lungs, and right breast. Each patient was designed by physicists with two IMRTs, one with AMT as the objective function and the other with H + LV as the objective function. The prescription dose for all treatment plans was 50 Gy, 25 times. Dose volume parameters of the planned target volume (PTV), AMT, LV, heart, left and right lung, and right breast were compared. Results There was no significant difference in the average index, conformal index and coverage index of two PTV doses of IMRT (AMT) and IMRT (H + LV). Compared with the IMRT (AMT) program, the maximum dose of AMT in IMRT (H + LV) increased significantly and the average dose increased statistically. The V12Gy, V13Gy, V15Gy, V17Gy and V20Gy in AMT increased by 15.37% and 18.87% 26.48% and 27.11% respectively (P <0.05). V5Gy, V7Gy, V8Gy and V10Gy of LV increased by 4.21%, 16.72%, 20.91% and 19.14% respectively (P <0.05). No statistically significant differences were found in the dose-volume parameters between the heart and the left lung. There was no significant difference in dose-volume parameters between the right and left breasts. Conclusions In the postoperative radiotherapy of left breast cancer, AMT can be used as an independent organ to replace the heart can significantly reduce the dose of cardiac irradiation.