摆位误差对乳腺癌术后放疗患者心脏剂量影响

Effect of Set-up Error on Cardiac Dose in Postoperative Radiotherapy Patients with Breast Cancer

目的研究模拟摆位误差对左侧乳腺癌患者术后放疗心脏受照剂量的影响。方法选取17例左侧乳腺癌根治术后进行调强放疗的患者为研究对象。在计划系统中,模拟靶区中心相对于计划射野中心的偏移,包括向颅(S)、尾(I)、左(L)、右(R)、前(A)和后(P)各移动5 mm,并评估心脏受照剂量,分析不同方向的摆位误差对心脏剂量的影响。结果原始计划心脏平均剂量(Dmean)为5.72 Gy。射野中心向6个不同方向移动5 mm后,L、A、S方向心脏受照剂量减少,R、P、I方向心脏受照剂量增加,P方向心脏Dmean增加(1.46±0.24)Gy,R方向心脏Dmean增加(1.14±0.17)Gy,I方向心脏Dmean增加(0.43±0.25)Gy。结论左侧乳腺癌改良根治术后放疗,向R、P、I方向的摆位误差可增加心脏受照剂量,向L、A、S方向的摆位误差可减少心脏受照剂量。

Objective To investigate the effect of simulated set-up error on cardiac irradiation dose of left breast cancer patients after postoperative radiotherapy.Methods A total of 17 left breast cancer patients undergone modified radical mastectomy were enrolled as research object.In the planning system,the deviation of the center of the target volume relative to the center of the planned field was simulated,including moving 5 mm each towards the superior(S),inferior(I),left(L),right(R),anterior(A),and posterior(P).The cardiac irradiation dose was then assessed,with an analysis focusing on the influence of these set-up errors on cardiac dose.Results The mean cardiac irradiation dose(Dmean)of the original plan was 5.72 Gy.After the isocenter of irradiation beam were moved with 5 mm in six different directions,the cardiac irradiation dose decreased at the L,A,and S directions,while the cardiac irradiation dose increased at the R,P,and I directions.The cardiac irradiation dose Dmean increased by(1.46±0.24)Gy at the P direction,(1.14±0.17)Gy at the R direction,and(0.43±0.25)Gy at the I direction.Conclusion Set-up errors in the R,P,I directions during radiotherapy after modified radical mastectomy for left breast cancer can result in an elevated dose of cardiac irradiation.Set-up errors in the L,A,S directions can decrease the cardiac irradiation dose.