Abstract：Objective To analyze the effect of positioning error on radiotherapy planning dose after breast conserving surgery for
breast cancer. Methods A total of 15 female patients with left and right breasts conserving surgery were selected as the study objects,
respectively. By moving the treatment center of the treatment plan to simulate the positioning errors, the effect of different positioning
errors on D95 of clinical target volume (CTV-D95), D95 of CTV-boost (CTV-boost-D95) was analyzed, as well as the effects on organs
at risk (lung V5, lung V20, Dmean in the health-side breast, Dmean in the heart of left breast patients. Results When the set-up error
was in the one direction within 0.5 cm, the CTV-D95 was close to the original plan, and the dose of organs at risk was significantly
reduced in the direction of the treatment center bias to the affected side breast, head, and abdomen. The average of CTV-D95 was
significantly reduced, and the dose of organs at risk was significantly increased in the treatment center bias to the healthy side breast,
foot, back. Among them, the dose variation in the treatment center was the largest in the back direction, but all of them were in the
clinically acceptable range. The planned dose effect was also acceptable when the treatment center was simultaneously bias to the
affected side breast, head, and abdomen within 0.5 cm or simultaneously bias to the healthy side breast, foot, back within 0.3 cm.
When the treatment center was simultaneously bias to the healthy side breast, foot, back reaches 0.5 cm, CTV-D95，CTV-boost-D95
were less than 95% of the prescription dose, and the average value of V20 in the lung had exceeded the dose limit, and the actual dose
did not meet the clinical requirements. Conclusion When the average set-up error of this radiotherapy center is less than 0.3 cm in
the direction of the X, Y, and Z, the dose effect caused by the set-up error is basically in the scope of clinical acceptance. It should be
attracted great attention to the therapist when the treatment center is simultaneously bias to the healthy side breast, foot, back reaches
0.5 cm, and the number of CBCT can be appropriately increased.
钟思瑶，孙斌，徐程，李海亮，高玉艳. 乳腺癌保乳术后摆位误差对放疗
计划剂量的影响[J]. 中国医疗设备, 2024, 39(1): 67-72.
ZHONG Siyao, SUN Bin, XU Cheng, LI Hailiang, GAO Yuyan. Effect of Positioning Error on Radiotherapy Planning Dose After Breast Conserving Surgery. China Medical Devices, 2024, 39(1): 67-72.
