Impact Of Different Gating Techniques For Early Left Sided Breast Cancer With Intensity-modulated Radiotherapy After Breast-conserving Surgey

Respiratory movement deviation for tumor of breast cancer is one of the most important reasons that affected the accuracy of radiotherapy.4DCT can accurately describe the change of tumor motion and spatial position of the chest or abdominal cancer. Respiration gating technique is one kind of respiration control technology, it can record breath movement through monitor the mark block on the patient's chest or abdomen.This main ideas of this study are discuss the influence on the target of early breast cancer caused by breath movement and the influence on the early breast cancer radiotherapy plan caused by different gating techniques.Fifteen early left sided breast cancer with intensity-modulated radiotherapy after breast conserving patients were enrolled.By combine RPM respiration gating system and CT simulation machine, the free breath CT,deep inspiration breath holding CT,and free breath 4DCT were got.And then reconstruction them, CTFB, CTIn50%, CTIn75%, CTIn100%,CTMIP, CTDIBH CTEx50%,CTEx75%, were created. Outline the clinical target volume based on image CTFB, CTIn50%, CTIn75%, CTIn100%, CTEx50%,CTEx75%, CTMIP and CTDIBH respectively, the CTVFB, CTVIn50, CTVIn75,CTVIn100, CTVEx50, CTVEx75, CTVMIP and CTVDIBH were got. Registration CTVIn50, CTVIn75, CTVIn100, CTVEx50, CTVEx75 on the CTIn75% generated CTVSum.Margin CTVFB, CTVSum and CTVDIBH 5mm respectively, got the PTVFB, PTVRG and PTVDIBH. Compare the volume of CTVFB.CTVIn50,CTVIn75, CTVIn100, CTVEx50, CTVEx75, CTVMIP, CTVSum and CTVDIBH.Outline the organs of risk(OARs): heart, lung-L, breast-R, lung-R on CTFB, CTIn75% and CTDIBH. Make intensity modulated radiotherapy plan based on the three groups of images genered three plans: Plan FB, Plan RG and Plan DIBH. Compare the D2%, D98%, Dmean.Conformity Index(CI) and Heterogeneity Index(HI) of three PTVs, MU and the dose of OAR.The results of this study are as follows: There were no statistically significant difference between the volume of CTVFB and CTVIn50,CTVIn75, CTVIn100, CTVEx50, CTVEx75, But the significant difference were found when compare the volume of CTVFB and CTVMIP, CTVSum, the values of P were 0.001 and 0.003 respectively. Meanwhile, there was also statistically significant difference between the volume of CTVSum and CTVIn50,CTVIn75,CTVIn100,CTVEx50,CTVEx75,CTVMIP the values of P were0.003,0.002,0.005,0.004,0.000,0.001respectively;When compare the three radiotherapy treatment plans of PTV parameters:D2%,D98%,Dmean,the difference were not obvious. But the values of D2% were diminished in the order of FB, RG, DIBH, while the values of D98% were increased in same order.The difference of the CI, HI, MU were small. The significant difference were found when compare the heart of V10, V20, V25, V30 and Dmean. To the dose parameter of lung volume, the left lung volume results were similar to the right lung. There were no significant difference in all the indexes for right breast and for the rest of left lung and right lung dose parameters.The results show that the motion of target caused by patients' respiratory should not be neglected.The dose that target received may not enough or have nothing, Sketch the target based on 4DCT is more accurate and reliable.Respiratory gating techniques can reduce the dose of heart and not increasing the dose of other OARs. For early left side conserving radiotherapy patient, DIBH respiratory gating technique is recommended.