兆伏级锥形束CT图像下鼻咽癌调强放疗计划的优化研究

目的 探讨兆伏级锥形束CT(MVCBCT)图像下鼻咽癌患者调强放疗(IMRT)计划的优化方法.方法 利用XiO治疗计划系统模拟MVCBCT图像采集过程.计算3例鼻咽癌患者不同MVCBCT扫描条件下[27.4 cm ×27.4 cm视野下8、5 MU(A、C),27.4 cm×15.0 cm视野下8、5 MU(B、D)]靶区(GTV、CTV)和危及器官或组织的平均剂量(DMVCBCT).依据IMRT常规计划和DMVCBCT求出剂量修正因子(CFMVCBCT),将CFMVCBCT附加MVCBCT成像过程重新对治疗计划进行优化.对DMVCBCT的A∶B、C∶D、A∶C、B∶D行配对t检验.结果 对于DMVCBCT和CFMVCBCT,GTV的A、B、C、D分别为7.78、5.78、4.88、3.55 CGy(A∶C不同,t=24.41,P＜0.01)和0.993～0.997,CTV1的分别为7.88、6.95、4.88、4.38 cGy(A∶B、A∶C、B∶C不同,t=3.85、-31.82、～8.52,P均＜0.01)和0.992～0.996,CTV2的分别为8.28、6.67、5.17、4.17 cGy(4个比较均不同,t=6.41～18.24,P均＜0.01)和0.991～0.996;脊髓的分别为6.88、5.00、4.28、3.50 cGy(A∶B、A∶C不同,t=2.83、11.03,P均＜0.05)和0.989～0.995,左腮腺的分别为7.88、7.38、4.95、4.62 cGy和0.984～0.990,左视神经的分别为8.67、0.28、5.33、0.28 cGy和0.963～0.999,左眼晶体的分别为9.17、0.22、5.72、0.17 cGy和0.821～0.997,脑干的分别为6.95、2.17、4.38、1.38 cGy和0.987～0.997,视交叉的分别为7.78、0.45、4.95、0.28 cGy和0.978～0.999(5个的4个比较均不同,t=5.06～335.16,P均＜0.01).结论 MVCBCT图像引导鼻咽癌患者IMRT过程将导致患者接受一定辐射剂量,通过对IMRT常规计划修正可消除其影响.

Optimization of the IMRT treatment plan undergoing megavoltage cone-beam CT Imaging for nasopharyngeal carcinoma patients

Objective To investigate the intensity modulated radiation therapy (IMRT) planning optimization method to reduce the additional dose resulting from megavoltage cone-beam CT (MVCBCT) imaging for nasopharyngeal carcinoma IMRT treatment. Methods MVCBCT images collection process was simulated using XiO treatment planning system. The mean doses of MVCBCT ( DMVCBCT ) were calculated in gross tumor volume ( GTV), clinical target volume ( CTV ) and risk at organ or tissue using 27. 4 cm× 27.4 cm portal radiation 8 MU,5 MU (A,C) and 27.4 cm× 15.0 cm portal radiation 8 MU,5 MU (B,D). The dose correct factor of MVCBCT (CFMVCBCT) according to IMRT TPS and DMVCBCT ,but CFMVCBCT plus MVCBCT imaging process for radiotherapy planning optimization. The paired t-test was play for A∶ B,C∶ D,A∶ C,B∶ D of DMVCBCT. Results The DMVCBCT and CFMVCBCT of A, B, C, D were 7. 78,5. 78,4. 88,3.55 cGy ( A∶ C, t =24.41,P＜0.01) and 0.993 -0.997 in GTV,with 7.88,6.95,4.88,4.38 cGy (A∶ B,A∶ C,B∶ C,t=3. 85, -31.82, -8.52, all P＜0. 01) and 0.992 -0.996 in CTV1 ,with 8.28,6.67,5. 17,4. 17 cGy (A ∶B,A∶C,B∶C,B∶D,t=6.41 -18.24,all P＜0. 01) and 0.991 -0.996 in CTV2;with 6.88,5.00,4.28,3. 50 cGy ( A∶ B, A∶ C,t = 2. 83,11.03, all P ＜ 0. 05 ) and 0. 989 - 0. 995 in spinal cord, with 7.88,7. 38,4. 95,4. 62 cGy and 0. 984 -0. 990 in left parotid, with 8. 67,0. 28,5. 33,0. 28 cGy and 0. 963 -0. 999 in left optic nerve,with 9. 17,0.22,5.72,0. 17 cGy and 0.821 -0.997 in left eye lens,with 6.95,2. 17,4. 38,1.38 cGy and 0. 987 -0. 997 in brain stem, with 7.78,0.45,4. 95,0. 28 cGy and 0. 978 -0. 999 ( A ∶ B,A∶ C,B∶ C,B∶ D for five organ or tissue,t =5. 06 -335. 16 ,all P ＜0. 01 ) in optic chiasm. Conclusions The MVCBCT imaging process resulted in radiation doses to patient. The impact of MVCBCT image acquired dose on IMRT treatment plan for NPC was eliminated by a compensation method.