CAJ | 학술논문

目的：应用千伏锥形束CT研究鼻咽癌调强放疗中的摆位误差，探讨其对靶区和危及器官剂量分布的影响。方法选取经确诊的鼻咽癌调强放疗患者15例，按热塑膜上三点标记摆位后每周行一次KV-CBCT扫描，重建后获取断层图像，使其与计划定位图像行匹配比较，得出该患者在三维方向及旋转的摆位误差。除摆位中心点外所有计划参数不变，在定位影像上模拟剂量分布并与最初治疗计划比较。结果在腹背、头脚、左右3个方向和水平面旋转的摆位误差均值分别为-1．83 mm、-0．32 mm、0．96 mm和-0．83°；GTVnx D95、GTVnd D95、CTV2 D95、PTV2 D95、PTVnd D95的剂量变化为-1．28％～-0．32％、-3．31％～-0．63％、-2．33％～-1．30％、-2．51％～-0．45％、-2．53％～-0．48％；脑干、脊髓、视交叉的Dmax变化范围分别为：-3．14％～12．58％、-22．91％～21．21％、-7．25％～14．77％。腮腺D50为-13．87％～18．21％，Dmean为-6．84％～9．21％。结论鼻咽癌调强放疗由于摆位误差等因素的存在，影响了靶区剂量分布，OAR（ organs at risk ）辐射剂量明显增高；应用KV-CBCT系统，可有效减少治疗误差，提高调强放疗精度。
목적：응용천복추형속CT연구비인암조강방료중적파위오차，탐토기대파구화위급기관제량분포적영향。방법선취경학진적비인암조강방료환자15례，안열소막상삼점표기파위후매주행일차KV-CBCT소묘，중건후획취단층도상，사기여계화정위도상행필배비교，득출해환자재삼유방향급선전적파위오차。제파위중심점외소유계화삼수불변，재정위영상상모의제량분포병여최초치료계화비교。결과재복배、두각、좌우3개방향화수평면선전적파위오차균치분별위-1．83 mm、-0．32 mm、0．96 mm화-0．83°；GTVnx D95、GTVnd D95、CTV2 D95、PTV2 D95、PTVnd D95적제량변화위-1．28％～-0．32％、-3．31％～-0．63％、-2．33％～-1．30％、-2．51％～-0．45％、-2．53％～-0．48％；뇌간、척수、시교차적Dmax변화범위분별위：-3．14％～12．58％、-22．91％～21．21％、-7．25％～14．77％。시선D50위-13．87％～18．21％，Dmean위-6．84％～9．21％。결론비인암조강방료유우파위오차등인소적존재，영향료파구제량분포，OAR（ organs at risk ）복사제량명현증고；응용KV-CBCT계통，가유효감소치료오차，제고조강방료정도。
Objective Objective To evaluate the set-up errors of intensity-modulated radiotherapy ( IMRT) in nasopha-ryngeal carcinoma ( NPC) and analyze its effects on dose distribution of targets and peripheral organs at risk ( OAR) using kilo-volt cone-beam CT ( KV-CBCT) .Methods 15 NPC patients who received IMRT were selected .They were set up by 3 points on thermoplastic film ,and scanned by KV-CBCT once a week .Sectional images were acquired after reconstruction and compared with the planning CT images ,the variations of three dimensional and horizontal rotation could be achieved .Transplanting the offset cen-tral point of three dimensional and horizontal rotation to the primary positioning images ,the other parameters were invariant .The dose distributions were simulated on the primary treatment planning CT images and the dose distributions betweem them were compared.Results The mean values of set-up errors on anteroposterior,craniocaudal,lateral position and rotation was -1.833 mm,-0.32 mm,0.96 mm,-0.8333 degree,respectively.The dose variations for GTVnxD95,GTVndD95,CTV2D95,PTV2D95,and PTVnd D95 were -1.28%~-0.32%,-3.31%~-0.63%,-2.33%~-1.30%,-2.51%~-0.45%,and -2.53%~-0.48%,respectively.Dmax of brainstem,spinal cord,and the optic chiasm were -3.14%~12.58%,-22.91%~21.21%,-7.25%~14.77%,respectively.The D50 and Dmean of parotid were -13.87%~18.21%and -6.84%~9.21%.Conclusion Due to the presences of set-up errors,dose distribution of nasopharyngeal carcinoma ( NPC) undergoing IMRT is affected ,and dose distribution of OAR increased significantly .KV-CBCT can reduce the treatment errors and improve the accuracy of IMRT .