摘要
Abstract
Objective To investigate the dosimetry effects of cone beam CT(CBCT)guided positioning error on the target area and organs at risk of intensity modulated radiation therapy(IMRT)in patients with lung cancer.Methods A total of 35 patients with lung cancer who underwent IMRT in Beijing Chest Hospital,Capital Medical University were selected as the study objects.And a total of 175 CBCT data were collected.The mean value of multiple positioning errors for each patient was calculated,and the mean value of positioning errors in X(left and right),Y(head and foot),and Z(lift and fall)directions were obtained.The mean value was reset to generate a simulated plan for the treatment center,and the obtained dosimetry data(including target areas and organs at risk)were compared with the original plan,to study the effect of positioning error on IMRT dose of lung cancer.Results The position-ing errors in X,Y and Z directions were(-0.17±2.67),(0.80±3.39)and(-0.13±2.23)mm,respectively.Among them,the ratio of Y orientation error greater than 5 mm accounted for the highest proportion,up to 17%.Comparing the original plan with the simulated plan,the prescribed dose percentages corresponding to D98%(minimum dose received by 98%of the target volume,and so on),D95%and D2%of the planning target volume were 98.66%±0.52%,100.29%±0.43%and 106.71%±0.71%,respectively.Compared with 89.84%±1.82%,96.50%±1.06%and 107.33%±0.74%in the simulated plan,the differences were statistically significant(P<0.001).In the organs at risk,the spinal cord D1 cc(the maximum dose of the organ receiving 1 cc volume irradiation)and Dmax(the maximum dose)increased from the original planned dose,respectively,with statistical significance(P<0.05);and comparing the rest of the heart[V30(percentage of the volume of organs receiving at least 30 Gy dose,and so on),V40,Dmean(average dose)],double lungs(V5,V20,Dmean),esophagus(V30,V50,Dmean),left anterior descending coronary artery and other organs at risk of the simulated plan target area metrological parameters with the original plan,there were no statistical significance(P>0.05).Conclusion CBCT can be used to measure the positioning error of IMRT in lung cancer.The positioning error can have dosimetry effect on the actual radiotherapy plan.In clinical practice,the error value measured by CBCT can be adjusted to reduce the positioning error and reduce the influence on the actual radiotherapy plan.关键词
调强放疗/锥形束CT/摆位误差/肺癌/放疗计划/剂量学Key words
intensity modulated radiation therapy(IMRT)/cone beam CT(CBCT)/positioning error/lung cancer/radiotherapy plan/dosimetry分类
预防医学
