放疗射野影像验证中CR不同摄影剂量对图像显示效果的影响(ROC曲线分析)

Effects of Different CR Exposure Dose on Image Quality in Radiotherapy Field Verification (ROC Curve Analysis)

目的:评价CR不同摄影剂量在放疗射野影像验证中的图像显示效果。方法:将98颗直径为6mm的塑料小球作为信号源置于仿人体头颅模型上,以6MV的能量分别在1~8MU的剂量下由CR成像板获取信息并打印出照片,由3位放射学医师用5等级判别法各自独立阅片,用Rockit软件对观察结果进行ROC曲线分析。结果:1、2、3、4、5、6、7和8MU之Az值分别为0.7672、0.8253、0.8723、0.8832、0.8856、0.8604、0.8148和0.6869,以摄影剂量为5MU的Az值最高。将其与其它摄影剂量的Az值做两两比较t检验发现,与1MU和8MU比较,其P值分别为0.0013和0.0042,均小于0.01,说明差异有显著性意义;其与2、3、4、6和7MU比较,其P值分别为0.2537、0.3328、0.4536、0.3736、0.1894,均大于0.05,说明差异均无显著性意义。结论:CR用于放疗射野影像验证的摄影剂量为2~7MU较为适宜。

Objective： To evaluate the effect on images in field verification in radiotherapy with different exposure dose. Method：98 plastic balls （diameter=6mm） were placed on the human head skull model as signal resource,and signals were obtained from CR Imaging plate with 6MV X-ray and different close vary from I^8MU. Images were read by three radiologists respectively according to five-rank judgments method,the results were taken ROC analysis with Rockit software. Results：Respective Az value of 1MU,2MU,3MU…8MU was 0, 7672.0. 8253.0. 8723.0. 8832.0. 8856.0. 8604,0. 8148, 0. 6869,The Az value of the 5MU was the highest,t-test between 5MU and others showed：P value of the 5MLT and 1MU was 0. 0013〈0.01,P value of the 5MU and 8MU was 0. 0042〈0.01, there was significant difference; the other P value was 0. 2537 （2MU）,0. 3328 （3MU）,0. 4536 （4MU）,0. 3736 （6MU）,0. 1894 （7MU）,all of P value〉0.05,there was no significant difference. Conclusion：2-7MU of CR exposure close in field verification in radiotherapy is suitable.