ABAS软件勾画OAR临床前测试重要性研究

Commissioning of an atlas-based auto-segmentation software for application in organ contouring of radiotherapy planning

目的 对基于模板自动分区（ABAS）算法的图像勾画软件进行临床前测试,评估鼻咽癌放疗计划OAR勾画精度,为确定临床应用条件提供依据。方法 以放疗医师在22例鼻咽癌患者放疗计划CT图像上手工勾画的OAR结构为评价标准,分别对ABAS软件两种算法（General和Head/Neck）自动勾画的OAR进行以下测试：（1）每1例患者均拷贝1套图像,以原图像上手工勾画的轮廓为模板在拷贝图像上自动勾画,考察自动勾画对模板的还原能力;（2）以1例患者图像上手工勾画的轮廓为模板,对其余患者图像进行自动勾画,考察采用单一模板对不同患者图像自动勾画的准确度。评价指标包括各OAR的DSC、Vdiff、DSC与勾画体积相关性,以及自动勾画加手工修改与单纯手工勾画的耗时差别。Wilcoxon符号秩检验,Spearman相关性分析。结果 Head/Neck算法对模板还原能力优于或相当于General算法,自动勾画DSC与所勾画结构体积大小呈正相关（rs=0.879、0.939）。还原测试中体积〉1 cm3器官自动勾画的DSC〉0.8。使用Head/Neck算法基于单一模板的自动勾画中,脑干、颞叶、腮腺、下颌骨的DSC和Vdiff平均值分别为0.81~0.90和2.73%~16.02%,颞颌关节和视交叉DSC为0.45~0.49。应用自动勾画加手工修改比单纯手工勾画可以节省68%时间。结论 临床前测试可以确定ABAS算法在特定临床应用条件的准确度和适用范围,所测试软件可帮助提高鼻咽癌放疗计划OAR勾画效率,但不适用于较小体积器官的勾画。

Objective To perform a preclinical test of a delineation software based on atlas-based auto-segmentation （ABAS）, to evaluate its accuracy in the delineation of organs at risk （OARs） in radiotherapy planning for nasopharyngeal carcinoma （NPC）, and to provide a basis for its clinical application. Methods Using OARs manually contoured by physicians on planning-CT images of 22 patients with NPC as the standard, the automatic delineation using two different algorithms （general and head/neck） of the ABAS software were applied to the following tests：（1） to evaluate the restoration of the atlas by the software, automatic delineation was performed on copied images from each patient using the contours of OARs manually delineated on the original images as atlases;（2） to evaluate the accuracy of automatic delineation on images from various patients using a single atlas, the contours manually delineated on images from one patients were used as atlases for automatic delineation of OARs on images from other patients. Dice similarity coefficient （DSC）, volume difference （Vdiff）, correlation between the DSC and the volume of OARs, and efficiency difference between manual delineation and automatic delineation plus manual modification were used as indices for evaluation. Wilcoxon signed rank test and Spearman correlation analysis were used. Results The head/neck algorithm had superior restoration of the atlas over the general algorithm. The DSC was positively correlated with the volume of OARs and was higher than 0.8 for OARs larger than 1 cc in volume in the restoration test. For automatic delineation with the head/neck algorithm using a single atlas, the mean DSC and Vdiff were 0.81-0.90 and 2.73%-16.02%, respectively, for the brain stem, temporal lobes, parotids, and mandible, while the mean DSC was 0.45-0.49 for the temporomandibular joint and optic chiasm. Compared with manual delineation, automatic delineation plus manual modification saved 68% of the time. Conclusions A preclinical test is able to determine the accuracy and conditions of the ABAS software in specific clinical application. The tested software can help to improve the efficiency of OAR delineation in radiotherapy planning for NPC. However, it is not suitable for delineation of OAR with a relatively small volume.