胰腺癌放疗图像引导锥束CT运动伪影修正技术研究

基于二维平板探测器技术的锥束CT系统广泛应用于放射治疗前的摆位验证，但在以胰腺癌为代表的腹腔肿瘤放疗应用中会遇到呼吸运动和肠道蠕动导致的严重阴影与条状伪影问题，难以从CT影像中分辨病灶区域。由于胰腺等柔性脏器在呼吸运动作用下会存在非刚性形变，体表运动监测结果和实际脏器运动间存在难以量化的偏差，也难以监测以肠道蠕动为代表的不规则运动，故腹腔锥束CT运动伪影修正问题缺乏有效解决方案。本文基于生物动力学理论和人体生理学常识，提出全新的无需运动监测或体内标记物植入的放疗图像引导锥束CT运动伪影修正方法，设计基于伪影图像特征、融合各类CT图像域处理算法的伪影修正策略。将该策略应用于临床腹腔锥束CT影像处理后所得结果表明锥束CT图像质量有显著改善，典型软组织区域的平均CT数误差从90 HU降到30 HU，肠道空腔边界和周边软组织信息得到部分恢复。本文开发的伪影修正策略无需呼吸门控或增加投影数，避免标记物植入手术，可集成到现有工作流，为胰腺癌放疗图像引导提供肿瘤定位信息。 

Development of Motion Artifact Correction Solutions for the Cone-beam CT Images during Pancreatic Cancer Image-guided Radiotherapy

The cone-beam CT (CBCT) system based on the two-dimensional flat-panel detector technology is widely applied in patient location verification before radiotherapy. However, during the application of intraperitoneal tumor radiotherapy, severe shading and streaking artifacts caused by respiratory movement and intestinal peristalsis make it difficult to distinguish tumor areas from the CBCT images. Due to the non-rigid deformation of flexible organs such as the pancreas under the action of respiratory motion, it is hard to quantify deviation between the body surface motion monitoring results and the actual organ motion, and it is also difficult to monitor irregular motion represented by intestinal peristalsis. There is no effective solution to motion artifact correction in CBCT. Based on theory of biodynamics and common knowledge of human physiology, in this paper we propose a brand new radiotherapy image-guided cone-beam CT motion artifact correction method without motion monitoring or implantation of in-vivo markers. The proposed artifact correction strategy is designed based on the features of the artifact images and fusion of various CT image domain processing algorithms. The results suggest that the image quality of cone beam CT has been significantly improved after the application of this strategy in the clinical abdominal CBCT image processing. The average CT number error in typical soft tissue areas reduces from 90 HU to 30 HU, and the boundary of the intestinal cavity and surrounding soft tissue information are partially recovered. The proposed artifact correction strategy does not require respiratory gating or increase of projections, which can be integrated into existing workflows without marker implantation surgery. The motion-artifact-corrected CBCT images provide more accurate tumor localization information for image-guided radiotherapy of pancreatic carcinoma. The proposed method is proved practical and efficient for clinical applications