Gao Song, Zhang Lifei, Wang He, de Crevoisier Renaud, Kuban Deborah D, Mohan Radhe, Dong Lei
Department of Radiation Physics, Unit 94, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030, USA.
Med Phys. 2006 Sep;33(9):3304-12. doi: 10.1118/1.2222077.
In image-guided adaptive radiotherapy, it is important to have the capability to automatically and accurately delineate the rectal wall, which is a major dose-limiting organ in prostate cancer radiotherapy. As image registration is a process to find the spatial correspondence between two images, a major challenge in intensity-based deformable image registration is to deal with the situation where no correspondence exists for some objects between the two images to be registered. One example is the variation of rectal contents due to the presence and absence of bowel gas. The intensity-based deformable image registration methods alone cannot create the correct spatial transformation if there is no correspondence between the source and target images. In this study we implemented an automatic image intensity modification procedure to create artificial gas pockets in the planning computed tomography (CT) images. A diffusion-based deformable image registration algorithm was developed to use an adaptive smoothing algorithm to better handle large organ deformations. The process was tested in 15 prostate cancer cases and 30 daily CT images containing the largest distended rectums. The manually delineated rectums agreed well with the autodelineated rectums when using the image-intensity modification procedure.
在图像引导的自适应放射治疗中，具备自动且准确地勾勒直肠壁的能力非常重要，直肠壁是前列腺癌放射治疗中的主要剂量限制器官。由于图像配准是寻找两幅图像之间空间对应关系的过程，基于强度的可变形图像配准中的一个主要挑战是处理待配准的两幅图像之间某些物体不存在对应关系的情况。一个例子是由于肠内气体的有无导致直肠内容物的变化。如果源图像和目标图像之间不存在对应关系，仅基于强度的可变形图像配准方法无法创建正确的空间变换。在本研究中，我们实施了一种自动图像强度修改程序，以在计划计算机断层扫描（CT）图像中创建人工气腔。开发了一种基于扩散的可变形图像配准算法，以使用自适应平滑算法更好地处理大器官变形。该过程在15例前列腺癌病例和30张包含最大扩张直肠的每日CT图像中进行了测试。使用图像强度修改程序时，手动勾勒的直肠与自动勾勒的直肠吻合良好。
