Saw Cheng B, Chen Hungcheng, Beatty Ron E, Wagner Henry
Division of Radiation Oncology, Penn State Hershey Cancer Institute, Hershey, PA 17033-0850, USA.
Med Dosim. 2008 Summer;33(2):149-55. doi: 10.1016/j.meddos.2008.03.001. Epub 2008 Apr 1.
Image-guided radiation therapy (IGRT) relies on the quality of fused images to yield accurate and reproducible patient setup prior to dose delivery. The registration of 2 image datasets can be characterized as hardware-based or software-based image fusion. Hardware-based image fusion is performed by hybrid scanners that combine 2 distinct medical imaging modalities such as positron emission tomography (PET) and computed tomography (CT) into a single device. In hybrid scanners, the patient maintains the same position during both studies making the fusion of image data sets simple. However, it cannot perform temporal image registration where image datasets are acquired at different times. On the other hand, software-based image fusion technique can merge image datasets taken at different times or with different medical imaging modalities. Software-based image fusion can be performed either manually, using landmarks, or automatically. In the automatic image fusion method, the best fit is evaluated using mutual information coefficient. Manual image fusion is typically performed at dose planning and for patient setup prior to dose delivery for IGRT. The fusion of orthogonal live radiographic images taken prior to dose delivery to digitally reconstructed radiographs will be presented. Although manual image fusion has been routinely used, the use of fiducial markers has shortened the fusion time. Automated image fusion should be possible for IGRT because the image datasets are derived basically from the same imaging modality, resulting in further shortening the fusion time. The advantages and limitations of both hardware-based and software-based image fusion methodologies are discussed.
图像引导放射治疗（IGRT）依赖于融合图像的质量，以便在剂量输送前实现准确且可重复的患者摆位。两个图像数据集的配准可分为基于硬件或基于软件的图像融合。基于硬件的图像融合由混合扫描仪完成，这种扫描仪将两种不同的医学成像模态（如正电子发射断层扫描（PET）和计算机断层扫描（CT））整合到一个设备中。在混合扫描仪中，患者在两项检查期间保持相同位置，使得图像数据集的融合变得简单。然而，它无法进行在不同时间获取图像数据集的时间图像配准。另一方面，基于软件的图像融合技术可以合并在不同时间或使用不同医学成像模态获取的图像数据集。基于软件的图像融合可以手动进行，使用地标，也可以自动进行。在自动图像融合方法中，使用互信息系数评估最佳匹配。手动图像融合通常在剂量规划时以及IGRT剂量输送前进行患者摆位时执行。将展示在剂量输送前获取的正交实时射线照相图像与数字重建射线照相的融合。尽管手动图像融合已被常规使用，但使用基准标记缩短了融合时间。对于IGRT而言，自动图像融合应该是可行的，因为图像数据集基本上源自相同的成像模态，从而进一步缩短融合时间。本文讨论了基于硬件和基于软件的图像融合方法的优缺点。
