Patch-based generation of a pseudo CT from conventional MRI sequences for MRI-only radiotherapy of the brain
Patch-based generation of a pseudo CT from conventional MRI sequences for MRI-only radiotherapy of the brain
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DOI：
10.1118/1.4914158
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发表时间：
2015-04-01
期刊：
影响因子：
3.8
通讯作者：
Edmund, Jens M.
中科院分区：
文献类型：
--
作者：
Andreasen, Daniel;Van Leemput, Koen;Edmund, Jens M.
目的：在基于磁共振成像（MRI）作为唯一模态的放射治疗（RT）中，必须通过创建所谓的伪计算机断层扫描（pCT）从MRI扫描中导出关于电子密度的信息。这是一项重要的任务，因为MRI扫描中的体素强度与电子密度并不唯一相关。为了解决该任务，通常使用基于体素或基于图谱的模型。基于体素的模型需要专门的双超短回波时间MRI序列用于骨可视化，基于图谱的模型需要常规MRI扫描的可变形配准。在这项研究中，我们研究了一种基于补丁的方法，用于在不使用变形配准的情况下基于传统的T-1加权MRI扫描创建pCT。我们比较这种方法对两个国家的最先进的方法内的体素为基础的和atlas-based categorization.Methods：数据包括5个头颅RT患者的CT和MRI扫描。为了比较不同方法的性能，进行嵌套交叉验证以找到所有方法的最佳模型参数。进行了pCT的体素和几何评价。此外，进行了基于水等效路径长度的放射学评价，比较了pCT和真实的CT中的头部上半球。最后，剂量测定的准确性进行了测试和比较的光子治疗plannes.Results：与补丁为基础的方法产生的pCTs有最好的体素明智的，几何和放射学的协议与真实的CT，紧随其后的图集为基础的方法。在剂量测定的准确性，补丁为基础的方法的平均偏差小于0.5%的措施有关的目标coverage.Conclusions：我们表明，补丁为基础的方法可以产生一个准确的pCT的基础上，传统的T-1加权MRI序列和无变形登记。在我们的评估中，该方法比现有的基于体素和基于图谱的方法表现得更好，并且显示出仅基于MRI的大脑RT的有希望的潜力。(C)2015年美国医学物理学家协会。
Purpose: In radiotherapy (RT) based on magnetic resonance imaging (MRI) as the only modality, the information on electron density must be derived from the MRI scan by creating a so-called pseudo computed tomography (pCT). This is a nontrivial task, since the voxel-intensities in an MRI scan are not uniquely related to electron density. To solve the task, voxel-based or atlas-based models have typically been used. The voxel-based models require a specialized dual ultrashort echo time MRI sequence for bone visualization and the atlas-based models require deformable registrations of conventional MRI scans. In this study, we investigate the potential of a patch-based method for creating a pCT based on conventional T-1-weighted MRI scans without using deformable registrations. We compare this method against two state-of-the-art methods within the voxel-based and atlas-based categories.Methods: The data consisted of CT and MRI scans of five cranial RT patients. To compare the performance of the different methods, a nested cross validation was done to find optimal model parameters for all the methods. Voxel-wise and geometric evaluations of the pCTs were done. Furthermore, a radiologic evaluation based on water equivalent path lengths was carried out, comparing the upper hemisphere of the head in the pCT and the real CT. Finally, the dosimetric accuracy was tested and compared for a photon treatment plan.Results: The pCTs produced with the patch-based method had the best voxel-wise, geometric, and radiologic agreement with the real CT, closely followed by the atlas-based method. In terms of the dosimetric accuracy, the patch-based method had average deviations of less than 0.5% in measures related to target coverage.Conclusions: We showed that a patch-based method could generate an accurate pCT based on conventional T-1-weighted MRI sequences and without deformable registrations. In our evaluations, the method performed better than existing voxel-based and atlas-based methods and showed a promising potential for RT of the brain based only on MRI. (C) 2015 American Association of Physicists in Medicine.