Generating patient specific pseudo-CT of the head from MR using atlas-based regression
Generating patient specific pseudo-CT of the head from MR using atlas-based regression
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DOI：
10.1088/0031-9155/60/2/825
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发表时间：
2015-01-21
影响因子：
3.5
通讯作者：
Knutsson, H.
中科院分区：
文献类型：
--
作者：
Sjolund, J.;Forsberg, D.;Knutsson, H.
PET图像的放射治疗计划和衰减校正需要模拟辐射传输。必要的物理特性通常来自计算机断层扫描（CT）图像，但在某些情况下，包括立体定向神经外科手术和组合PET/MR成像，只有磁共振（MR）图像可用。考虑到这些应用，我们描述了如何从解剖MR图像中获得逼真的，患者特定的，伪CT的头部。我们将该方法称为基于图谱的回归，因为它与基于图谱的分割相似。给定目标MR和包括MR和CT对的图谱数据库，基于图谱的回归通过将每个图谱MR配准到目标MR，将所得位移场应用于对应的图谱CT，最后，将变形的寰椎CT融合成单个伪CT，我们使用一种称为Morphon的可变形配准算法，并用一个确定性掩模对其进行增强，该掩模允许对某些区域允许具有的影响进行定制。注册。此外，我们提出了一种新的融合方法，其中变形CT的集合被迭代地注册到它们的联合平均值，并发现得到的平均CT变得更类似于目标CT。然而，体素中位数提供了更好的结果;至少与需要特殊MR成像技术的早期工作一样好。这使得基于图谱的回归成为临床应用的良好候选者。
Radiotherapy planning and attenuation correction of PET images require simulation of radiation transport. The necessary physical properties are typically derived from computed tomography (CT) images, but in some cases, including stereotactic neurosurgery and combined PET/MR imaging, only magnetic resonance (MR) images are available. With these applications in mind, we describe how a realistic, patient-specific, pseudo-CT of the head can be derived from anatomical MR images. We refer to the method as atlas-based regression, because of its similarity to atlas-based segmentation.Given a target MR and an atlas database comprising MR and CT pairs, atlas-based regression works by registering each atlas MR to the target MR, applying the resulting displacement fields to the corresponding atlas CTs and, finally, fusing the deformed atlas CTs into a single pseudo-CT.We use a deformable registration algorithm known as the Morphon and augment it with a certainty mask that allows a tailoring of the influence certain regions are allowed to have on the registration. Moreover, we propose a novel method of fusion, wherein the collection of deformed CTs is iteratively registered to their joint mean and find that the resulting mean CT becomes more similar to the target CT. However, the voxelwise median provided even better results; at least as good as earlier work that required special MR imaging techniques. This makes atlas-based regression a good candidate for clinical use.