Wang Deming, Doddrell David M, Cowin Gary
Centre for Magnetic Resonance, The University of Queensland, Brisbane 4072, Australia.
Magn Reson Imaging. 2004 May;22(4):529-42. doi: 10.1016/j.mri.2004.01.008.
A phantom that can be used for mapping geometric distortion in magnetic resonance imaging (MRI) is described. This phantom provides an array of densely distributed control points in three-dimensional (3D) space. These points form the basis of a comprehensive measurement method to correct for geometric distortion in MR images arising principally from gradient field non-linearity and magnet field inhomogeneity. The phantom was designed based on the concept that a point in space can be defined using three orthogonal planes. This novel design approach allows for as many control points as desired. Employing this novel design, a highly accurate method has been developed that enables the positions of the control points to be measured to sub-voxel accuracy. The phantom described in this paper was constructed to fit into a body coil of a MRI scanner, (external dimensions of the phantom were: 310 mm x 310 mm x 310 mm), and it contained 10,830 control points. With this phantom, the mean errors in the measured coordinates of the control points were on the order of 0.1 mm or less, which were less than one tenth of the voxel's dimensions of the phantom image. The calculated three-dimensional distortion map, i.e., the differences between the image positions and true positions of the control points, can then be used to compensate for geometric distortion for a full image restoration. It is anticipated that this novel method will have an impact on the applicability of MRI in both clinical and research settings, especially in areas where geometric accuracy is highly required, such as in MR neuro-imaging.
本文描述了一种可用于磁共振成像（MRI）中几何畸变映射的体模。该体模在三维（3D）空间中提供了一系列密集分布的控制点。这些点构成了一种综合测量方法的基础，用于校正主要由梯度场非线性和磁场不均匀性引起的MR图像中的几何畸变。该体模是基于空间中的一个点可以用三个正交平面来定义这一概念设计的。这种新颖的设计方法允许有任意数量的控制点。采用这种新颖的设计，已经开发出一种高精度方法，能够将控制点的位置测量到亚体素精度。本文所述的体模被制造成适合MRI扫描仪的体线圈（体模的外部尺寸为：310 mm×310 mm×310 mm），并且它包含10830个控制点。使用这个体模，控制点测量坐标的平均误差在0.1 mm或更小的量级，这小于体模图像体素尺寸的十分之一。然后，计算得到的三维畸变图，即控制点的图像位置与真实位置之间的差异，可用于补偿几何畸变以实现全图像恢复。预计这种新颖的方法将对MRI在临床和研究环境中的适用性产生影响，特别是在对几何精度要求很高的领域，如MR神经成像。
Zotero 插件