A two-step scheme for distortion rectification of magnetic resonance images
A two-step scheme for distortion rectification of magnetic resonance images
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DOI：
10.1118/1.3180107
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发表时间：
2009-09-01
期刊：
影响因子：
3.8
通讯作者：
Fallone, B. Gino
中科院分区：
文献类型：
--
作者：
Baldwin, Lesley N.;Wachowicz, Keith;Fallone, B. Gino
这项工作的目的是展示一个完整的，鲁棒的，和时间效率的方法来校正磁共振（MR）图像失真。众所周知，MR图像存在与机器相关的空间扭曲[梯度非线性和主场（B-0）不均匀性]和与患者相关的空间扭曲（易感性和化学位移伪影），并且对基于MR的放射治疗计划领域日益增长的兴趣对此类图像的几何精度提出了新的要求。作者提出了一种两步方法，结合了基于幽灵的反梯度技术，用于测量梯度非线性和基于患者的相位差映射技术，用于测量B-0不均匀性，敏感性和化学位移畸变。相位差映射技术只增加了患者总扫描时间的几分钟，并且可以用于校正同一患者和解剖结构的各种图像。这项技术在几个不同的幻影上进行了测试，每个幻影都被设计成隔离一种变形。梯度回波和自旋回波图像的平均畸变减小到0.2 +/- 0.1 mm。对于高度失真的平面回波图像，残差被降至亚体素级。作为最后一步，该技术在患者图像上实现。目前的技术是有效的，时间效率高，鲁棒性强，并为准备畸变校正磁共振图像提供了希望，用于基于磁共振的治疗计划。(C) 2009年美国医学物理学家协会。(DOI: 10.1118/1.3180107)
The aim of this work is to demonstrate a complete, robust, and time-efficient method for distortion correction of magnetic resonance (MR) images. It is well known that MR images suffer from both machine-related spatial distortions [gradient nonlinearity and main field (B-0) inhomogeneity] and patient-related spatial distortions (susceptibility and chemical shift artifacts), and growing interest in the area of MR-based radiotherapy treatment planning has put new requirements on the geometric accuracy of such images. The authors present a two-step method that combines a phantom-based reverse gradient technique for measurement of gradient nonlinearities and a patient-based phase difference mapping technique for measurement of B-0 inhomogeneities, susceptibility, and chemical shift distortions. The phase difference mapping technique adds only minutes to the total patient scan time and can be used to correct a variety of images of the same patient and anatomy. The technique was tested on several different phantoms, each designed to isolate one type of distortion. The mean distortion was reduced to 0.2 +/- 0.1 mm in both gradient echo and spin echo images of a grid phantom. For the more difficult case of a highly distorted echo planar image, residual distortion was reduced to subvoxel dimensions. As a final step, the technique was implemented on patient images. The current technique is effective, time efficient, and robust and provides promise for preparing distortion-rectified MR images for use in MR-based treatment planning. (C) 2009 American Association of Physicists in Medicine. [DOI: 10.1118/1.3180107]