School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore, Singapore.
Magn Reson Med. 2013 May;69(5):1297-309. doi: 10.1002/mrm.24359. Epub 2012 Jun 12.
A novel B-Spline based approach to phase unwrapping in tagged magnetic resonance images is proposed for cardiac motion tracking. A bicubic B-spline surface is used to model the absolute phase. The phase unwrapping problem is formulated as a mixed integer optimization problem that minimizes the sum of the difference between the spatial gradients of absolute and wrapped phases, and the difference between the rewrapped and wrapped phases. In contrast to the existing techniques for motion tracking, the proposed approach can overcome the limitation of interframe half-tag displacement and increase the robustness of motion tracking. The article further presents a hybrid harmonic phase imaging-B-spline method to take the advantage of the harmonic phase imaging method for small motion and the efficiency of the B-Spline approach for large motion. The proposed approach has been successively applied to a full set of cardiac MRI scans in both long and short axis slices with superior performance when compared with the harmonic phase imaging and quality guided path-following methods.
提出了一种新的基于 B 样条的相位解缠方法，用于标记磁共振图像中的心脏运动跟踪。使用双三次 B 样条曲面来建模绝对相位。相位解缠问题被表述为一个混合整数优化问题，该问题最小化绝对相位和包裹相位的空间梯度之间的差异之和，以及重缠绕相位和包裹相位之间的差异之和。与现有的运动跟踪技术相比，所提出的方法可以克服帧间半标记位移的限制，并提高运动跟踪的鲁棒性。本文进一步提出了一种混合谐相成像-B 样条方法，以利用谐相成像方法在小运动中的优势和 B 样条方法在大运动中的效率。与谐相成像和质量引导路径跟踪方法相比，所提出的方法已成功应用于一组完整的心脏 MRI 扫描，在长轴和短轴切片中均具有优异的性能。
