Lethmate R, Ratiney H, Wajer F T A W, Crémillieux Y, van Ormondt D, Graveron-Demilly D
Laboratoire de RMN, CNRS UMR 5012, Université Lyon I-CPE, 3 Rue Victor Grignard, 69616 Villeurbanne, France.
MAGMA. 2003 Feb;16(1):21-8. doi: 10.1007/s10334-003-0003-y.
A method - PA-keyhole - for 2D/3D dynamic magnetic resonance imaging with radial scanning is proposed. PA-keyhole exploits the inherent strong oversampling in the center of k-space, which contains crucial temporal information regarding contrast evolution. The method is based on: (1). a rearrangement of the temporal order of 2D/3D isotropic distributions of trajectories during the scan into subdistributions according to the desired time resolution, (2). a new post-acquisition keyhole approach based on the replacement of the central disk/sphere in k-space using data solely from a subdistribution, and (3). reconstruction of 2D/3D dynamic (time-resolved) images using 2D/3D-gridding with Pipe's approach to the sampling density compensation and 2D/3D-IFFT. The scan time is not increased with respect to a conventional 2D/3D radial scan of the same spatial resolution; in addition, one benefits from the dynamic information. The abilities of PA-keyhole and the sliding window techniques to restore simulated dynamic contrast changes are compared. Results are shown both for 2D and 3D dynamic imaging using experimental data. An application to in-vivo ventilation of rat lungs using hyperpolarized helium is demonstrated.
提出了一种用于二维/三维动态磁共振成像的径向扫描方法——PA锁孔技术。PA锁孔技术利用了k空间中心固有的强过采样，其中包含有关对比度演变的关键时间信息。该方法基于：（1）根据所需的时间分辨率，将扫描过程中二维/三维各向同性轨迹分布的时间顺序重新排列为子分布；（2）一种新的采集后锁孔方法，该方法基于仅使用子分布中的数据替换k空间中的中心圆盘/球体；（3）使用二维/三维网格化以及Pipe方法进行采样密度补偿和二维/三维逆快速傅里叶变换来重建二维/三维动态（时间分辨）图像。与具有相同空间分辨率的传统二维/三维径向扫描相比，扫描时间没有增加；此外，还能从动态信息中受益。比较了PA锁孔技术和滑动窗口技术恢复模拟动态对比度变化的能力。使用实验数据展示了二维和三维动态成像的结果。还展示了该技术在使用超极化氦对大鼠肺部进行体内通气方面的应用。
