MRI Research Center, Department of Physics, University of New Brunswick, 8 Bailey Drive, Fredericton, NB E3B 5A3, Canada.
J Magn Reson. 2013 Oct;235:6-14. doi: 10.1016/j.jmr.2013.07.003. Epub 2013 Jul 18.
In a FID based frequency encoding MRI experiment the central part of k-space is not generally accessible due to the probe dead time. This portion of k-space is however crucial for image reconstruction. SPRITE (Single Point Ramped Imaging with T1 Enhancement), SPI with a linearly ramped phase encode gradient, has been employed to image short relaxation time systems for many years with great success. It is a robust imaging method in significant measure because it provides acquisition of high quality k-space origin data. We propose a new sampling scheme, termed hybrid-SPRITE, combining phase and frequency encoding to ensure high quality images with reduced acquisition times, reduced gradient duty cycle and increased sensitivity. In hybrid-SPRITE, numerous time domain points are collected to assist image reconstruction. An Inverse Non-uniform Discrete Fourier Transform (INDFT) is employed in 1D applications. A pseudo-polar grid is exploited in 2D hybrid-SPRITE for rapid and accurate image reconstruction.
在基于 FID 的频率编码 MRI 实验中，由于探头死区时间，k 空间的中心部分通常无法访问。然而，k 空间的这一部分对于图像重建至关重要。SPRITE（带 T1 增强的单点 ramped 成像），具有线性 ramped 相位编码梯度的 SPI，多年来一直成功地用于对短弛豫时间系统进行成像。它是一种强大的成像方法，在很大程度上是因为它提供了高质量的 k 空间原点数据采集。我们提出了一种新的采样方案，称为混合-SPRITE，它结合了相位和频率编码，以确保在减少采集时间、降低梯度占空比和提高灵敏度的情况下获得高质量的图像。在混合-SPRITE 中，收集了大量的时域点来辅助图像重建。在 1D 应用中采用逆非均匀离散傅里叶变换（INDFT）。在 2D 混合-SPRITE 中利用伪极网格进行快速准确的图像重建。
