Otazo Ricardo, Lin Fa-Hsuan, Wiggins Graham, Jordan Ramiro, Sodickson Daniel, Posse Stefan
Electrical and Computer Engineering Department, University of New Mexico, Albuquerque, NM, USA.
Neuroimage. 2009 Aug 1;47(1):220-30. doi: 10.1016/j.neuroimage.2009.03.049. Epub 2009 Mar 31.
Standard parallel magnetic resonance imaging (MRI) techniques suffer from residual aliasing artifacts when the coil sensitivities vary within the image voxel. In this work, a parallel MRI approach known as Superresolution SENSE (SURE-SENSE) is presented in which acceleration is performed by acquiring only the central region of k-space instead of increasing the sampling distance over the complete k-space matrix and reconstruction is explicitly based on intra-voxel coil sensitivity variation. In SURE-SENSE, parallel MRI reconstruction is formulated as a superresolution imaging problem where a collection of low resolution images acquired with multiple receiver coils are combined into a single image with higher spatial resolution using coil sensitivities acquired with high spatial resolution. The effective acceleration of conventional gradient encoding is given by the gain in spatial resolution, which is dictated by the degree of variation of the different coil sensitivity profiles within the low resolution image voxel. Since SURE-SENSE is an ill-posed inverse problem, Tikhonov regularization is employed to control noise amplification. Unlike standard SENSE, for which acceleration is constrained to the phase-encoding dimension/s, SURE-SENSE allows acceleration along all encoding directions--for example, two-dimensional acceleration of a 2D echo-planar acquisition. SURE-SENSE is particularly suitable for low spatial resolution imaging modalities such as spectroscopic imaging and functional imaging with high temporal resolution. Application to echo-planar functional and spectroscopic imaging in human brain is presented using two-dimensional acceleration with a 32-channel receiver coil.
当线圈灵敏度在图像体素内变化时，标准的并行磁共振成像（MRI）技术会受到残余混叠伪影的影响。在这项工作中，提出了一种称为超分辨率灵敏度编码（SURE - SENSE）的并行MRI方法，其中通过仅采集k空间的中心区域来实现加速，而不是在整个k空间矩阵上增加采样间距，并且重建明确基于体素内线圈灵敏度变化。在SURE - SENSE中，并行MRI重建被公式化为一个超分辨率成像问题，即利用高空间分辨率采集的线圈灵敏度，将通过多个接收线圈采集的一组低分辨率图像组合成具有更高空间分辨率的单个图像。传统梯度编码的有效加速由空间分辨率的提高给出，这由低分辨率图像体素内不同线圈灵敏度分布的变化程度决定。由于SURE - SENSE是一个不适定的逆问题，因此采用蒂霍诺夫正则化来控制噪声放大。与标准灵敏度编码不同，标准灵敏度编码的加速被限制在相位编码维度，而SURE - SENSE允许沿所有编码方向加速——例如，对二维回波平面采集进行二维加速。SURE - SENSE特别适用于低空间分辨率成像模式，如具有高时间分辨率的光谱成像和功能成像。使用32通道接收线圈进行二维加速，展示了其在人类大脑回波平面功能和光谱成像中的应用。
