Invivo Corporation, Philips Healthcare, Gainesville, Florida 32608, USA.
Magn Reson Med. 2012 Jun;67(6):1547-55. doi: 10.1002/mrm.23135. Epub 2011 Oct 12.
Off-resonance artifacts hinder the wider applicability of echo-planar imaging and non-Cartesian MRI methods such as radial and spiral. In this work, a general and rapid method is proposed for off-resonance artifacts correction based on data convolution in k-space. The acquired k-space is divided into multiple segments based on their acquisition times. Off-resonance-induced artifact within each segment is removed by applying a convolution kernel, which is the Fourier transform of an off-resonance correcting spatial phase modulation term. The field map is determined from the inverse Fourier transform of a basis kernel, which is calibrated from data fitting in k-space. The technique was demonstrated in phantom and in vivo studies for radial, spiral and echo-planar imaging datasets. For radial acquisitions, the proposed method allows the self-calibration of the field map from the imaging data, when an alternating view-angle ordering scheme is used. An additional advantage for off-resonance artifacts correction based on data convolution in k-space is the reusability of convolution kernels to images acquired with the same sequence but different contrasts.
离频伪影阻碍了回波平面成像和非笛卡尔 MRI 方法（如径向和螺旋）的更广泛应用。在这项工作中，提出了一种基于 k 空间数据卷积的通用快速离频伪影校正方法。根据采集时间将采集的 k 空间划分为多个段。通过应用卷积核去除每个段内的离频诱导伪影，该卷积核是离频校正空间相位调制项的傅里叶变换。从基础核的逆傅里叶变换中确定磁场图，该基础核通过在 k 空间中进行数据拟合来校准。该技术在径向、螺旋和回波平面成像数据集的体模和体内研究中得到了验证。对于径向采集，当使用交替视角排序方案时，所提出的方法允许从成像数据中对磁场图进行自校准。基于 k 空间数据卷积的离频伪影校正的另一个优点是卷积核可重复用于具有相同序列但不同对比度的图像。
