HALF FOURIER RECONSTRUCTION OF SPIRAL MR IMAGES

介绍：传统k空间的部分采样 自旋扭曲成像已经成为减少回波时间的标准方式， 总收购时间 以类似的方式， 从交错螺旋k空间轨迹也是可能的， 仅获得交错数目的一半。 方法和 讨论：该方法依赖于 原始数据，因此对影响这一点的因素敏感 对称性，例如B0场不均匀性、B1相位变化、麦克斯韦 条款等。不幸的是，这些都是存在于 因此，在扫描仪中获取的数据的校正方法是 必需的. 螺旋成像中的半傅立叶重建依赖于 将螺旋欠采样伪像与期望的 成像。 不幸的是，在存在相位变化的情况下， 成像对象，这些伪影出现在一定的距离， 不均匀性的位置。 最简单的纠正方法是使用 二维零差校正类似于它在 自旋扭曲半傅立叶重建，但这并没有解决 非局部图像伪影的问题。 基波奈奎斯特 违反了采样限制，数据插值需要 构造较好的插值函数， 问题的准确性网格算法最常用的 螺旋图像重建 结论：该技术适用于 有望提高功能磁共振成像的时间分辨率 研究和使用螺旋成像序列的其他研究。

Introduction: Partial sampling of k-space in conventional spin-warp imaging has become a standard way of reducing echo times or total acquisition time. In an analogous way, reconstruction of images from interleaved spiral k-space trajectories is also possible where only half the number of interleaves are acquired. Methods and Discussion: This method relies on the Hermitian conjugate symmetry of the raw data and hence is sensitive to factors influencing this symmetry, such as B0 field inhomogeneity, B1 phase variation, Maxwell terms, etc. Unfortunately, these are all factors which are present in data acquired in the scanner therefore methods of correction are required. Half Fourier reconstruction in spiral imaging relies on putting the spiral undersampling artifact in quadrature to the desired imaged. Unfortunately, in the presence of phase variations in the imaged object, these artifacts appear at some distance from the location of the inhomogeneity. The simplest correction is to use a two dimensional homodyne correction similar to the way it is used in spin warp half Fourier reconstruction but this does not solve the problem of the non-localized image artifacts. Fundamental Nyquist sampling limits are being violated and interpolation of data requires the construction of better interpolation functions bringing into question the accuracy of the gridding algorithm most commonly used in spiral image reconstruction. Conclusion: This technique holds promise for improving the temporal resolution of functional MR imaging studies and other studies employing the spiral imaging sequence.