Peters R D, Wood M L
Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Center (Imaging Research), Ontario, Canada.
J Magn Reson Imaging. 1996 May-Jun;6(3):529-40. doi: 10.1002/jmri.1880060317.
This paper explores an alternative to standard Fourier MRI called wavelet-transform encoding. Spatially selective radiofrequency (RF) pulses are used to excite slice profiles in the shape of the wavelet-basis functions of a discrete wavelet transform. Our implementation on a standard commercial whole body MRI system resolves one spatial dimension through wavelet encoding and orthogonal directions through conventional frequency encoding and rectangular-slice selection. The wavelet transform is described as a method for multiresolution analysis, and we show how a high resolution MR image can be constructed from lower resolution images, representing the approximation and detail structures of the object. A multiple level architecture of the wavelet reconstruction is described, thereby allowing wavelet-encoded images to be reconstructed through several modes. Multilevel wavelet-encoded images of a gel phantom are presented that show comparable image quality to Fourier-encoded images of similar signal-to-noise ratio. However, a chemical-shift artifact is identified with this particular implementation.
本文探索了一种名为小波变换编码的标准傅里叶磁共振成像替代方法。空间选择性射频（RF）脉冲用于激发离散小波变换的小波基函数形状的切片轮廓。我们在标准商用全身磁共振成像系统上的实现通过小波编码解析一个空间维度，并通过传统频率编码和矩形切片选择解析正交方向。小波变换被描述为一种多分辨率分析方法，并且我们展示了如何从较低分辨率图像构建高分辨率磁共振图像，这些较低分辨率图像表示物体的近似和细节结构。描述了小波重建的多级架构，从而允许通过几种模式重建小波编码图像。给出了凝胶体模的多级小波编码图像，其显示出与具有相似信噪比的傅里叶编码图像相当的图像质量。然而，在此特定实现中识别出了化学位移伪影。
