Saskatchewan Univ., Saskatoon, Sask.
IEEE Trans Med Imaging. 1990;9(2):190-201. doi: 10.1109/42.56344.
A study of a novel nuclear magnetic resonance (NMR) chemical-shift image reconstruction method with a high chemical-shift resolution achieved by the chirp z-transform (CZT) is presented. Phase encoding is used for the spatial coordinates x and y, and the frequency coordinate is reserved especially for the chemical shift. The Fourier transform (FT) image reconstruction algorithm, which forms the basis of the new CZT image reconstruction method, is introduced. The novel method, using the CZT instead of the FT to evaluate the chemical-shift spectrum at a much higher resolution, is studied. The chemical-shift resolutions, achieved by the FT and the CZT, are studied theoretically from the aspect of the peak height and the peak width of chemical-shift spectra. The chemical-shift spectra calculated at a selected point in the image plane, and the chemical shift-images reconstructed by this method, are shown for a simple phantom containing ethanol and methanol at different locations. The results obtained by this method and by the FT method are compared and discussed. The experimental results have shown that a chemical-shift as small as 39 Hz, relative to the proton resonance frequency of 21.34 MHz, can be resolved successfully by this method without improvements in magnetic field homogeneity.
提出了一种利用啁啾 z 变换（CZT）实现高化学位移分辨率的新型核磁共振（NMR）化学位移图像重建方法的研究。相位编码用于空间坐标 x 和 y，而频率坐标专门用于化学位移。介绍了基于新 CZT 图像重建方法的傅里叶变换（FT）图像重建算法。研究了利用 CZT 而不是 FT 以更高分辨率评估化学位移谱的新方法。从化学位移谱的峰值高度和峰宽的角度，从理论上研究了 FT 和 CZT 实现的化学位移分辨率。显示了在图像平面上选择点处计算的化学位移谱和通过该方法重建的化学位移图像，对于包含不同位置的乙醇和甲醇的简单幻影。比较和讨论了该方法和 FT 方法得到的结果。实验结果表明，在磁场均匀度没有提高的情况下，该方法可以成功分辨出相对质子共振频率为 21.34 MHz 的 39 Hz 小的化学位移。
