RAPID INVIVO PROTON SHIMMING
RAPID INVIVO PROTON SHIMMING
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DOI：
10.1002/mrm.1910180208
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发表时间：
1991-04-01
影响因子：
3.3
通讯作者：
GLOVER, G
中科院分区：
文献类型：
--
作者：
SCHNEIDER, E;GLOVER, G
本文介绍了一种快速、全自动调节磁场均匀性的方法。Bo不均匀性图由梯度回波脉冲序列生成，其中选择频率分散以消除脂肪/水化学位移的影响。低阶匀场值通过幅度加权最小二乘拟合B 0图得出，并自动作为DC偏移应用于X、Y和Z梯度放大器。使用具有化学位移选择性饱和的成像作为该技术的功效的量度。结果表明，AUTOSHIM改善了整体均匀性;然而，某些空气/组织和骨/组织形态会产生无法通过线性梯度校正的局部高阶场失真。在这种情况下，可以在有限的感兴趣区域上应用“缩放SHIM”，以牺牲其他区域为代价来改善局部均匀性。有人建议，这样的扫描是必要的记录在临床MR波谱的均匀性。中国科学技术出版社. Inc.
A rapid and completely automated method of adjusting the magnetic field (B0) homogeneity forin vivoproton spectroscopy and imaging is described. Bo inhomogeneity maps are generated by a gradient‐recalled echo pulse sequence in which the frequency dispersion is chosen to eliminate the effects of the fat/water chemical shift. Low‐order shim values are derived by magnitude‐weighted least‐squares fits to theB0maps and automatically applied as DC offsets to theX, Y, and Z gradient amplifiers. Imaging with chemical shift selective saturation is used as a measure of the efficacy of the technique. Results indicate that AUTOSHIM improves the overall homogeneity; however, local high‐order field distortions which cannot be corrected by linear gradients are generated by certain air/tissue and bone/tissue morphology. In such cases a “ZOOM SHIM” may be applied over a limited region of interest for local homogeneity improvement at the expense of other regions. It is suggested that such scans are a necessity for recording the homogeneity during clinical MR spectroscopy. © 1991 Academic Press. Inc.