Generalized k-space decomposition with chemical shift correction for non-cartesian water-fat Imaging
Generalized k-space decomposition with chemical shift correction for non-cartesian water-fat Imaging
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DOI：
10.1002/mrm.21580
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发表时间：
2008-05-01
影响因子：
3.3
通讯作者：
Reeder, Scott B.
中科院分区：
文献类型：
--
作者：
Brodsky, Ethan K.;Holmes, James H.;Reeder, Scott B.
与传统自旋扭曲笛卡尔成像中发生的大量脂肪位移相比，与非笛卡尔成像相关的化学位移伪影建模起来更复杂，并且临床上更难以接受。引入了一种基于回波不对称和最小二乘估计 (IDEAL) 方法的新型基于 k 空间的水和脂肪迭代分解，该方法可分解多个物质，同时纠正非共振物质的失真。新的信号模型考虑了k空间采集轨迹中每个点处的非共振自旋累积的附加相位。然后，可以通过在最终 IDEAL 处理步骤期间调整每个 k 空间点的分解矩阵来校正该相位，而几乎不会增加重建时间。该技术通过使用投影重建（PR）/径向、螺旋和笛卡尔自旋扭曲成像对体模和人类受试者进行水脂肪分解来演示，在每种情况下都实现了化学位移伪影的实质性校正。检查非共振自旋点扩散函数 (PSF) 的模拟，以显示每次采集的化学位移畸变的性质。还介绍了一种改进具有多个共振峰的物种的信号模型的方法。许多化学物质，包括脂肪，具有多个共振峰，尽管这些物质通常被近似为单峰。通过水-脂肪成像证明了多峰分解的改进，显示出水-脂肪分离的显着改进。
Chemical-shift artifacts associated with non-Cartesian imaging are more complex to model and less clinically acceptable than the bulk fat shift that occurs with conventional spin-warp Cartesian imaging. A novel k-space based iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) approach is introduced that decomposes multiple species while simultaneously correcting distortion of off-resonant species. The new signal model accounts for the additional phase accumulated by off -resonant spins at each point in the k-space acquisition trajectory. This phase can then be corrected by adjusting the decomposition matrix for each k-space point during the final IDEAL processing step with little increase in reconstruction time. The technique is demonstrated with water-fat decomposition using projection reconstruction (PR)/radial, spiral, and Cartesian spin-warp imaging of phantoms and human subjects, in each case achieving substantial correction of chemical-shift artifacts. Simulations of the pointspread-function (PSF) for off-resonant spins are examined to show the nature of the chemical-shift distortion for each acquisition. Also introduced is an approach to improve the signal model for species which have multiple resonant peaks. Many chemical species, including fat, have multiple resonant peaks, although such species are often approximated as a single peak. The improved multipeak decomposition is demonstrated with water-fat imaging, showing a substantial improvement in water-fat separation.