Addressing phase errors in fat-water imaging using a mixed magnitude/complex fitting method.
Addressing phase errors in fat-water imaging using a mixed magnitude/complex fitting method.
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DOI：
10.1002/mrm.23044
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发表时间：
2012-03
影响因子：
3.3
通讯作者：
Reeder, S. B.
中科院分区：
文献类型：
--
作者：
Hernando, D.;Hines, C. D. G.;Yu, H.;Reeder, S. B.
非酒精性脂肪性肝病的早期诊断和定量分期需要对肝脏脂肪含量进行准确、无创的测量。基于化学位移的脂肪定量方法使用多回波扰相梯度回波序列在多个回波时间获取图像，并通过后处理提供脂肪分数测量值。然而，诸如由涡流引起的相位误差会对脂肪定量产生不利影响。这些相位误差通常在回波链的第一个回波处最为显著，并在基于复数的脂肪定量技术中引入偏差。使用基于幅度的技术（丢弃所有回波的相位）可以克服这些误差，但代价是信噪比显著降低，特别是对于某些回波时间组合的选择。在这项工作中，我们开发了一种重建方法，该方法克服了这些相位误差，且没有因幅度拟合而导致信噪比下降。这种方法丢弃第一个回波的相位（该相位通常已损坏），同时保留其余回波的相位（此处相位未改变）。我们在104个患者肝脏数据集（来自52名患者，每人扫描两次）上测试了所提出的方法，将脂肪分数测量值与配准的光谱测量值进行了比较。我们证明，混合拟合能够在广泛的回波组合选择中提供具有高信噪比和低偏差的准确脂肪分数测量值。
Accurate, noninvasive measurements of liver fat content are needed for the early diagnosis and quantitative staging of nonalcoholic fatty liver disease. Chemical shift-based fat quantification methods acquire images at multiple echo times using a multiecho spoiled gradient echo sequence, and provide fat fraction measurements through postprocessing. However, phase errors, such as those caused by eddy currents, can adversely affect fat quantification. These phase errors are typically most significant at the first echo of the echo train, and introduce bias in complex-based fat quantification techniques. These errors can be overcome using a magnitude-based technique (where the phase of all echoes is discarded), but at the cost of significantly degraded signal-to-noise ratio, particularly for certain choices of echo time combinations. In this work, we develop a reconstruction method that overcomes these phase errors without the signal-to-noise ratio penalty incurred by magnitude fitting. This method discards the phase of the first echo (which is often corrupted) while maintaining the phase of the remaining echoes (where phase is unaltered). We test the proposed method on 104 patient liver datasets (from 52 patients, each scanned twice), where the fat fraction measurements are compared to coregistered spectroscopy measurements. We demonstrate that mixed fitting is able to provide accurate fat fraction measurements with high signal-to-noise ratio and low bias over a wide choice of echo combinations.
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影响因子：
3.3
作者：
Hernando, Diego;Liang, Zhi-Pei;Kellman, Peter
通讯作者：
Kellman, Peter
影响因子：
3.3
作者：
Pineda, AR;Reeder, SB;Pelc, NJ
通讯作者：
Pelc, NJ
影响因子：
3.3
作者：
Hernando, Diego;Kellman, P.;Haldar, J. P.;Liang, Z-P.
通讯作者：
Liang, Z-P.
影响因子：
3.3
作者：
Ma, JF
通讯作者：
Ma, JF
影响因子：
3.3
作者：
Brodsky, Ethan K.;Holmes, James H.;Reeder, Scott B.
通讯作者：
Reeder, Scott B.