Analysis and correction of biases in cross-relaxation MRI due to biexponential longitudinal relaxation.
Analysis and correction of biases in cross-relaxation MRI due to biexponential longitudinal relaxation.
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DOI：
10.1002/mrm.24677
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发表时间：
2014-02
影响因子：
3.3
通讯作者：
Samsonov, Alexey
中科院分区：
文献类型：
--
作者：
Mossahebi, Pouria;Yarnykh, Vasily L.;Samsonov, Alexey
交叉弛豫成像(CRI)是一种定量磁化传递(MT)技术，它利用由变翻转角度(VFA)方法重建的非共振饱和和纵向弛豫速率(R1)图获得的图像。最近的研究表明，由于MT诱导的水质子纵向弛豫的双指数行为，在富含大分子的组织中，表观VFA R1的估计存在显著的偏差。本文的目的是从理论和实验上表征CRI映射中产生的偏差，并提出纠正的方法。提出了修正的CRI算法(MCRI)，该算法纠正了这种偏差，并产生了精确的参数f、k和r1图。此外，还引入了分析校正程序来重新计算先前获得的参数值。由于未解释的双指数弛豫引起的系统误差可以表征为对r1、束缚池分数f和交叉弛豫速率k的高估，其相对偏差与f的大小相当。体模和人体实验表明，所提出的MCRI和解析校正方法都显著提高了CRI方法的精度。通过考虑MT诱导的双指数纵向弛豫对VFA R1测量的贡献，CRI方法的精度可以显著提高。
Cross-relaxation imaging (CRI) is a family of quantitative magnetization transfer (MT) techniques that utilize images obtained with off-resonance saturation and longitudinal relaxation rate (R1) maps reconstructed by the variable flip angle (VFA) method. It was demonstrated recently that a significant bias in apparent VFA R1 estimates occurs in macromolecule-rich tissues due to MT-induced bi-exponential behavior of longitudinal relaxation of water protons. The purpose of this paper is to characterize theoretically and experimentally the resulting bias in the CRI maps and propose methods to correct it. The modified CRI algorithm (mCRI) is proposed, which corrects for such bias and yields accurate parametric f, k, and R1 maps. Additionally, an analytical correction procedure is introduced to recalculate previously obtained parameter values. The systematic errors due to unaccounted bi-exponential relaxation can be characterized as overestimation of R1, bound pool fraction f, and cross-relaxation rate k, with a relative bias comparable with the magnitude of f. The phantom and human in vivo experiments demonstrate that both proposed mCRI and analytical correction approaches significantly improve accuracy of the CRI method. Accuracy of the CRI method can be considerably improved by taking into account the contribution of MT-induced bi-exponential longitudinal relaxation into VFA R1 measurements.
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影响因子：
64.8
作者：
EDZES, HT;SAMULSKI, ET
通讯作者：
SAMULSKI, ET
影响因子：
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作者：
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作者：
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影响因子：
3.3
作者：
Levesque, Ives R.;Pike, G. Bruce
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Pike, G. Bruce
影响因子：
3.3
作者：
Ou, Xiawei;Gochberg, Daniel Frank
通讯作者：
Gochberg, Daniel Frank