Analysis of the Precision of Variable Flip Angle T(1) Mapping with Emphasis on the Noise Propagated from RF Transmit Field Maps.
Analysis of the Precision of Variable Flip Angle T(1) Mapping with Emphasis on the Noise Propagated from RF Transmit Field Maps.
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DOI：
10.3389/fnins.2017.00106
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发表时间：
2017
影响因子：
4.3
通讯作者：
Nagy Z
中科院分区：
文献类型：
--
作者：
Lee Y;Callaghan MF;Nagy Z
在磁共振成像中，纵向弛豫时间（T1）的精确测量对于获取适用于许多临床和神经科学应用的有用信息至关重要。在这项工作中，我们调查的精度T1弛豫时间测量使用可变翻转角的方法，重点是从射频发射场（）测量传播的噪声。T1精度的解析解是通过标准误差传播方法推导出来的，该方法将来自三个输入源的噪声合并：两个扰相梯度回波（SPGR）图像和一个标测图。重复的体内实验进行估计T1地图的总方差，我们比较这些实验获得的值与理论预测，以验证所建立的理论框架。分析和实验结果表明，在地图的方差传播到T1地图的噪声水平相当的两个SPGR图像。提高测量精度显著降低了估计T1图的方差。从重复测量的体内T1图估计的方差与理论计算的T1估计方差一致，从而验证了现实的体内实验的分析框架。我们的结论是，对于T1映射实验，必须考虑从映射传播的误差。优化SPGR信号而忽略提高地图的精度可能导致严重高估估计的T1值的精度。
In magnetic resonance imaging, precise measurements of longitudinal relaxation time (T1) is crucial to acquire useful information that is applicable to numerous clinical and neuroscience applications. In this work, we investigated the precision of T1 relaxation time as measured using the variable flip angle method with emphasis on the noise propagated from radiofrequency transmit field () measurements. The analytical solution for T1 precision was derived by standard error propagation methods incorporating the noise from the three input sources: two spoiled gradient echo (SPGR) images and a map. Repeated in vivo experiments were performed to estimate the total variance in T1 maps and we compared these experimentally obtained values with the theoretical predictions to validate the established theoretical framework. Both the analytical and experimental results showed that variance in the map propagated comparable noise levels into the T1 maps as either of the two SPGR images. Improving precision of the measurements significantly reduced the variance in the estimated T1 map. The variance estimated from the repeatedly measured in vivo T1 maps agreed well with the theoretically-calculated variance in T1 estimates, thus validating the analytical framework for realistic in vivo experiments. We concluded that for T1 mapping experiments, the error propagated from the map must be considered. Optimizing the SPGR signals while neglecting to improve the precision of the map may result in grossly overestimating the precision of the estimated T1 values.