Accurate determination of spin-density and T1 in the presence of RF-field inhomogeneities and flip-angle miscalibration
Accurate determination of spin-density and T1 in the presence of RF-field inhomogeneities and flip-angle miscalibration
复制标题
DOI：
10.1002/mrm.1910400412
复制
发表时间：
1998-10-01
影响因子：
3.3
通讯作者：
Haacke, EM
中科院分区：
文献类型：
--
作者：
Venkatesan, R;Lin, WL;Haacke, EM
提出了一种在存在射频场不均匀性和翻转角失配的情况下精确提取相对自旋密度（rho（0））和自旋晶格弛豫时间（T-1）的方法。该方法需要在多个翻转角下用三维、扰动稳态、梯度回波成像序列收集图像，结果表明，过高估计的翻转角的主要影响是将T-1估计值移动到更高的值，而归一化RF场从1的减少导致rho（0）和T-1分布向更低的值倾斜。体模和体内实验结果表明，该方法克服了这两个系统误差。该方法被证明是有效的射频灵敏度降低高达50%。使用自洽参数来验证在大量体素上提取的rho（0）和T-1值中不存在系统误差，这使得可以在1.5 T下获得非常精确的肌肉T-1估计值，产生95%置信区间（1077.7 +/- 3.5）ms。
A method is presented for the accurate extraction of relative spin-density (rho(0)) and spin-lattice relaxation time (T-1) in the presence of RF-field inhomogeneities and flip-angle miscalibration, The method requires collecting images at several flip-angles with a three-dimensional, spoiled steady-state, gradient-echo imaging sequence, Results show that the predominant effect of an overestimated flip-angle is to shift the T-1 estimate to a higher value, whereas reductions in the normalized RF-field from unity cause rho(0) and T-1 distributions to be skewed toward lower values. Phantom and in vivo results demonstrate that the proposed method overcomes both of these systematic errors. The method was shown to be valid for up to a 50% reduction in RF sensitivity. A self-consistency argument was used to validate the absence of systematic errors in the extracted rho(0) and T-1 values over a large number of voxels, This made it possible to obtain a very precise estimate of muscle T-1 at 1.5 T, yielding a 95% confidence interval of (1077.7 +/- 3.5) ms.