T-2 accuracy on a whole-body imager
T-2 accuracy on a whole-body imager
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DOI：
10.1002/mrm.1910380512
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发表时间：
1997-11-01
影响因子：
3.3
通讯作者：
Wright, GA
中科院分区：
文献类型：
--
作者：
Foltz, WD;Stainsby, JA;Wright, GA
MR血氧测定法要求T-2测量值在体内的准确度在5%以内。简单的方法容易受到信号丢失的影响，往往会低估T-2。当前的方法利用RF脉冲或RF循环模式，其防止在每次数据采集时的信号损失。然而，使用具有不完美脉冲的这些方法，由于磁化沿着纵轴的临时存储，T-2倾向于被高估，其中磁化以时间常数T-1 > T-2更慢地衰减。我们利用简单的90（x）180（y）90（x）复合脉冲和良好的RF循环模式，这些序列对于RF和静态场不均匀性和重新聚焦间隔的典型范围内的T-2精度是至关重要的，当脉冲宽度为重新聚焦间隔的10%或更多时，必须考虑每个90（x）180（y）90（x）脉冲期间的T-1信号衰减，以产生5%以内的精度，一个简单的校正方案有效地补偿了这种与T-1相关的误差。
MR oximetry requires a T-2, measurement that is accurate within 5% in vivo. Simple methods are susceptible to signal loss and tend to underestimate T-2. Current methods utilize RF pulses or RF cycling patterns that prevent signal loss at each data acquisition, However, using these methods with imperfect pulses, T-2 tends to be overestimated due to temporary storage of the magnetization along the longitudinal axis where it decays more slowly with a time constant T-1 > T-2 To reduce the T-1 dependence while preventing signal loss, we utilize simple 90(x)180(y)90(x) composite pulses and good RF cycling patterns, These trains are critical for T-2 accuracy over typical ranges of RF and static field inhomogeneities and refocusing intervals, T-1 signal decay during each 90(x)180(y)90(x) pulse must be accounted for to yield accuracy within 5% when the pulsewidth is 10% or more of the refocusing interval, A simple correction scheme compensates for this T-1-related error effectively.