Schmitt Peter, Griswold Mark A, Jakob Peter M, Kotas Markus, Gulani Vikas, Flentje Michael, Haase Axel
Experimentelle Physik 5, Physikalisches Institut, Universität Würzburg, Germany.
Magn Reson Med. 2004 Apr;51(4):661-7. doi: 10.1002/mrm.20058.
A novel procedure is proposed to extract T(1), T(2), and relative spin density from the signal time course sampled with a series of TrueFISP images after spin inversion. Generally, the recovery of the magnetization during continuous TrueFISP imaging can be described in good approximation by a three parameter monoexponential function S(t) = S(stst)(1-INV exp(-t/T() (1)). This apparent relaxation time T() (1) <or= T(1) depends on the flip angle as well as on both T(1) and T(2). Here, it is shown that the ratio T(1)/T(2) can be directly extracted from the inversion factor INV, which describes the relation of the signal value extrapolated to t = 0 and the steady-state signal. Analytical expressions are given for the derivation of T(1), T(2), and relative spin density directly from the fit parameters. Phantom results show excellent agreement with single point reference measurements. In human volunteers T(1), T(2), and spin density maps in agreement with literature values were obtained.
提出了一种新方法，用于从自旋反转后一系列真稳态进动快速成像（TrueFISP）图像采样得到的信号时间历程中提取T(1)、T(2)和相对自旋密度。一般来说，连续真稳态进动快速成像过程中磁化强度的恢复可用三参数单指数函数S(t) = S(stst)(1 - INV exp(-t/T() (1))很好地近似描述。这个表观弛豫时间T() (1) ≤ T(1)取决于翻转角以及T(1)和T(2)两者。在此表明，T(1)/T(2)的比值可直接从反转因子INV中提取，该反转因子描述了外推到t = 0时的信号值与稳态信号之间的关系。给出了直接从拟合参数推导T(1)、T(2)和相对自旋密度的解析表达式。模型结果与单点参考测量结果高度吻合。在人体志愿者中获得了与文献值相符的T(1)、T(2)和自旋密度图。
