Inversion recovery TrueFISP:: Quantification of T1, T2, and spin density

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(*) less than or equal to 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. (C) 2004 Wiley-Liss, Inc.