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

Abstract

A novel procedure is proposed to extract T₁, T₂, 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). This apparent relaxation time T ≤ T₁ depends on the flip angle as well as on both T₁ and T₂. Here, it is shown that the ratio T₁/T₂ 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 T₁, T₂, and relative spin density directly from the fit parameters. Phantom results show excellent agreement with single point reference measurements. In human volunteers T₁, T₂, and spin density maps in agreement with literature values were obtained. Magn Reson Med 51:661–667, 2004.