Impact of Magnetization Transfer on Relaxometry using Transient Steady-State Free Precession Imaging

Introduction. Several methods proposed the use of the transient response of balanced steady-state free precession (bSSFP) for quantification of relaxation times and spin densities [1-3]. After inversion, the transition to steady state closely follows a mono-exponential signal behavior with an apparent relaxation rate T1* [1,4], which depends on the flip angle, T1 and T2. However, it has been shown that magnetization transfer (MT) affects the steady state of bSSFP and is dependent on pulse duration and repetition time [5]. Furthermore, it has been shown that MT effects can lead to an overestimation of T1 for spoiled gradient echo [6]. During transition to steady state also MT effects built up, thus it is likely that MT affects the estimation of relaxation parameters using inversion recovery bSSFP [1,2] and similar transient SSFP methods [3]. In this work, we will show exemplarily for inversion recovery bSSFP [1] that significant deviations arise from MT leading to deviations in calculated T1 and T2 by 30-60%.