Diffusion-weighting Caused by Spoiler Gradients in the Fast Imaging with Steady-state Precession Sequence May Lead to Inaccurate T(2) Measurements in MR Fingerprinting

Magnetic resonance fingerprinting (MRF) is a promising framework that allows the quantification of multiple magnetic resonance parameters with a single scan. MRF using fast imaging with steady-state precession (MRF-FISP) has robustness to off-resonance artifacts and has many applications in inhomogeneous fields. However, the spoiler gradient used in MRF-FISP is sensitive to diffusion motion, and may lead to quantification errors when the spoiler moment increases. In this study, we examined the effect of the diffusion weighting in MRF-FISP caused by spoiler gradients. The T(2) relaxation times were greatly underestimated when large spoiler moments were used. The T(2) underestimation was prominent for tissues with large values of T(2) and diffusion coefficients. The T(2) bias was almost independent of the apparent diffusion coefficient (ADC) and T(2) values when the ADC map was measured and incorporated into the matching process. These results reveal that the T(2) underestimation resulted from the diffusion weighting caused by the spoiler gradients.