Imperfect spoiling in variable flip angle T1 mapping at 7T: Quantifying and minimizing impact
Nadège Corbin, Martina F. Callaghan
Abstract
Purpose
The variable flip angle (VFA) approach to T1 mapping assumes perfectly spoiled transverse magnetisation at the end of each repetition time (TR). Despite radiofrequency (RF) and gradient spoiling, this condition is rarely met, leading to erroneous T1 estimates (
). Theoretical corrections can be applied but make assumptions about tissue properties, for example, a global T2 time. Here, we investigate the effect of imperfect spoiling at 7T and the interaction between the RF and gradient spoiling conditions, additionally accounting for diffusion. We provide guidance on the optimal approach to maximise the accuracy of the T1 estimate in the context of 3D multi-echo acquisitions.
Methods
The impact of the spoiling regime was investigated through numerical simulations, phantom and in vivo experiments.
Results
The predicted dependence of on tissue properties, system settings, and spoiling conditions was observed in both phantom and in vivo experiments. Diffusion effects modulated the dependence of on both 
efficiency and T2 times.
Conclusion
Error in can be minimized by using an RF spoiling increment and gradient spoiler moment combination that minimizes T2-dependence and safeguards image quality. Although the diffusion effect was comparatively small at 7T, correction factors accounting for this effect are recommended.