Variable flip angle T 1 mapping in the human brain with reduced t 2 sensitivity using fast radiofrequency‐spoiled gradient echo imaging

Purpose Variable flip angle (VFA) T 1 quantification using three‐dimensional (3D) radiofrequency (RF) spoiled gradient echo imaging offers the acquisition of whole‐brain T 1 maps in clinically acceptable times. However, conventional VFA T 1 relaxometry is biased by incomplete spoiling (i.e., residual T 2 dependency). A new postprocessing approach is proposed to overcome this T 2 ‐related bias. Methods T 1 is quantified from the signal ratio of two spoiled gradient echo (SPGR) images acquired at different flip angles using an analytical solution for the RF‐spoiled steady‐state signal in combination with a global T 2 guess. T 1 accuracy is evaluated from simulations and in vivo 3D SPGR imaging of the human brain at 3 Tesla. Results The simulations demonstrated that the sensitivity of VFA T 1 mapping to T 2 can considerably be reduced using a global T 2 guess. The method proved to deliver reliable and accurate T 1 values in vivo for white and gray matter in good agreement with inversion recovery reference measurements. Conclusion Based on a global T 2 estimate, the accuracy of VFA T 1 relaxometry in the human brain can substantially be improved compared with conventional approaches which rely on the generally wrong assumption of ideal spoiling. Magn Reson Med 75:1413–1422, 2016. © 2015 Wiley Periodicals, Inc.