In Vivo Blood T1 Measurements at 1.5 T, 3 T, and 7 T

The longitudinal relaxation time of blood is a crucial parameter for quantification of cerebral blood flow by arterial spin labeling and is one of the main determinants of the signal-to-noise ratio of the resulting perfusion maps. Whereas at low and medium magnetic field strengths (B-0), its in vivo value is well established; at ultra-high field, this is still uncertain. In this study, longitudinal relaxation time of blood in the sagittal sinus was measured at 1.5 T, 3 T, and 7 T. A nonselective inversion pulse preceding a Look-Locker echo planar imaging sequence was performed to obtain the inversion recovery curve of venous blood. The results showed that longitudinal relaxation time of blood at 7 T was approximate to 2.1 s which translates to an anticipated 33% gain in the signal-to-noise ratio in arterial spin labeling experiments due to T-1 relaxation alone compared with 3 T. In addition, the linear relationship between longitudinal relaxation time of blood and B-0 was confirmed. Magn Reson Med, 70:1082-1086, 2013. (c) 2012 Wiley Periodicals, Inc.