Fast Determination of Flip Angle and T(1) in Hyperpolarized Gas MRI During a Single Breath-Hold

MRI of hyperpolarized media, such as (129)Xe and (3)He, shows great potential for clinical applications. The optimal use of the available spin polarization requires accurate flip angle calibrations and T(1) measurements. Traditional flip angle calibration methods are time-consuming and suffer from polarization losses during T(1) relaxation. In this paper, we propose a method to simultaneously calibrate flip angles and measure T(1) in vivo during a breath-hold time of less than 4 seconds. We demonstrate the accuracy, robustness and repeatability of this method and contrast it with traditional methods. By measuring the T(1) of hyperpolarized gas, the oxygen pressure in vivo can be calibrated during the same breath hold. The results of the calibration have been applied in variable flip angle (VFA) scheme to obtain a stable steady-state transverse magnetization. Coupled with this method, the ultra-short TE (UTE) and constant VFA (CVFA) schemes are expected to give rise to new applications of hyperpolarized media.