Optimizing spoiling characteristics for gas-phase hyperpolarized 129Xe transmit RF calibration

Motivation: Manufacturer-supplied transmitter calibrations are unsuitable for 129Xe MRI due to the transient nature of its magnetization, but existing 129Xe calibration protocols exhibit incomplete spoiling that adversely affects accuracy in flip angle measurements. Goal(s): We sought to develop a new spoiling-gradient configuration for 129Xe MRI transmit calibration that corrects the incomplete spoiling and improves accuracy. Approach: Spoiling configurations were simulated, tested, and optimized in a water phantom. The optimal configuration was tested in subjects who underwent 129Xe MRI with both calibration schemes. Results: A configuration that increases spoiling-gradient moment with each FID corrected the incomplete spoiling and improved the accuracy of flip angle measurements. Impact: Implementing a 129Xe MRI transmit calibration that increases spoiling-gradient moment with each FID acquisition improves accuracy in flip angle calculations, thereby ensuring consistently optimal image quality for all subjects and advancing the clinical utility of 129Xe MRI.