Purpose: To evaluate the effect of an initial 90° depolarization RF pulse on the dissolved-phase hyperpolarized (HP) xenon-129 (129 Xe) brain imaging and to compare the SNR variability of HP 129 Xe images acquired without an initial depolarization RF pulse to those following the initial depolarization pulse.
Methods: Five cognitive normal healthy volunteers were imaged using a Philips Achieva 3.0T MRI scanner during a single breath-hold following inhalation of 1 L of HP 129 Xe. Each participant underwent six HP 129 Xe scans. Three scans were performed using conventional single-slice projection HP 129 Xe brain imaging, and the other three scans were performed using the HP 129 Xe time-of-flight imaging with an initial rectangular depolarization pulse.
Results: Although the utilization of an initial depolarization results in the reduction of the mean image SNR, the presence of an initial depolarization RF pulse reduces the SNR variability of the HP 129 Xe brain image by a factor of 2.26. The highest SNR variability was observed from the posterior brain region, where the anterior region possessed the lower level of signal variability.
Conclusion: An initial 90° depolarization RF pulse, applied prior to the HP 129 Xe image acquisition, reduced the HP 129 Xe signal variability more than two times between the different breath-hold images.
Keywords: depolarization pulse; dissolved phase imaging; hyperpolarized 129Xe brain imaging; hyperpolarized 129Xe time-of-flight; hyperpolarized xenon-129.
© 2021 International Society for Magnetic Resonance in Medicine.