A Generalized Real-time Frequency Adjustment Approach for MRSI

Motivation: Spectroscopy is sensitive to frequency drift. After running sequences that have a high gradient duty-cycle, frequency continues to drift due to gradient cooling. Goal(s): To propose a generalized prospective real-time frequency correction that can be applied to imaging and spectroscopic sequences, where TR-variant and -invariant events are separable in time. Approach: Real-time frequency adjustment was implemented for CSI, using a navigator placed where the spin phase is consistent across TR cycles prior to the CSI readout. Results: Phantom measurements with the generalized navigator provide accurate estimates of the frequency drift, thereby minimizing spectral distortion and providing an improved baseline in the final spectra. Impact: Prospective real-time frequency adjustment using a generalized navigator approach, where the spin phase is consistent across TR cycles, can be applied to spectroscopic imaging to correct for frequency drift caused by gradient heating and cooling.