Hyperpolarized Xe-129 MRI of the rat brain with chemical shift saturation recovery and spiral-IDEAL readout

Purpose To demonstrate the feasibility of Xe-129 chemical shift saturation recovery (CSSR) combined with spiral-IDEAL imaging for simultaneous measurement of the time-course of red blood cell (RBC) and brain tissue signals in the rat brain. Methods Images of both the RBC and brain tissue Xe-129 signals from the brains of five rats were obtained using interleaved spiral-IDEAL imaging following chemical shift saturation pulses applied at multiple CSSR delay times, tau. A linear fit of the signals to tau was used to calculate the slope of the signal for both RBC and brain tissue compartments on a voxel-by-voxel basis. Gas transfer was evaluated by measuring the ratio of the whole brain tissue-to-RBC signal intensities as a function of tau. To investigate the relationship between the CSSR images and gas transfer in the brain, the experiments were repeated during hypercapnic ventilation. Results Hypercapnia, affected the ratio of the tissue-to-RBC signal intensity (p = 0.026), consistent with an increase in gas transfer. Conclusion CSSR with spiral-IDEAL imaging is feasible for acquisition of Xe-129 RBC and brain tissue time-course images in the rat brain. Differences in the time-course of the signal intensity ratios are consistent with gas transfer changes expected under hypercapnic conditions.