Sodium-23 magnetic resonance imaging during and after transient cerebral ischemia: multinuclear stroke protocols for double-tuned 23Na/1H resonator systems

A double-tuned Na-23/H-1 resonator system was developed to record multinuclear MR image data during and after transient cerebral ischemia. H-1-diffusion-, H-1 perfusion, H-1 T2-, H-1 arterial blood flow-and Na-23 spin density-weighted images were then acquired at three time points in a rodent stroke model: (I) during 90 min artery occlusion, (II) directly after arterial reperfusion and (III) one day after arterial reperfusion. Normal Na-23 was detected in hypoperfused stroke tissue which exhibited a low H-1 apparent diffusion coefficient (ADC) and no changes in H-1 T-2 relaxation time during transient ischemia, while Na-23 increased and ADC values recovered to normal values directly after arterial reperfusion. For the first time, a similar imaging protocol was set-up on a clinical 3T MRI site in conjunction with a commercial double-tuned H-1/Na-23 birdcage resonator avoiding a time-consuming exchange of resonators or MRI systems. Multinuclear Na-23/H-1 MRI data sets were obtained from one stroke patient during both the acute and non-acute stroke phases with an aquisition time of 22 min. The lesion exhibiting low ADC was found to be larger compared to the lesion with high Na-23 at 9 h after symptom onset. It is hoped that the presented pilot data demonstrate that fast multinuclear Na-23/H-1 MRI preclinical and clinical protocols can enable a better understanding of how temporal and regional MRI parameter changes link to pathophysiological variations in ischemic stroke tissue.