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

A double-tuned ²³Na/¹H resonator system was developed to record multinuclear MR image data during and after transient cerebral ischemia. ¹H-diffusion-, (¹H perfusion, ¹H T₂-, ¹H arterial blood flow- and ²³Na 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 ²³Na was detected in hypoperfused stroke tissue which exhibited a low ¹H apparent diffusion coefficient (ADC) and no changes in ¹H T₂ relaxation time during transient ischemia, while ²³Na 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 ¹H/²³Na birdcage resonator avoiding a time-consuming exchange of resonators or MRI systems. Multinuclear ²³Na/¹H 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 ²³Na at 9 h after symptom onset. It is hoped that the presented pilot data demonstrate that fast multinuclear ²³Na/¹H 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.