High Spatial Resolution ²³Na-MRI for Ischemic Brain Injury Detection

High spatial resolution sodium (²³Na) imaging of brain lesions remains challenging due to the intrinsically low signal-to-noise ratio (SNR) of ²³Na-MRI compared with conventional proton (¹H) MRI. In this preclinical mouse study, we developed a high-resolution ²³Na-MRI platform based on a 14 T preclinical scanner using a dual-tuned head-implanted RF coil. This implanted coil configuration enabled longitudinal multimodal imaging in the same animal, including 1¹H-based T₂-weighted anatomical and diffusion-weighted imaging (DWI), and high-resolution ²³Na-MRI. To evaluate the capability of this approach for detecting acute ischemic injury, ischemic stroke was induced in mice using the middle cerebral artery occlusion (MCAO) model. Brain-wide ²³Na-MRI was acquired within the first 4 hours following MCAO at an in-plane resolution of 300 × 300 µm². Hyperintense ²³Na-MRI signals were observed in the ischemic brain regions, presenting a contrast-to-noise ratio (CNR) that exceeded that of T₂-weighted images. Infarct regions can be well identified by elevated ²³Na-MRI signal, which is spatially consistent with regions of reduced apparent diffusion coefficient (ADC) values, indicating water restriction in the ischemic core. This work established implanted dual-tuned ¹H/²³Na RF coils as a powerful approach for high-resolution ²³Na-MRI readout, facilitating the early detection of ischemic brain injury.