Interleaved multinuclear Na+-H+-CEST-EPI metabolic MRI for simultaneously quantifying salinity and acidity

Extensive evidence suggests abnormal metabolism, sodium homeostasis, and tumor acidity are interconnected and play critical roles in brain tumor formation, progression, seizure activity, treatment resistance, and immune suppression. While Na+ and advanced H+ -based MRI techniques can provide this information, Na+ and H+ images are traditionally acquired sequentially, resulting in a total scan time exceeding what is clinically reasonable. In the current study, we demonstrate utility of a new interleaved sodium gradient echo and proton-based pH-sensitive amine chemical exchange saturation transfer echoplanar imaging (Na+-GRE/H+-CEST-EPI) sequence in 15 minutes, making it feasible to study patients with brain tumors.