First In Vivo ²³Na Human Imaging at 10.5 T Using a Combined Sodium-Proton Transceiver Body Array

To demonstrate the first in vivo human ²³Na MRI at 10.5 T using a novel dual-tuned transceiver body array and to evaluate a self-gating approach for respiratory motion compensation, focusing on renal imaging.

A custom-built eight-channel ²³Na-loop ¹H-dipole transceiver array was designed, constructed, and characterized. Safe operation was ensured through comparison of electromagnetic simulations against B₁ ⁺ and SAR phantom measurements. A programmable motion phantom mimicked respiratory motion to assess self-gating for both the ²³Na and ¹H acquisitions. Finally, in vivo human abdominal ²³Na and ¹H data were acquired in three healthy volunteers under free breathing, applying the self-gating approach.

The array's electromagnetic model showed good agreement with experimental data, with B₁ ⁺ NRMSE values of 0.16 for ²³Na, 0.32 for ¹H, and SAR NRMSE values of 0.35 for ²³Na and 0.22 for ¹H. Total power limits of 125 and 42 W were implemented for ²³Na and ¹H, respectively. The motion phantom study confirmed that both ²³Na and ¹H self-gating signals accurately tracked the programmed ground truth motion (correlation coefficients: 0.979 for ²³Na, 0.995 for ¹H). Motion binning significantly improved image sharpness as quantitatively evaluated in the phantom. In vivo, self-gating robustly captured respiratory motion and effectively enabled motion compensation, as shown in binned images with enhanced anatomical detail.

We successfully performed the first in vivo human ²³Na MRI at 10.5 T. The developed dual-tuned array and validated self-gating technique enable 10.5 T imaging in humans, paving the way for quantitative studies of sodium homeostasis and advancing diagnostic capabilities.