In vivo double quantum filtered sodium magnetic resonance imaging of human brain

Sodium signal from ordered environments can be selectively detected using a double-quantum magic angle (DQ-MA) sequence. This study presents the first DQ-MA sodium images of the human brain and evaluates the effect of preparation time (τ) on the signal.

Three phantoms of saline, agar gel, and xanthan gum were used to test the correct functioning of the DQ-MA sequence. Five healthy volunteers were imaged using DQ-MA with varying τ to determine the optimal preparation time. DQ-MA images were acquired with 1 or 2 averages and nominal resolution of 15 mm isotropic in 3.5 or 7 min, respectively. In addition, higher nominal resolution (8.4 mm isotropic) DQ-MA images were acquired from another subject in 48 min. Post hoc simulations were performed to explain the effect of τ on imaging results.

The DQ-MA sequence generates signal from only the xanthan gum phantom, correctly suppressing signal from environments in which the time-averaged quadrupolar interaction is expected to be zero (saline, agar). This sequence generates signal throughout the brain with maximum detection when τ=3 ms.

The existence of DQ-MA signal in the human brain indicates the presence of sodium nuclei in ordered environments and provides a novel contrast mechanism.