Three-dimensional triple-quantum-filtered 23Na imaging of in vivo human brain

Abstract

A scheme for the generation of three-dimensional, triple-quantum- filtered (TQ) sodium images from normal human brain is presented. In this approach, a three-pulse, six-step, coherence transfer filter was used in conjunction with a fast twisted projection imaging sequence to generate spatial maps of the TQ signal across the entire brain. It is demonstrated, theoretically as well as experimentally, that the use of the three-pulse coherence filter leads to TQ sodium images in which the dependence of the image intensity on the spatial variation of the flip angle is less pronounced than it is in the 'standard,' four-pulse, TQ filter. Correction for the variation of the TQ signal intensity across the field of view because of radio-frequency (RF) inhomogeneity is straightforward with this approach. This imaging scheme allows the generation of RF inhomogeneity-corrected, TQ, sodium images from human brain at moderate field strength (3.0 T) in times acceptable for routine clinical examinations (20 minutes).