Novel MR imaging of anatomy and function based on intermolecular double-quantum coherences (iDQC)

Abstract

We obtained for the first time iDQC images of human brain and muscles at 1.5 T. These images are fundamentally different in information content and in imaging contrast from conventional MR images. Combined quantum mechanical and classical formalisms were used to characterize the iDQC signal, and to aid in the design of DQC imaging sequences with conventional or EPI acquisitions. Both our theoretical analysis and experiments suggest that signals from the DQCs have a higher sensitivity than those from the zero-quantum coherence (ZQC) for human brain imaging. The increase in magnetic field strength substantially enhances ZQC and DQC signal intensities, but the higher sensitivity of DQC over ZQC remains at higher fields. DQCs possess some favorable features. Their high selectivity to dipolar interactions of adjustable spatial scales and sensitivity to local susceptibility variation suggest they may be useful for detecting changes in local magnetic susceptibility such as in human brain activation, or in tumor oxygenation studies. They can also be used potentially to study short-, middle- and long-range dipolar interactions in different tissues. They have twice the sensitivity to molecular diffusion than measurements with diffusion of spins under single-quantum transition. The signal also lasts longer in the time domain. New applications based on these properties of DQC are presented, including relaxation and diffusion studies, and brain activation mapping with auditory stimulation.