Functional MRI at 3T using intermolecular double-quantum coherence (iDQC) with spin-echo (SE) acquisitions

Object To reinvestigate the dependence of the signal and contrast on sequence parameters and tissue relaxation times for intermolecular double-quantum coherence (iDQC) signals, and to explore the possibility to use a spin-echo (SE)-iDQC sequence for detecting activation signals at 3T. Materials and methods Brain activations were detected in five human volunteers in a visual simulation study using a SE-iDQC sequence, in addition to a GE-iDQC and a conventional single-quantum coherence (SQC) blood-oxygenation-level-dependent (BOLD) sequence. A brain phantom was also used for some quantitative measurements. Results By choosing an optimal echo time TE (~T2) and iDQC evolution time τ(~20 ms), robust brain activations were detected using the SE-iDQC sequence, in addition to the GE-iDQC and a conventional single-quantum coherence (SQC) BOLD sequence. A higher percentage signal change due to activation was observed for both the iDQC-based measurements in comparison to the conventional SQC acquisition. Conclusion Even though a phenomenological analysis consistent with the experimental results was provided, a detailed model is still needed for the contrast mechanism at microscopic level to guide potential applications of brain functional imaging based on the SE-iDQC.