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 (approximately T2) and iDQC evolution time tau(approximately 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.
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 (approximately T2) and iDQC evolution time tau(approximately 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.
Authors: W S Warren; S Ahn; M Mescher; M Garwood; K Ugurbil; W Richter; R R Rizi; J Hopkins; J S Leigh Journal: Science Date: 1998-07-10 Impact factor: 47.728