Abstract
Recently, the main issue in neuroscience has been the imaging of the functional connectivity in the brain. No modality that can measure functional connectivity directly, however, has been developed yet. Here, we show the novel MRI sequence, called the partial spinlock sequence toward direct measurements of functional connectivity. This study investigates a probable measurement of phase differences directly associated with functional connectivity. By employing partial spinlock imaging, the neural magnetic field might influence the magnetic resonance signals. Using simulation and phantom studies to model the neural magnetic fields, we showed that magnetic resonance signals vary depending on the phase of an externally applied oscillating magnetic field with non-right flip angles. These results suggest that the partial spinlock sequence is a promising modality for functional connectivity measurements.
Highlights
Comprehending brain activity is promising to conquer psychiatric and neurological disorders and develop emerging technologies, such as the brain-machine interface and neurocomputers
We found that the positions of the current dipoles could be estimated to the positions that the sign of the signal change was reversed because the method directly measured magnetic fields, unlike the blood oxygenation level-dependent (BOLD)-functional magnetic resonance imaging (fMRI)
We investigated the plausibility of a spinlock module with non-right RF pulse for functional connectivity measurements both in Bloch simulations and a phantom study
Summary
Comprehending brain activity is promising to conquer psychiatric and neurological disorders and develop emerging technologies, such as the brain-machine interface and neurocomputers. The other group measures metabolic changes as a proxy for neuronal activities, such as oxygen and glucose concentrations The former include electroencephalography (EEG)[1,2] and magnetoencephalography (MEG)[3,4], having fine temporal resolution but coarse spatial resolution. This study proposes to modify the SIRS with non-right α and −α RF pulses, called the partial spinlock sequence, and clarify the effect of the phase of the oscillating fields on the MR signals acquired by the partial spinlock sequence. This method can measure phase differences among multiple sources by projecting the phase information to the MR signal intensities. We simulated the magnetisation behaviour with the Bloch equation, including phase effects and performed phantom measurements with a loop-coil phantom and current-dipole phantoms
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