Accelerated spin-echo fMRI using Multisection Excitation by Simultaneous Spin-echo Interleaving (MESSI) with complex-encoded generalized SLIce Dithered Enhanced Resolution (cgSlider) Simultaneous Multi-Slice Echo-Planar Imaging

Spin-echo functional MRI (SE-fMRI) has the potential to improve spatial specificity compared to gradient-echo fMRI. To address the challenge of achieving high spatiotemporal resolution SE-fMRI with large slice coverage due to long echo time (TE) and repetition times (TR), a new acquisition method called Multisection Excitation by Simultaneous Spin-echo Interleaving (MESSI) with complex-encoded generalized SLIce Dithered Enhanced Resolution (cgSlider) was developed. This technique takes advantage of the dead-time during the long TE by interleaving the excitation and readout of two slices, enabling 2x slice acceleration. Additionally, cgSlider utilizes the stable temporal background phase in SE-fMRI to encode and decode two adjacent slices simultaneously using a phase-constrained reconstruction method. The proposed cgSlider-MESSI technique was further combined with Simultaneous Multi-Slice (SMS) imaging to achieve additional slice acceleration. Using this combined approach, whole-brain SE-fMRI data could be acquired at a high spatiotemporal resolution of 1.5mm isotropic and a temporal resolution of 1.5s with a remarkable 32x encoding acceleration by combining RinplanexMBxcgSliderxMESSI=4x2x2x2. The performance of cgSlider-MESSI-SMS was evaluated using sensory stimulation and breathhold tasks at 3T and compared to conventional SE-SMS which provided comparable temporal signal to noise ratio while maintaining fourfold increase in slice coverage for same TR. The corresponding fMRI activation maps obtained from cgSlider-MESSI were consistent with those obtained from conventional SE-SMS demonstrating that high quality, high resolution whole brain SE fMRI can be acquired at short TR using cgSLIDER MESSI SMS. This advancement in SE fMRI acquisition method has the potential to improve spatial specificity and enable more detailed investigations of brain function.

Exploring the Potential of Spin-Echo Functional MRI (SE-fMRI) with Multisection Excitation by Simultaneous Spin-echo Interleaving (MESSI)

Functional Magnetic Resonance Imaging (fMRI) is a widely used imaging technique that allows researchers to study brain activity in real time. It has been used for decades to investigate various aspects of brain function, from cognitive processes to motor control. However, traditional fMRI techniques have limited spatial specificity due to long echo times (TE) and repetition times (TR). To address this challenge, researchers have developed a new acquisition method called Multisection Excitation by Simultaneous Spin-echo Interleaving (MESSI), which takes advantage of the dead-time during the long TE by interleaving the excitation and readout of two slices, enabling 2x slice acceleration. Additionally, MESSI utilizes a complex-encoded generalized SLIce Dithered Enhanced Resolution technique called cgSlider which uses the stable temporal background phase in SE-fMRI to encode and decode two adjacent slices simultaneously using a phase-constrained reconstruction method.

Combining MESSI with Simultaneous Multi-Slice Imaging

The proposed cgSlider–MESSI technique was further combined with Simultaneous Multi-Slice (SMS) imaging to achieve additional slice acceleration. Using this combined approach, whole brain SE–fMRI data could be acquired at a high spatiotemporal resolution of 1.5mm isotropic and a temporal resolution of 1.5s with an impressive 32x encoding acceleration by combining RinplanexMBxcgSLIDERxMESSI=4x2x2x2. This advancement in SE fMRI acquisition methods has the potential to improve spatial specificity and enable more detailed investigations into brain function than ever before possible.

Evaluating Performance

To evaluate performance, cgSLIDER–MESSI–SMS was tested using sensory stimulation and breathhold tasks at 3T and compared against conventional SE–SMS which provided comparable temporal signal to noise ratio while maintaining fourfold increase in slice coverage for same TR. The corresponding fMRI activation maps obtained from cgSLIDER–MESSI were consistent with those obtained from conventional SE–SMS demonstrating that high quality, high resolution whole brain SE fMRI can be acquired at short TR using cgSLIDER MESSI SMS without sacrificing accuracy or detail in comparison to traditional methods such as gradient echo fMRIs .

Conclusion

In conclusion, spin echo functional magnetic resonance imaging has great potential for improving spatial specificity compared to gradient echo fMRIs when combined with multisection excitation by simultaneous spin echo interleaving along with simultaneous multi slice imaging techniques such as cgSLIDER MESSSISMS . This advancement not only enables higher resolutions but also shorter repetition times resulting in faster scans that provide more accurate results than ever before possible while still maintaining excellent signal quality .