Whole-brain high in-plane resolution fMRI using accelerated EPIK for enhanced characterisation of functional areas at 3T.

Seong Dae Yun,N Jon Shah,Nick Todd

doi:10.1371/journal.pone.0184759

Seong Dae Yun, N Jon Shah + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0184759

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Journal: PloS one	Publication Date: Sep 25, 2017
Citations: 15	License type: CC BY 4.0

Affiliation: Forschungszentrum Jülich, RWTH Aachen University

Abstract

The relatively high imaging speed of EPI has led to its widespread use in dynamic MRI studies such as functional MRI. An approach to improve the performance of EPI, EPI with Keyhole (EPIK), has been previously presented and its use in fMRI was verified at 1.5T as well as 3T. The method has been proven to achieve a higher temporal resolution and smaller image distortions when compared to single-shot EPI. Furthermore, the performance of EPIK in the detection of functional signals was shown to be comparable to that of EPI. For these reasons, we were motivated to employ EPIK here for high-resolution imaging. The method was optimised to offer the highest possible in-plane resolution and slice coverage under the given imaging constraints: fixed TR/TE, FOV and acceleration factors for parallel imaging and partial Fourier techniques. The performance of EPIK was evaluated in direct comparison to the optimised protocol obtained from EPI. The two imaging methods were applied to visual fMRI experiments involving sixteen subjects. The results showed that enhanced spatial resolution with a whole-brain coverage was achieved by EPIK (1.00 mm × 1.00 mm; 32 slices) when compared to EPI (1.25 mm × 1.25 mm; 28 slices). As a consequence, enhanced characterisation of functional areas has been demonstrated in EPIK particularly for relatively small brain regions such as the lateral geniculate nucleus (LGN) and superior colliculus (SC); overall, a significantly increased t-value and activation area were observed from EPIK data. Lastly, the use of EPIK for fMRI was validated with the simulation of different types of data reconstruction methods.

Highlights

Since the demonstration of blood-oxygenated-level-dependent (BOLD) contrast by Ogawa et al [1], numerous functional MRI imaging methods have been used in attempts to measure neural brain activity
In contrast to the original keyhole method, continuous high spatial-frequency updates in EPI with Keyhole (EPIK) ensure that only small parts of the periphery of k-space are correlated in a limited number of scans
For enhanced detection of neural signals in functional MRI (fMRI), a high-resolution imaging method based on EPIK has been demonstrated here at 3T

Summary

Introduction

Since the demonstration of blood-oxygenated-level-dependent (BOLD) contrast by Ogawa et al [1], numerous functional MRI (fMRI) imaging methods have been used in attempts to measure neural brain activity. EPI has been in widespread use in fMRI studies due to its relatively high temporal resolution. A single-shot EPI sequence can offer a spatial resolution of 2~3 mm in an acquisition time of 2~3 s for the whole human brain. This is sufficient for most fMRI applications, but not enough for applications. High-resolution fMRI using accelerated EPIK study design, data collection and analysis, decision to publish, or preparation of the manuscript. Except the funding sources declared above, there was no additional external funding received for this study

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