Guoxiang Liu1,2, Adnan Shah1,2, Takashi Ueguchi1,2, Hideto Kuribayashi3
1NICT, Osaka, Japan, 2Osaka University, Osaka, Japan, 3Siemens Healthcare K.K, Tokyo, Japan
Osaka, Japan|Osaka, Japan
Osaka, Japan|Osaka, Japan
Compared to GE-EPI sequence, slice-selective slab-inversion vascular-space-occupancy (SS-SI-VASO)  provides higher specificity towards the microvasculature by reducing the sensitivity of extravascular signal contributions from larger veins. However, applying the inversion pulse in SS-SI-VASO sequence causes lower SNR, which limits the application in super high-resolution fMRI studies. Block-Interleaved Segmented EPI (BISEPI)  allows us to investigate submillimeter-level brain activity without GRAPPA to keep SNR by realigning the k-space trajectory based on a block design stimulation. In this work, we applied SS-SI-VASO with tailored RF pulse (TRFOCI)  in our BISEPI sequence to reduce SAR and make fast repetition of shot possible. After checking the sequence by phantom, we performed finger tapping task to test the specificity of BOLD signal from grey matter and CSF in high resolution (0.75 x 0.75 x 0.80 mm3) at 7T.
One adult human participant was scanned using 3D SS-SI-VASO BISEPI sequence on a Siemens MAGNETOM 7T prototype scanner with a 32-channel phased array head coil (Nova Medical, MA, USA) to obtain imaging data, where 320 fMRI volumes each at a spatial resolution of 0.75×0.75×0.80 mm3 were acquired. The acquisition parameters for functional scans were as follows: TR = 1500 ms, TE = 20 ms, flip angle (FA) = 30°, # segments = 3, # shots in block = 40, PF = 6/8. To obtain both VASO and BOLD signals, TRFOCI  pulses were applied only in odd volumes with an inversion slab 140 mm, inversion time (TI) 1100 ms. A right-hand finger tapping task was performed in experiment using BISEPI design  with ON and OFF for 30 s each. One normal multi-shot EPI volume was acquired as a reference before BISEPI acquisition. In post-processing stage, each shot of BISEPI acquired data was reconstructed to shot-separated volumes (GRAPPA = 3) for motion detection, the motion information was then obtained using SPM-12 by comparing the difference between the reference image and each single shot image. Before the final reconstruction, BISEPI data were motion corrected shot-wise separately in k-space . After functional scans, anatomical images were acquired with TI = 1400 ms and TR = 6000 ms using the same distortion related parameters. Even volumes (without inversion pulse applied) were used as BOLD series, while VASO series were generated by odd volumes divided by even volumes (VASO=odd/even). BrainVoyager and Matlab were used for data pre-processing and analysis.
We confirmed the performance of our k-space based motion correction approach , compared the VASO and BOLD response, checked the location difference of the active regions. Figure 1 (A) shows the subject motion information without motion correction. Figure 1(B) shows the remaining motion after k-space based motion correction in odd and even volumes. The remaining motions are substantially smaller than no motion correction case. Figure 2 shows the active regions detected by GLM approach in BrainVoyager. Compared to BOLD, there were no VASO response located at CSF regions.
·Figure 1: Motion information before and after shot-wise separate k-space motion correction. A) without motion correction. B) motion correction results in odd and even volumes.
·Figure 2: BOLD (A) and VASO (B) response.
TRFOCI-based SS-SI-VASO technique can be performed in BISEPI sequence, enabling VASO studies in high resolution (0.75 x 0.75 x 0.80 mm3) at 7T. Shot-wise separate motion correction substantially decreased motion outliers thus providing benefit for the analysis of fMRI data acquired using BISEPI. The proposed method can be used to improve localization of brain activity in submillimeter level high-resolution fMRI studies.
Novel Imaging Acquisition Methods:
Non-BOLD fMRI 1
Imaging Methods Other 2
HIGH FIELD MR
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 Huber L, Handwerker DA, Jangraw DC, et al. High-resolution CBV-fMRI allows mapping of laminar activity and connectivity of cortical input and output inhuman M1. Neuron 2017; 96(6): https://doi.org/10.1016/j.neuron.2017.11.005.
 Liu G, Shah A, Ueguchi T. Block-Interleaved segmented EPI for voxel-wise high-resolution fMRI studies at 7T. Proceedings of the International Society for Magnetic Resonance in Medicine Joint Annual Meeting ISMRM-ESMRMB. 2018;5450.
 Hurley AC, Al-Radaideh A, Bai L, Aickelin U, Coxon R, Glover P, Gowland PA. Tailored RF pulse for magnetization inversion at ultrahigh field. Magn Reson Med 2010;63:51–58.
 Liu G, Shah A, Ueguchi T, Ogawa S. Shot-wise separate motion correction and ICA denoising for BISEPI high-resolution fMRI study at 7T. ISMRM 2021. (submitted).