Björn Fricke¹ and Jürgen Finsterbusch^1
1Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Cortico-spinal functional MRI covering a brain and a cervical spinal cord volume in the same acquisition, e.g. to investigate the interaction of brain and spinal cord areas, requires a dynamic shim update of the frequency and linear shim terms to obtain a reasonable EPI image quality in both volumes. Unfortunately, the optimum values for static higher-order and volume-specific dynamic linear shim terms cannot be determined with the standard shim algorithms provided by manufacturers. Here, a shim algorithm has been implemented that overcomes this problem and provides a better field homogeneity in the brain and spinal cord volumes.

Huilou Liang^1,2, Ziyi Pan³, Chencan Qian^1,2, Kaibao Sun¹, Fanhua Guo^1,2, Dehe Weng⁴, Jing An⁴, Yan Zhuo^1,2,5, Hua Guo³, Danny J.J. Wang⁶, and Rong Xue^1,2,7
1State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ²University of Chinese Academy of Sciences, Beijing, China, ³Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, ⁴Siemens Shenzhen Magnetic Resonance Ltd, Shenzhen, China, ⁵CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Beijing, China, ⁶Laboratory of FMRI Technology (LOFT), Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, CA, United States, ⁷Beijing Institute for Brain Disorders, Beijing, China

   In the past decade, passband bSSFP has emerged as an alternative method to the widely-used GE-EPI in fMRI studies at high-fields. Multiline bSSFP with an interleaved phase-encoding order was further proposed to accelerate bSSFP fMRI. However, it intrinsically suffers from high spatial frequency ghosts which blur the image. In this study, we developed a multi-echo bSSFP sequence using a sequential phase-encoding order, combined with the GRAPPA technique for ghost elimination. In vivo experiments demonstrated that this sequence could shorten the imaging time and provide high-quality structural and functional MR images of the human brain at 7T with sub-millimeter resolution.

Daehun Kang¹, Hang Joon Jo^1,2, Myung-Ho In¹, Erin Gray¹, Ek T Tan^3,4, Thomas K Foo⁴, Uten Yarach¹, Nolan K Meyer¹, Joshua D Trzasko¹, John Huston¹, Matt A Bernstein¹, and Yunhong Shu^1
1Mayo Clinic, Rochester, MN, United States, ²Hanyang University, Seoul, Republic of Korea, ³Hospital of Special Surgery, New York, NY, United States, ⁴GE Global Research, Niskayuna, NY, United States

Multi-echo fMRI has been shown to provide better denoising and result in improved functional analysis compared to single-echo acquisition, but it reduces the temporal resolution and inhibits high-resolution imaging. Multi-band imaging and in-plane acceleration can compensate for the reduced resolution. The high performance gradient on a compact 3T scanner can further reduce the echo-spacing and accelerate the acquisition. Here we demonstrate that high spatial-resolution ME-MB fMRI is achievable with high temporal resolution on the compact 3T. The effectiveness of ME acquisition is evaluated with different artifact reduction strategies in whole brain resting-state fMRI and compared with the standard SE acquisition.

Shihui Chen¹, Mei-Lan Chu², Queenie Chan³, Nan-Kuei Chen^4,5, Chun-Jung Juan⁶, Liyuan Liang¹, and Hing-Chiu Chang^1
1The University of Hong Kong, Hong Kong, Hong Kong, ²Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, Taipei, Taiwan, ³Philips Healthcare, Hong Kong, China, Hong Kong, Hong Kong, ⁴Department of Biomedical Engineering, University of Arizona, Tucson, AZ, United States, Tucson, AZ, United States, ⁵Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States, Durham, NC, United States, ⁶Department of Medical Imaging, China Medical University Hsinchu Hospital, Taiwan, Taipei, Taiwan

Multi-echo fMRI (ME-fMRI) has been shown to be useful in differentiating BOLD and non-BOLD signals, therefore improving the sensitivity of fMRI. Parallel imaging with high acceleration factor (e.g., R ≥ 3) is indispensable to achieve reasonable TE interval and desired spatial resolution for ME-fMRI acquisition. However, the reconstructed multi-echo images with high acceleration factor may suffer from underside noise amplification due to SENSE reconstruction. In this work, we further modify multi-echo multi-segment EPI (MEMS-EPI) technique with sliding window acquisition to acquire multi-echo fMRI with high acceleration factor, and then reconstruct highly accelerated multi-echo fMRI images with MUSE algorithm.

Wei Zhu¹, Djaudat Idiyatullin¹, Shinho Cho¹, Yi Zhang¹, Kâmil Uğurbil¹, Xiao-Hong Zhu¹, and Wei Chen^1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

Blood oxygenation-level dependent (BOLD) fMRI studies at the level mesoscopic organizations, such as cortical columns and layers, is challenged by the low signal-to-noise ratio (SNR) and the specificity of different fMRI sequences even at ultrahigh magnetic fields. In this work, we show that when mapping layer-specific activities in the cat visual cortex, ultrahigh-resolution 3D GRASE sequence with inner volume selection achieved similar specificity as at 9.4 Tesla CBV-fMRI using 2D GE-EPI sequence, while attains a higher BOLD sensitivity. Our results indicate that 3D iv-GRASE BOLD is promising for laminar and columnar mapping of brain functions.

Martin John MacKinnon¹, Sheng Song¹, Li-Ming Hsu¹, Sung-Ho Lee¹, G. Allan Johnson², and Yen-Yu Ian Shih^1
1University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, ²Duke University, Durham, NC, United States

In this study we demonstrate how a zero-echo-time (ZTE) technique can overcome several limitations of traditional fMRI experiments.  We demonstrate that ZTE fMRI can detect functional activations with positive iron oxide contrast, termed iZTE-fMRI, at an approximate three-fold magnitude increase in tCNR when compared to GRE-techniques in-vivo - with the further potential demonstrated from phantom studies to increase tCNR more significantly under optimal contrast agent dose. We also show that iZTE fMRI experiments can produce functional images with markedly less susceptibility artifacts and acoustic noise than standard GRE techniques.

Ekaterina Zhurakovskaya¹, Lauri Lehto¹, Jaakko Paasonen¹, Lin Wu², Sheng Sang², Jun Ma², Hanne Laakso¹, Tiina Pirttimäki¹, Olli Gröhn¹, Silvia Mangia², and Shalom Michaeli^2
1University of Eastern Finland, Kuopio, Finland, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Deep brain stimulation (DBS) is widely used to treat several disorders. Given its minimal sensitivity to electrode-induced artifacts, fMRI with Multi-Band Sweep Imaging with Fourier Transformation (MB-SWIFT) is a powerful tool for identifying the DBS mechanism of action at a network level. However, MB-SWIFT generally suffers from low time resolution, thus limiting the characterization of temporal features. Here, we introduce a novel resampling approach applicable to radial k-space sampling such as used in MB-SWIFT, allowing to track repeating events with 200-ms time resolution.  A proof of concept was demonstrated during DBS of the medial septal nucleus in rats.

Amos A Cao¹ and Douglas Noll^2
1University of Michigan, Ann Arbor, MI, United States, ²Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States

Oscillating Steady-State Imaging (OSSI) is a new steady-state sequence for high-SNR fMRI. Respiration-induced B0 changes cause undesirable changes to the OSSI steady-state, resulting in signal artifacts. To address this problem, we present a prospective correction method which utilizes a self-navigating spiral trajectory to measure and correct for B0 changes in real-time. In an initial fMRI proof-of-concept, our real-time correction method increased the number of activated voxels by 454% and increased mean tSNR by 81%. Real-time prospective correction has the potential to outperform retrospective correction methods by directly reducing perturbations to steady-state magnetization during acquisition.

Isa Costantini¹, Samuel Deslauriers-Gauthier¹, and Rachid Deriche^1
1Athena Project-Team, Inria Sophia Antipolis - Méditerranée, Université Côte d’Azur, Biot, France

In this work we propose and validate a Paradigm-Free fMRI (PFFMRI) algorithm that acts directly on the 4-D fMRI image and recover the underlying brain activations without knowledge on the experimental paradigm. PFFMRI is based on the idea that large image variations should be preserved as they occur during brain activation, but small variations should be smoothed to remove noise. Starting from this,  we were able to regularize the fMRI image with an anisotropic regularization, thus recovering the location of the brain activations in space and their timing and duration without knowledge of the experimental paradigm.