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  1. Article ; Online: Model-based iterative reconstruction for direct imaging with point spread function encoded echo planar MRI.

    Meyer, Nolan K / In, Myung-Ho / Black, David F / Campeau, Norbert G / Welker, Kirk M / Huston, John / Halverson, Maria A / Bernstein, Matt A / Trzasko, Joshua D

    Magnetic resonance imaging

    2024  Volume 109, Page(s) 189–202

    Abstract: Background: Echo planar imaging (EPI) is a fast measurement technique commonly used in magnetic resonance imaging (MRI), but is highly sensitive to measurement non-idealities in reconstruction. Point spread function (PSF)-encoded EPI is a multi-shot ... ...

    Abstract Background: Echo planar imaging (EPI) is a fast measurement technique commonly used in magnetic resonance imaging (MRI), but is highly sensitive to measurement non-idealities in reconstruction. Point spread function (PSF)-encoded EPI is a multi-shot strategy which alleviates distortion, but acquisition of encodings suitable for direct distortion-free imaging prolongs scan time. In this work, a model-based iterative reconstruction (MBIR) framework is introduced for direct imaging with PSF-EPI to improve image quality and acceleration potential.
    Methods: An MBIR platform was developed for accelerated PSF-EPI. The reconstruction utilizes a subspace representation, is regularized to promote local low-rankedness (LLR), and uses variable splitting for efficient iteration. Comparisons were made against standard reconstructions from prospectively accelerated PSF-EPI data and with retrospective subsampling. Exploring aggressive partial Fourier acceleration of the PSF-encoding dimension, additional comparisons were made against an extension of Homodyne to direct PSF-EPI in numerical experiments. A neuroradiologists' assessment was completed comparing images reconstructed with MBIR from retrospectively truncated data directly against images obtained with standard reconstructions from non-truncated datasets.
    Results: Image quality results were consistently superior for MBIR relative to standard and Homodyne reconstructions. As the MBIR signal model and reconstruction allow for arbitrary sampling of the PSF space, random sampling of the PSF-encoding dimension was also demonstrated, with quantitative assessments indicating best performance achieved through nonuniform PSF sampling combined with partial Fourier. With retrospective subsampling, MBIR reconstructs high-quality images from sub-minute scan datasets. MBIR was shown to be superior in a neuroradiologists' assessment with respect to three of five performance criteria, with equivalence for the remaining two.
    Conclusions: A novel image reconstruction framework is introduced for direct imaging with PSF-EPI, enabling arbitrary PSF space sampling and reconstruction of diagnostic-quality images from highly accelerated PSF-encoded EPI data.
    MeSH term(s) Retrospective Studies ; Echo-Planar Imaging/methods ; Brain/diagnostic imaging ; Algorithms ; Tomography, X-Ray Computed ; Image Processing, Computer-Assisted/methods
    Language English
    Publishing date 2024-03-13
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 604885-7
    ISSN 1873-5894 ; 0730-725X
    ISSN (online) 1873-5894
    ISSN 0730-725X
    DOI 10.1016/j.mri.2024.03.009
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Improved Resting-State Functional MRI Using Multi-Echo Echo-Planar Imaging on a Compact 3T MRI Scanner with High-Performance Gradients.

    Kang, Daehun / In, Myung-Ho / Jo, Hang Joon / Halverson, Maria A / Meyer, Nolan K / Ahmed, Zaki / Gray, Erin M / Madhavan, Radhika / Foo, Thomas K / Fernandez, Brice / Black, David F / Welker, Kirk M / Trzasko, Joshua D / Huston, John / Bernstein, Matt A / Shu, Yunhong

    Sensors (Basel, Switzerland)

    2023  Volume 23, Issue 9

    Abstract: In blood-oxygen-level-dependent (BOLD)-based resting-state functional (RS-fMRI) studies, usage of multi-echo echo-planar-imaging (ME-EPI) is limited due to unacceptable late echo times when high spatial resolution is used. Equipped with high-performance ... ...

    Abstract In blood-oxygen-level-dependent (BOLD)-based resting-state functional (RS-fMRI) studies, usage of multi-echo echo-planar-imaging (ME-EPI) is limited due to unacceptable late echo times when high spatial resolution is used. Equipped with high-performance gradients, the compact 3T MRI system (C3T) enables a three-echo whole-brain ME-EPI protocol with smaller than 2.5 mm isotropic voxel and shorter than 1 s repetition time, as required in landmark fMRI studies. The performance of the ME-EPI was comprehensively evaluated with signal variance reduction and region-of-interest-, seed- and independent-component-analysis-based functional connectivity analyses and compared with a counterpart of single-echo EPI with the shortest TR possible. Through the multi-echo combination, the thermal noise level is reduced. Functional connectivity, as well as signal intensity, are recovered in the medial orbital sulcus and anterior transverse collateral sulcus in ME-EPI. It is demonstrated that ME-EPI provides superior sensitivity and accuracy for detecting functional connectivity and/or brain networks in comparison with single-echo EPI. In conclusion, the high-performance gradient enabled high-spatial-temporal resolution ME-EPI would be the method of choice for RS-fMRI study on the C3T.
    MeSH term(s) Echo-Planar Imaging/methods ; Brain Mapping/methods ; Image Processing, Computer-Assisted/methods ; Magnetic Resonance Imaging/methods ; Brain/diagnostic imaging
    Language English
    Publishing date 2023-04-27
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2052857-7
    ISSN 1424-8220 ; 1424-8220
    ISSN (online) 1424-8220
    ISSN 1424-8220
    DOI 10.3390/s23094329
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Evaluation of a compact 3 T MRI scanner for patients with implanted devices.

    Bardwell Speltz, Lydia J / Shu, Yunhong / Watson, Robert E / Trzasko, Joshua D / In, Myung-Ho / Gray, Erin M / Halverson, Maria A / Tarasek, Matthew R / Hua, Yihe / Huston, John / Cogswell, Petrice M / Foo, Thomas K F / Bernstein, Matt A

    Magnetic resonance imaging

    2023  Volume 103, Page(s) 109–118

    Abstract: Access to high-quality MR exams is severely limited for patients with some implanted devices due to labeled MR safety conditions, but small-bore systems can overcome this limitation. For example, a compact 3 T MR scanner (C3T) with high-performance ... ...

    Abstract Access to high-quality MR exams is severely limited for patients with some implanted devices due to labeled MR safety conditions, but small-bore systems can overcome this limitation. For example, a compact 3 T MR scanner (C3T) with high-performance gradients can acquire exams of the head, extremities, and infants. Because of its reduced bore size and the patient being advanced only partially into the bore, the associated electromagnetic (EM) fields drop off rapidly caudal to the head, compared to whole-body systems. Therefore, some patients with MR conditional implanted devices can safely receive 3 T brain exams on the C3T using its strong gradients and a multiple-channel receive coil, while a corresponding exam on whole-body MR is precluded. The purpose of this study is to evaluate the performance of a small-bore scanner for subjects with MR conditional spinal or sacral nerve stimulators, or abandoned cardiac implantable electronic device (CIED) leads. The spatial dependence of specific absorption rate (SAR) on the C3T was compared to whole-body scanners. A device assessment tool was developed and applied to evaluate MR safety individually on the C3T for 12 subjects with implanted devices or abandoned CIED leads. Once MR safety was established, the subjects received a C3T brain exam along with their clinical, 1.5 T exam. The resulting images were graded by three board-certified neuroradiologists. The C3T exams were well-tolerated with no adverse events, and significantly outperformed the whole-body 1.5 T exams in terms of overall image quality.
    MeSH term(s) Humans ; Magnetic Resonance Imaging/methods ; Prostheses and Implants ; Brain/diagnostic imaging ; Heart ; Head
    Language English
    Publishing date 2023-07-17
    Publishing country Netherlands
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 604885-7
    ISSN 1873-5894 ; 0730-725X
    ISSN (online) 1873-5894
    ISSN 0730-725X
    DOI 10.1016/j.mri.2023.07.009
    Database MEDical Literature Analysis and Retrieval System OnLINE

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