Overview and Critical Appraisal of Arterial Spin Labelling Technique in Brain Perfusion Imaging

Alsaedi, Amirah; Thomas, David L.; Bisdas, Sotirios; Golay, Xavier

doi:10.1155/2018/5360375

Cited by 28 publications

(26 citation statements)

References 59 publications

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“…This might result in artificial changes in signal intensity, which a clinician might mistake as a disease-related abnormality in CBF. Another barrier to the employment of ASL in clinical practice is its low signal to noise ratio, which leads to reductions in image quality [47]. …”

Section: Advanced Mr Techniquesmentioning

confidence: 99%

Magnetic resonance imaging in Alzheimer’s disease and mild cognitive impairment

et al. 2018

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Research utilizing magnetic resonance imaging (MRI) has been crucial to the understanding of the neuropathological mechanisms behind and clinical identification of Alzheimer's disease (AD) and mild cognitive impairment (MCI). MRI modalities show patterns of brain damage that discriminate AD from other brain illnesses and brain abnormalities that are associated with risk of conversion to AD from MCI and other behavioural outcomes. This review discusses the application of various MRI techniques to and their clinical usefulness in AD and MCI. MRI modalities covered include structural MRI, diffusion tensor imaging (DTI), arterial spin labelling (ASL), magnetic resonance spectroscopy (MRS), and functional MRI (fMRI). There is much evidence supporting the validity of MRI as a biomarker for these disorders; however, only traditional structural imaging is currently recommended for routine use in clinical settings. Future research is needed to warrant the inclusion for more advanced MRI methodology in forthcoming revisions to diagnostic criteria for AD and MCI.

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Section: Advanced Mr Techniquesmentioning

confidence: 99%

Magnetic resonance imaging in Alzheimer’s disease and mild cognitive impairment

et al. 2018

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“…However, the B1 + inhomogeneities remain a major hurdle [33]. While We were able to mitigate this to some extent using dielectric pads [50,51], Future studies will be able to take advantage of advances in parallel transmission (pTx) technology [102] or the use of dedicated labelling-only RF-coils [103][104][105][106] to potentially further optimise highresolution ASL fMRI at ultra-high fields.…”

Section: Limitationsmentioning

confidence: 99%

Sub-Millimetre Resolution Laminar Fmri Using Arterial Spin Labelling in Humans at 7 T

Kashyap

Ivanov

Havlíček³

et al. 2020

Preprint

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Laminar fMRI at ultra-high magnetic field strength is typically carried out using the Blood Oxygenation Level-Dependent (BOLD) contrast. Despite its unrivalled sensitivity to detecting activation, the BOLD contrast is limited in its spatial specificity due to signals stemming from intra-cortical ascending and pial veins. Alternatively, regional changes in perfusion (i.e., cerebral blood flow through tissue) are colocalised to neuronal activation, which can be non-invasively measured using arterial spin labelling (ASL) MRI. In addition, ASL provides a quantitative marker of neuronal activation in terms of perfusion signal, which is simultaneously acquired along with the BOLD signal. However, ASL for laminar imaging is challenging due to the lower SNR of the perfusion signal and higher RF power deposition i.e., specific absorption rate (SAR) of ASL sequences. In the present study, we present for the first time in humans, isotropic sub-millimetre spatial resolution functional perfusion images using Flow-sensitive Alternating Inversion Recovery (FAIR) ASL with a 3D-EPI readout at 7T. We show that robust statistical activation maps can be obtained with perfusion-weighting in a single session. We observed the characteristic BOLD amplitude increase towards the superficial laminae, and, in apparent discrepancy, the relative perfusion profile shows a decrease of the amplitude and the absolute perfusion profile a much smaller increase towards the cortical surface. Considering the draining vein effect on the BOLD signal using model-based spatial ‘convolution’, we show that the empirically measured perfusion and BOLD profiles are, in fact, consistent with each other. This study demonstrates that laminar perfusion fMRI in humans is feasible at 7T and that caution must be exercised when interpreting BOLD signal laminar profiles as direct representation of the cortical distribution of neuronal activity.

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“…Diffusion-weighted MRI (dMRI) (review (Moeller et al, 2020), and references therein), is one of these critically important techniques; it is currently the only non-invasive imaging method available to map short and long-range anatomical connections in the brain and to extract information on the white matter microstructure (Alexander et al, 2019). Complementing dMRI, there exists other MRI techniques such as resting state functional magnetic resonance imaging (rfMRI) employed for inferring functional connectivity from correlations in spontaneous temporal fluctuations (Smith et al, 2013), task based fMRI (tfMRI) that depicts regional responses to specific cognitive processes and stimuli (Barch et al, 2013), and arterial spin labeling (ASL), which is a method that provides quantitative measurements of cerebral blood flow (CBF) without the use exogenous contrast agents (Alsaedi et al, 2018). All of these methods are challenged by the inherently low signal-to-noise ratio (SNR) of the MR images themselves especially when ambitious improvements on spatial and/or temporal resolutions are sought, as foreseen, for example in the BRAIN Initiative in order to meet the enormous challenges faced in the effort to understand human brain function (Jorgenson et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

NOise Reduction with DIstribution Corrected (NORDIC) PCA in dMRI with complex-valued parameter-free locally low-rank processing

Moeller

Pishardy

Ramanna

et al. 2020

Preprint

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Diffusion-weighted magnetic resonance imaging (dMRI) has found great utility for a wide range of neuroscientific and clinical applications. However, high-resolution dMRI, which is required for improved delineation of fine brain structures and connectomics, is hampered by its low signal-to-noise ratio (SNR). Since dMRI relies on the acquisition of multiple different diffusion weighted images of the same anatomy, it is well-suited for denoising methods that utilize correlations across the image series to improve the apparent SNR and the subsequent data analysis. In this work, we introduce and quantitatively evaluate a comprehensive framework, NOise Reduction with DIstribution Corrected (NORDIC) PCA method for processing dMRI. NORDIC uses low-rank modeling of g-factor-corrected complex dMRI reconstruction and non-asymptotic random matrix distributions to remove signal components which cannot be distinguished from thermal noise. The utility of the proposed framework for denoising dMRI is demonstrated on both simulations and experimental data obtained at 3 Tesla with different resolutions using human connectome project style acquisitions. The proposed framework leads to substantially enhanced quantitative performance for estimating diffusion tractography related measures and for resolving crossing fibers as compared to a conventional/state-of-the-art dMRI denoising method.HighlightsWe propose a framework, NORDIC, for denoising complex valued dMRI data using Gaussian statisticsThe effectiveness of the proposed denoising method is distinguished by the ability to remove only signal which cannot be distinguished from thermal noiseThe proposed method outperforms a state-of-art method for denoising dMRI in terms of fiber orientation dispersionQuantitative evaluation of NORDIC across different resolutions and SNR using human connectome type acquisitions and analysis shows up to 6 fold improvement in apparent SNR for 0.9mm whole brain dMRI at 3T.

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Overview and Critical Appraisal of Arterial Spin Labelling Technique in Brain Perfusion Imaging

Cited by 28 publications

References 59 publications

Magnetic resonance imaging in Alzheimer’s disease and mild cognitive impairment

Magnetic resonance imaging in Alzheimer’s disease and mild cognitive impairment

Sub-Millimetre Resolution Laminar Fmri Using Arterial Spin Labelling in Humans at 7 T

NOise Reduction with DIstribution Corrected (NORDIC) PCA in dMRI with complex-valued parameter-free locally low-rank processing

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