Integrated VASO and perfusion contrast: A new tool for laminar functional MRI

Chai, Yuhui; Li, Linqing; Huber, Laurentius; Poser, Benedikt A.; Bandettini, Peter A.

doi:10.1016/j.neuroimage.2019.116358

Cited by 45 publications

(70 citation statements)

References 38 publications

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“…The somatosensory CBV changes in response to whisker stimulation peak in the range of 5%-10% (compared to the baseline CBV). Such amplitudes are consistent with previously reported ΔCBV estimates in the pre-clinical domain (Hillman et al 2007;Kennerley et al 2005;2012a;Lee et al 2001;Tian et al 2010), whereas they are about 5-10 times smaller than previously reported VASO signal changes in humans (Beckett et al 2020;Chai et al 2019;Finn et al 2019;Guidi et al 2017;Huber et al 2018;Kurban et al 2020;Persichetti et al 2020;Yang and Yu 2019;Yu et al 2019).…”

Section: Concomitant Ois and Vasosupporting

confidence: 93%

“…The VASO CBV profile, however, also exhibits a similarly elevated CBV response in the superficial layers. This is consistent with previous layer-fMRI VASO studies (Beckett et al 2020;Chai et al 2019;Donahue et al 2017;Finn et al 2019;Guidi et al 2017;Huber et al 2014a;2017;Kurban et al 2020;Persichetti et al 2020;Yang and Yu 2019;Yu et al 2019) and might appear in conflict with the large body of preclinical studies. Note that the superficial activity in VASO profiles is located within the cortex and is approx 0.8 mm deeper than the GE-BOLD peak response above the cortical surface.…”

Section: Vaso Vs Mion Derived Cbv and Associated Cortical Profilingsupporting

confidence: 91%

“…Equally, conventional 2D singleshot EPI, Spin-echo (SE) BOLD techniques, while thought to be more specific to the microvasculature, and so better suited for the study of cortical columns (Koopmans and Yacoub 2019;Norris 2012), still demonstrate some weighting to the pial vessels (Goense and Logothetis 2006) due to significant intravascular dephasing effects (Boxermann et al 1995;Martindale et al 2008). To overcome these limitations and approach the mesoscopic spatial regime of cortical layers for brain function, alternative non-BOLD quantitative contrast mechanisms are required (Chai et al 2019;Huber et al 2019) in combination with modern hardware and readout regimes (Norris and Polimeni 2019; Yacoub and Wald 2018) -akin to the advances in structural based imaging. While an extensive range of techniques exists (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Slice selective slab-inversion (SS-SI) VASO is widely used across the literature for non-invasive imaging of microvascular layer-specific signal responses (Beckett et al 2020;Chai et al 2019;Finn et al 2019;Guidi et al 2017;Huber et al 2018;Kurban et al 2020;Persichetti et al 2020;Yang and Yu 2019;Yu et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Validating layer-specific VASO across species

Huber

Poser

Kaas

et al. 2020

Preprint

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Cerebral blood volume (CBV) has been shown to be a robust and important physiological parameter for quantitative interpretation of functional (f)MRI, capable of delivering highly localized mapping of neural activity. Indeed, with recent advances in ultra-high-field (>=7T) MRI hardware and associated sequence libraries, it has become possible to capture non-invasive CBV weighted fMRI signals across cortical layers. One of the most widely used approaches to achieve this (in humans) is through vascular-space-occupancy (VASO) fMRI. Unfortunately, the exact contrast mechanisms of layer-dependent VASO fMRI have not been validated and thus interpretation of such data is confounded. Here we cross-validate layer-dependent VASO fMRI contrast in a preclinical rat model using well established (but invasive) imaging methods in response to neuronal activation (somatosensory cortex) and respiratory challenge (hypercapnia). In particular VASO derived CBV measures are directly compared to concurrent measures of total haemoglobin changes from high resolution intrinsic optical imaging spectroscopy (OIS). Through direct comparison of response magnitude, across time, negligible changes in hematocrit ratio during activation (neuronal or vascular) are inferred. Quantified cortical layer profiling is demonstrated and in agreement between both VASO and contrast enhanced fMRI (using monocrystalline iron oxide nanoparticles, MION). Responses show high spatial localisation to layers of cortical excitatory and inhibitory processing independent of confounding large draining veins which hamper BOLD fMRI studies. While we find increased VASO based CBV reactivity (3.1 ± 1.2 fold increase) in humans compared to rats it is demonstrated that this reflects differences in stimulus design rather than confounds of the VASO signal source. Together, our findings confirm that the VASO contrast is indeed a reliable estimate of layer-specific CBV changes. This validation study increases the neuronal interpretability of human layer-dependent fMRI results and should supersede BOLD fMRI as the method of choice in neuroscience application studies.HighlightsOur goal is to validate layer-specific VASO fMRI with gold standard methodsLayer-specific VASO sequences are implemented for 7T imaging in humans and ratsComparisons of VASO, optical imaging, and MION confirm the expected contrast originSomatosensory stimulation in humans and rats reveal the same layer-fMRI signaturesWe confirm that VASO is a valid measure to estimate layer-specific neural activityGraphical abstract

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Section: Concomitant Ois and Vasosupporting

confidence: 93%

Section: Vaso Vs Mion Derived Cbv and Associated Cortical Profilingsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Validating layer-specific VASO across species

Huber

Poser

Kaas

et al. 2020

Preprint

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“…Recently, a novel fMRI approach called VAPER [78] has also been put forward as a contrast useful for perfusion-weighted high-resolution fMRI by mixing VASO and perfusion contrasts. Although the combination of two contrasts boosts VAPER's sensitivity, it markedly complicates its ability to quantify perfusion but also, its physiological specificity.…”

Section: Functional Bold and Perfusion Activationmentioning

confidence: 99%

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

Kashyap

Ivanov

Havlíček³

et al. 2020

Preprint

Self Cite

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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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Mapping of whole‐cerebrum resting‐state networks using ultra‐high resolution acquisition protocols

Yun

Pais‐Roldán

Palomero‐Gallagher

et al. 2022

Human Brain Mapping

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Resting‐state functional magnetic resonance imaging (fMRI) has been used in numerous studies to map networks in the brain that employ spatially disparate regions. However, attempts to map networks with high spatial resolution have been hampered by conflicting technical demands and associated problems. Results from recent fMRI studies have shown that spatial resolution remains around 0.7 × 0.7 × 0.7 mm 3 , with only partial brain coverage. Therefore, this work aims to present a novel fMRI technique that was developed based on echo‐planar‐imaging with keyhole (EPIK) combined with repetition‐time‐external (TR‐external) EPI phase correction. Each technique has been previously shown to be effective in enhancing the spatial resolution of fMRI, and in this work, the combination of the two techniques into TR‐external EPIK provided a nominal spatial resolution of 0.51 × 0.51 × 1.00 mm 3 (0.26 mm 3 voxel) with whole‐cerebrum coverage. Here, the feasibility of using half‐millimetre in‐plane TR‐external EPIK for resting‐state fMRI was validated using 13 healthy subjects and the corresponding reproducible mapping of resting‐state networks was demonstrated. Furthermore, TR‐external EPIK enabled the identification of various resting‐state networks distributed throughout the brain from a single fMRI session, with mapping fidelity onto the grey matter at 7T. The high‐resolution functional image further revealed mesoscale anatomical structures, such as small cerebral vessels and the internal granular layer of the cortex within the postcentral gyrus.

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Integrated VASO and perfusion contrast: A new tool for laminar functional MRI

Cited by 45 publications

References 38 publications

Validating layer-specific VASO across species

Validating layer-specific VASO across species

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

Mapping of whole‐cerebrum resting‐state networks using ultra‐high resolution acquisition protocols

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