The human cerebellum has almost 80% of the surface area of the neocortex

© 2020 National Academy of Sciences. All rights reserved. The surface of the human cerebellar cortex is much more tightly folded than the cerebral cortex. It was computationally reconstructed for the first time to the level of all individual folia from multicontrast high-resolution postmortem MRI scans. Its total shrinkage-corrected surface area (1,590 cm2) was larger than expected or previously reported, equal to 78% of the total surface area of the human neocortex. The unfolded and flattened surface comprised a narrow strip 10 cm wide but almost 1 m long. By applying the same methods to the neocortex and cerebellum of the macaque monkey, we found that its cerebellum was relatively much smaller, approximately 33% of the total surface area of its neocortex. This suggests a prominent role for the cerebellum in the evolution of distinctively human behaviors and cognition

Whole brain 31P MRSI at 7T with a dual-tuned receive array

Purpose: The design and performance of a novel head coil setup for 31P spectroscopy at ultra‐high field strengths (7T) is presented. The described system supports measurements at both the 1H and 31P resonance frequencies. Methods: The novel coil consists of 2, actively detunable, coaxial birdcage coils to give homogeneous transmit, combined with a double resonant 30 channel receive array. This allows for anatomical imaging combined with 31P acquisitions over the whole head, without changing coils or disturbing the subject. A phosphate buffer phantom and 3 healthy volunteers were scanned with a pulse acquire CSI sequence using both the novel array coil and a conventional transceiver birdcage. Four different methods of combining the array channels were compared at 3 different levels of SNR. Results: The novel coil setup delivers significantly increased 31P SNR in the peripheral regions of the brain, reaching up to factor 8, while maintaining comparable performance relative to the birdcage in the center. Conclusions: The new system offers the potential to acquire whole brain 31P MRSI with superior signal relative to the standard options

Spectroscopie proton du cerveau humain à 3T : Imagerie spectroscopique volumétrique spirale à TE court

Proton MR chemical shift imaging (CSI) can identify biomarkers relevant to healthy or metabolic cerebral metabolism. At short TE, strongly J-coupled and short T2 metabolites can be detected. High field increases SNR and spectral resolution with the disadvantage of increased B1 and B0 heterogeneities as well as chemical shift displacement error (CSDE). Semi-LASER sequence reduces CSDE and B1 heterogeneity effects with improved slice selection profiles. Phase encoding CSI has long acquisition time. Spiral Spectroscopic Imaging (SSI) reduces minimum acquisition time. It becomes possible to acquire additional data such as a spatial dimension and/or a second spectral dimension. We developed a volumetric SSI of the human brain with a 17ms TE using PRESS with conventional RF pulses and with 32ms TE using semi-LASER combined with adapted water suppression and OVS modules. We implemented the trajectory measurement and 2D spatial - 1D spectral reconstruction programs. We observed good saturation of subcutaneous lipids. We obtained sharper selection profiles and reduced CSDE with adiabatic than conventional RF pulses. Using the measured trajectory for data reconstruction suppressed gradient hardware imperfections artefacts. With PRESS and semi-LASER selection modules, NAA, Cr, Cho, and myo-Inositol were significantly quantified. We have demonstrated in vivo short TE volumetric SSI acquisition at 3T using conventional and adiabatic refocusing pulses in a total acquisition time compatible with clinical examination. Further works need to be realised to optimise semi-LASER sequence for the detection of strongly coupled metabolite like glutamate and glutamine.L'imagerie spectroscopique (IS) par résonance magnétique nucléaire du cerveau permet d'identifier les biomarqueurs du métabolisme cérébral sain ou pathologique. A court TE, les métabolites ayant des couplages J forts et des temps de relaxation T2 courts peuvent être détectées. Le rapport signal sur bruit et la résolution spectrale croît avec l'intensité du champ B0. Cependant, l'hétérogénéité des champs B0 et B1 ainsi que les erreurs associées au déplacement chimique augmentent avec B0. De bons profils de sélection sont obtenus avec le module de sélection du volume d'intérêt de type semi-LASER comparés à ceux obtenus avec des impulsions conventionnelles. De plus, cette séquence est mois sensible aux hétérogénéités du champ B1 et les erreurs liées au déplacement chimique sont moins importantes. La limitation la plus contraignante de la technique d'imagerie spectroscopique conventionnelle est probablement sa longue durée d'acquisition qui dépend de la résolution spatiale. L'imagerie spectroscopique spirale (ISS) en encodant simultanément l'information spatiale et spectrale réduit considérablement le temps d'acquisition minimum. Il devient ainsi possible d'acquérir des données supplémentaires telles qu'une dimension spatiale et/ou une deuxième dimension spectrale. Nous avons mis en place une technique d'imagerie spectroscopique spirale pour l'étude du cerveau humain. Le TE est de 17 ms dans le cas de sélection du volume d'intérêt avec le module PRESS utilisant des impulsions RF conventionnelles et de 32 ms dans le cas de semi-LASER. Ces modules de sélection ont été combinés avec des modules de saturation des signaux de l'eau et du volume externe adaptés. Nous avons développé les programmes de calcul de la trajectoire mesurée et de la reconstruction des données à deux dimensions spatiales et une dimension spectrale. Nous avons obtenu une bonne saturation des lipides extracrâniens. Nous avons obtenu de meilleurs profils et une nette réduction des erreurs associées au déplacement chimique avec le module semi-LASER comparé avec ceux obtenus avec le module PRESS. L'application de la trajectoire mesurée à la reconstruction des données réduit les artefacts associés aux imperfections du système de gradients. Sur les spectres acquis à un TE de 17 ms (PRESS) et de 32 ms (semi-LASER) nous avons quantifié significativement le NAA, la choline, la créatine et le myo-inositol. Nous avons démontré la faisabilité de l'acquisition de données d'imagerie spectroscopique spirale volumétrique à TE court chez l'homme à 3T en une durée compatible avec celle des examens cliniques. D'autres travaux doivent être réalisés afin d'optimiser la séquence semi-LASER pour la détection de métabolites fortement couplés, comme le glutamate et la glutamine

Title: in vivo short TE localized 1 H MR spectroscopy of mouse cervical spinal cord at very high magnetic field (11.75T)

International audienceMR spectroscopy allows a noninvasive assessment of metabolic information in healthy and pathological central nervous system. Whereas MR spectroscopy has been extensively applied in the brain, only few spectroscopic studies of the spinal cord (SC) have been performed so far. For mice, due to additional technical challenges, in vivo 1H SC MRS has not yet been reported. In this work, the feasibility of short echo time localized proton magnetic resonance spectroscopy using Point RESolved Spectroscopy sequence for the examination of mouse cervical SC at 11.75 T is presented. Several optimizations were performed to improve the static field homogeneity, to reduce physiological motion effects and lipid contaminations arising from SC surrounding tissues, and to provide a careful metabolic quantification. Satisfactory spectrum quality was obtained. The described protocol allowed reliable quantification of five metabolites in the cervical SC. The mean reproducibility regarding the quantification of tNAA, tCr and tCho was ≥ 80%, > 70% for mI and > 55% for Glu, whereas the intersubject variabilities were ≤ 21%. The application of this protocol to transgenic mouse models in pathological conditions such as SC injury or neurodegenerative diseases may thus provide complementary information to MRI and increase our understanding of such pathologies

Vessel size index measurements in a rat model of glioma: comparison of the dynamic (Gd) and steady-state (iron-oxide) susceptibility contrast MRI approaches.

International audienceVessel size index (VSI), a parameter related to the distribution of vessel diameters, may be estimated using two MRI approaches: (i) dynamic susceptibility contrast (DSC) MRI following the injection of a bolus of Gd-chelate. This technique is routinely applied in the clinic to assess intracranial tissue perfusion in patients; (ii) steady-state susceptibility contrast with USPIO contrast agents, which is considered here as the standard method. Such agents are not available for human yet and the steady-state approach is currently limited to animal studies. The aim is to compare VSI estimates obtained with these two approaches on rats bearing C6 glioma (n = 7). In a first session, VSI was estimated from two consecutive injections of Gd-Chelate (Gd(1) and Gd(2)). In a second session (4 hours later), VSI was estimated using USPIO. Our findings indicate that both approaches yield comparable VSI estimates both in contralateral (VSI{USPIO} = 7.5 ± 2.0 µm, VSI{Gd(1)} = 6.5 ± 0.7 µm) and in brain tumour tissues (VSI{USPIO} = 19.4 ± 7.1 µm, VSI{Gd(1)} = 16.6 ± 4.5 µm). We also observed that, in the presence of BBB leakage (as it occurs typically in brain tumours), applying a preload of Gd-chelate improves the VSI estimate with the DSC approach both in contralateral (VSI{Gd(2)} = 7.1 ± 0.4 µm) and in brain tumour tissues (VSI{Gd(2)} = 18.5 ± 4.3 µm) but is not mandatory. VSI estimates do not appear to be sensitive to T(1) changes related to Gd extravasation. These results suggest that robust VSI estimates may be obtained in patients at 3 T or higher magnetic fields with the DSC approach

Whole brain 31P MRSI at 7T with a dual-tuned receive array

Purpose: The design and performance of a novel head coil setup for (Formula presented.) P spectroscopy at ultra-high field strengths (7T) is presented. The described system supports measurements at both the (Formula presented.) H and (Formula presented.) P resonance frequencies. Methods: The novel coil consists of 2, actively detunable, coaxial birdcage coils to give homogeneous transmit, combined with a double resonant 30 channel receive array. This allows for anatomical imaging combined with (Formula presented.) P acquisitions over the whole head, without changing coils or disturbing the subject. A phosphate buffer phantom and 3 healthy volunteers were scanned with a pulse acquire CSI sequence using both the novel array coil and a conventional transceiver birdcage. Four different methods of combining the array channels were compared at 3 different levels of SNR. Results: The novel coil setup delivers significantly increased (Formula presented.) P SNR in the peripheral regions of the brain, reaching up to factor 8, while maintaining comparable performance relative to the birdcage in the center. Conclusions: The new system offers the potential to acquire whole brain (Formula presented.) P MRSI with superior signal relative to the standard options

Whole brain P MRSI at 7T with a dual‐tuned receive array

Purpose: The design and performance of a novel head coil setup for 31P spectroscopy at ultra‐high field strengths (7T) is presented. The described system supports measurements at both the 1H and 31P resonance frequencies. Methods: The novel coil consists of 2, actively detunable, coaxial birdcage coils to give homogeneous transmit, combined with a double resonant 30 channel receive array. This allows for anatomical imaging combined with 31P acquisitions over the whole head, without changing coils or disturbing the subject. A phosphate buffer phantom and 3 healthy volunteers were scanned with a pulse acquire CSI sequence using both the novel array coil and a conventional transceiver birdcage. Four different methods of combining the array channels were compared at 3 different levels of SNR. Results: The novel coil setup delivers significantly increased 31P SNR in the peripheral regions of the brain, reaching up to factor 8, while maintaining comparable performance relative to the birdcage in the center. Conclusions: The new system offers the potential to acquire whole brain 31P MRSI with superior signal relative to the standard options

7,8-dihydroxyflavone enhances long-term spatial memory and alters brain volume in wildtype mice

Introduction: 7,8-dihydroxyflavone (7,8-DHF) is a low molecular weight compound that can cross the blood brain barrier and has been implicated in numerous functions and behaviours. It is thought to have neuroprotective capability and has been shown to alleviate symptoms in a wide range of diseases.Methods: 7,8-DHF was administered systemically to wildtype mice during Morris water maze training. Long-term spatial memory was assessed 28 days later. Ex-vivo T2-weighted (T2w) imaging was undertaken on a subset of these mice to assess brain-wide changes in volume.Results: We found that systemic 7,8-DHF administration during the training period enhanced spatial memory 28 days later. Volumetric changes were observed in numerous brain regions associated with a broad range of functions including cognition, sensory, and motor processing.Discussion: Our findings give the first whole brain overview of long-term anatomical changes following 7,8-DHF administration providing valuable information for assessing and understanding the widespread effects this drug has been shown to have in behaviour and disease