High-fidelity diffusion tensor imaging of the cervical spinal cord using point-spread-function encoded EPI.

Diffusion tensor imaging (DTI) of the spinal cord is technically challenging due to the size of its structure and susceptibility-induced field inhomogeneity, which impedes clinical applications. This study aimed to achieve high-fidelity spinal cord DTI with reasonable SNR and practical acquisition efficiency. Particularly, a distortion-free multi-shot EPI technique, namely point-spread-function encoded EPI (PSF-EPI), was adopted for diffusion imaging of the cervical spinal cord (CSC). The shot number can be reduced to six for sagittal scans through titled-CAIPI acceleration and partial Fourier undersampling, consequently rendering this technique beneficial in clinics. Fifteen healthy volunteers and seven patients with metallic implants underwent sagittal scans using tilted-CAIPI PSF-EPI at 3T. Unsuppressed fat signals were further removed by retrospective water/fat separation using the intrinsic chemical-shift encoded signals. Compared with multi-shot interleaved EPI method, highly accelerated PSF-EPI method provided evidently improved distortion reduction and higher consistency with anatomical references even with metallic implants. Additionally, axial DTI scans using PSF-EPI were also evaluated quantitatively, and the measured DTI metrics are similar to those obtained from the zonal oblique multi-slice EPI (ZOOM-EPI) method and reported values. The high anatomical consistency, practical scan time and quantitative reliability indicate PSF-EPI's clinical potential for CSC diffusion imaging.

Assessing the spatial distribution of cervical spinal cord activity during tactile stimulation of the upper extremity in humans with functional magnetic resonance imaging.

Dermatomal maps are a mainstay of clinical practice and provide information on the spatial distribution of the cutaneous innervation of spinal nerves. Dermatomal deficits can help isolate the level of spinal nerve root involvement in spinal conditions and guide clinicians in diagnosis and treatment. Dermatomal maps, however, have limitations, and the spatial distribution of spinal cord sensory activity in humans remains to be quantitatively assessed. Here we used spinal cord functional MRI to map and quantitatively compare the spatial distribution of sensory spinal cord activity during tactile stimulation of the left and right lateral shoulders (i.e. C5 dermatome) and dorsal third digits of the hands (i.e., C7 dermatome) in healthy humans (n â€‹= â€‹24, age â€‹= â€‹36.8 â€‹± â€‹11.8 years). Based on the central sites for processing of innocuous tactile sensory information, we hypothesized that the activity would be localized more to the ipsilateral dorsal spinal cord with the lateral shoulder stimulation activity being localized more superiorly than the dorsal third digit. The findings demonstrate lateralization of the activity with the left- and right-sided stimuli having more activation in the ipsilateral hemicord. Contradictory to our hypotheses, the activity for both stimulation sites was spread across the dorsal and ventral hemicords and did not demonstrate a clear superior-inferior localization. Instead, the activity for both stimuli had a broader than expected distribution, extending across the C5, C6, and C7 spinal cord segments. We highlight the complexity of the human spinal cord neuroanatomy and several sources of variability that may explain the observed patterns of activity. While the findings were not completely consistent with our a priori hypotheses, this study provides a foundation for continued work and is an important step towards developing normative quantitative spinal cord measures of sensory function, which may become useful objective MRI-based biomarkers of neurological injury and improve the management of spinal disorders.

Cervical Canal Morphology: Effects of Neck Flexion in Normal Condition: New Elements for Biomechanical Simulations and Surgical Management.

STUDY DESIGN: Continuous measurements and computation of absolute metrics of cervical subarachnoid space (CSS) and spinal cord (SC) geometries proposed are based on in vivo magnetic resonance imaging and 3D reconstruction. OBJECTIVE: The aim of the study is to offer a new methodology to continuously characterize and to quantify the detailed morphology of the CSS and the cervical SC in 3D for healthy subjects in both neutral supine and flexion. SUMMARY OF BACKGROUND DATA: To the best of our knowledge, no study provides a morphological quantification by absolute indices based on the 3D reconstruction of SC and CSS thanks to in vivo magnetic resonance imaging. Moreover, no study provides a continuous description of the geometries. METHODS: Absolute indices of SC (cross-sectional area, compression ratio, position in the canal, length) and of CSS (cross-sectional area, occupational ratio, lengths) were computed by measures from 3D semi-automatic reconstructions of high resolution in vivo magnetic resonance images (3D T2-SPACE sequence) on healthy subjects (N = 11) for two postures: supine neutral and flexion neck positions. The variability induced by the semi-automatic reconstruction and by the landmarks positioning were investigated by preliminary sensitivity analyses. Inter and intra-variability were also quantified on a randomly chosen part of our population (N = 5). RESULTS: The length and cross-sectional area of SC are significantly different (P < 0.05) in flexion compared with neutral neck position. Spinal cord stays centered in the canal for both postures. However, the cross-sectional area of CSS is submitted to low variation after C3 vertebra for both postures. Occupational ratio (OR) and compression ratio (CR) after C3 are significantly lower in flexion. CONCLUSION: This study presented interpretations of morphological measures: (1) left-right stability (described by the Left-Right eccentricity index) ensured by the denticulate ligaments and the nerve roots attached to the dural sheaths, (2) a Poisson effect of the SC was partially notified through its axial (antero-posterior [AP] diameter, OR, CR) and its longitudinal geometrical descriptions (length of spinal cord [LSC]). Such morphological data can be useful for geometrical finite element modeling and could now be used to compare with injured or symptomatic subjects. LEVEL OF EVIDENCE: 3.

Considerations for Mean Upper Cervical Cord Area Implementation in a Longitudinal MRI Setting: Methods, Interrater Reliability, and MRI Quality Control.

BACKGROUND AND PURPOSE: Spinal cord atrophy is commonly measured from cerebral MRIs, including the upper cervical cord. However, rescan intraparticipant measures have not been investigated in healthy cohorts. This study investigated technical and rescan variability in the mean upper cervical cord area calculated from T1-weighted cerebral MRIs. MATERIALS AND METHODS: In this retrospective study, 8 healthy participants were scanned and rescanned with non-distortion- and distortion-corrected MPRAGE sequences (11-50 sessions in 6-8 months), and 50 participants were scanned once with distortion-corrected MPRAGE sequences in the Day2day daily variability study. From another real-world observational cohort, we collected non-distortion-corrected MPRAGE scans from 27 healthy participants (annually for 2-4 years) and cross-sectionally from 77 participants. Statistical analyses included coefficient of variation, smallest real difference, intraclass correlation coefficient, Bland-Altman limits of agreement, and paired t tests. RESULTS: Distortion- versus non-distortion-corrected MPRAGE-derived mean upper cervical cord areas were similar; however, a paired t test showed incomparability (t = 11.0, P = <.001). Higher variability was found in the mean upper cervical cord areas calculated from an automatic segmentation method. Interrater analysis yielded incomparable measures in the same participant scans (t = 4.5, P = <.001). Non-distortion-corrected mean upper cervical cord area measures were shown to be robust in real-world data (t = -1.04, P = .31). The main sources of variability were found to be artifacts from movement, head/neck positioning, and/or metal implants. CONCLUSIONS: Technical variability in cord measures decreased using non-distortion-corrected MRIs, a semiautomatic segmentation approach, and 1 rater. Rescan variability was within ±4.4% for group mean upper cervical cord area when MR imaging quality criteria were met.

Magnetic Resonance Imaging Atlas-Based Volumetric Mapping of the Cervical Cord Gray Matter in Cervical Canal Stenosis.

BACKGROUND: White matter volume loss may be an anatomic driver in the development of clinical symptoms in cervical spondylotic myelopathy (CSM). Considerably less attention has been devoted to gray matter (GM) injury. Newly developed atlas-based mapping techniques may allow evaluation of GM cord volume alterations in CSM. METHODS: There were 29 subjects evaluated: 15 patients with CSM (61.1 ± 8.7 years old) and 14 age-matched control subjects (56.1 ± 5.3 years old). All subjects underwent 3T magnetic resonance imaging of the cervical spine. Post-processing with the Spinal Cord Toolbox (v3.0) provided GM volumetric analysis. Clinical scores collected included modified Japanese Orthopaedic Association, neck and arm numeric rating scales, Nurick Scale, and Neck Disability Index. All volumes were normalized to account for anatomic variability. RESULTS: Normalized mean ventral GM volume in the compression region was significantly lower in patients compared with control subjects (1.103 ± 0.21 vs. 1.35 ± 0.32, P = 0.027). Normalized mean dorsal volume in the compression region was decreased in patients compared with control subjects (0.90 ± 0.17 vs. 1.04 ± 0.15, P = 0.049). GM volumes were associated with clinical scores, including Neck Disability Index, arm numeric rating scale, modified Japanese Orthopaedic Association, and Nurick Scale scores (P = 0.022, P = 0.004, P = 0.027, and P = 0.016). CONCLUSIONS: GM volume loss may be evaluated through atlas-based post-processing techniques and may correlate with clinical symptoms in CSM.

Anterior fissure, central canal, posterior septum and more: New insights into the cervical spinal cord gray and white matter regional organization using T1 mapping at 7T.

T1 mapping lacks specificity toward a single particular biological feature, however it has the potential to discriminate spinal cord regional tissue organization and characterize tissue microstructural impairments occurring in neurodegenerative pathologies. In this exploratory work, T1 mapping of the cervical spinal cord with a 300-µm in-plane resolution was performed on fourteen healthy subjects at 7T, using the MP2RAGE sequence. Individual images from C1 to C7 vertebral levels provided a clear delineation of spinal cord anatomical details and substructures including motor columns within gray matter (GM) horns, anterior median fissure, central canal, ventral, lateral and dorsal white matter (WM) fasciculi, and posterior median septum. Group studies highlighted regional T1 differences between regions of interest so far hardly visible at lower spatial resolution. Two-dimensional averaged T1 maps and manual parcellation of GM and WM substructures were built based on these data. Benefiting from the very high spatial resolution achievable at ultra-high field for T1 mapping, this work contributes to improve the in vivo characterization of the cervical spinal cord. By allowing investigation within a wider range of functional regions, it also opens new perspectives for pathology diagnosis such as motor neuron disease, neuropathic pain or refined investigation of neurodegeneration.

Diffusion MRI microstructural models in the cervical spinal cord - Application, normative values, and correlations with histological analysis.

Multi-compartment tissue modeling using diffusion magnetic resonance imaging has proven valuable in the brain, offering novel indices sensitive to the tissue microstructural environment in vivo on clinical MRI scanners. However, application, characterization, and validation of these models in the spinal cord remain relatively under-studied. In this study, we apply a diffusion "signal" model (diffusion tensor imaging, DTI) and two commonly implemented "microstructural" models (neurite orientation dispersion and density imaging, NODDI; spherical mean technique, SMT) in the human cervical spinal cord of twenty-one healthy controls. We first provide normative values of DTI, SMT, and NODDI indices in a number of white matter ascending and descending pathways, as well as various gray matter regions. We then aim to validate the sensitivity and specificity of these diffusion-derived contrasts by relating these measures to indices of the tissue microenvironment provided by a histological template. We find that DTI indices are sensitive to a number of microstructural features, but lack specificity. The microstructural models also show sensitivity to a number of microstructure features; however, they do not capture the specific microstructural features explicitly modelled. Although often regarded as a simple extension of the brain in the central nervous system, it may be necessary to re-envision, or specifically adapt, diffusion microstructural models for application to the human spinal cord with clinically feasible acquisitions - specifically, adjusting, adapting, and re-validating the modeling as it relates to both theory (i.e. relevant biology, assumptions, and signal regimes) and parameter estimation (for example challenges of acquisition, artifacts, and processing).

Structural mapping with fiber tractography of the human cuneate fasciculus at microscopic resolution in cervical region.

Human spinal white matter tract anatomy has been mapped using post mortem histological information with the help of molecular tracing studies in animal models. This study used 7 Tesla diffusion MR tractography on a human cadaver that was harvested 24 hours post mortem to evaluate cuneate fasciculus anatomy in cervical spinal cord. Based on this method, for the first time much more nuanced tractographic anatomy was used to investigate possible new routes for cuneate fasciculus in the posterior and lateral funiculus. Additionally, current molecular tracing studies were reviewed, and confirmatory data was presented along with our radiological results. Both studies confirm that upon entry to the spinal cord, upper cervical level tracts (C1-2-3) travel inside lateral funiculus and lower level tracts travel medially inside the posterior funiculus after entry at posterolateral sulcus which is different than traditional knowledge of having cuneate fasciculus tracts concentrated in the lateral part of posterior funiculus.

Somatotopy and Organization of Spinothalamic Tracts in the Human Cervical Spinal Cord.

BACKGROUND: Understanding spinothalamic tract anatomy may improve lesioning and outcomes in patients undergoing percutaneous cordotomy. OBJECTIVE: To investigate somatotopy and anatomical organization of spinothalamic tracts in the human cervical spinal cord. METHODS: Patients with intractable cancer pain undergoing cordotomy underwent preoperative and postoperative quantitative sensory testing for sharp pain and heat pain on day 1 and 7 after cordotomy. Intraoperative sensory stimulation was performed with computed tomography (CT) imaging to confirm the location of the radiofrequency electrode during cordotomy. Postoperative magnetic resonance (MR) imaging was performed to define the location of the lesion. RESULTS: Twelve patients were studied, and intraoperative sensory stimulation combined with CT imaging revealed a somatotopy where fibers from the legs were posterolateral to fibers from the hand. Sharpness detection thresholds were significantly elevated in the area of maximum pain on postoperative day 1 (P = .01). Heat pain thresholds for all areas were not elevated significantly on postoperative day 1, or postoperative day 7. MR imaging confirmed that the cordotomy lesion was in the anterolateral quadrant, and in this location the lesion had a sustained effect on sharp pain but a transient impact on heat pain. CONCLUSION: In the high cervical spinal cord, spinothalamic fibers mediating sharp pain for the arms are located ventromedial to fibers for the legs, and these fibers are spatially distinct from fibers that mediate heat pain.

A morphometric and stereological study on cervical spinal cord segment of goose.

In this study, volume density of white matter and grey matter areas of cervical segment of spinal cord in adult geese weighing 3-4 kg was examined using stereological methods. 10 geese were used as material without sex discrimination. All animals underwent perfusion with 10% buffered formaldehyde. Following the perfusion, animals were kept in 10% formaldehyde for 1 week. Geese were then dissected. Cervical area of spinal cord was revealed removing cervical spine. Tissue samples were obtained from each segment of cervical area. 5 µm thick cross-sections were taken from these tissue samples via microtome. Series of cross-sections were obtained by sampling in the ratio of 1/250 including 12 cross-sections from each cervical segment of every animal. Cross-sections were stained by haematoxylin eosin. They were photographed under microscope. Volume density (volume fractions) of both whole tissue and white matter and grey matter parts in each cervical segment of spinal cord were calculated using Cavalieri's Principle. In the study, total volume of cervical segment, volume of white matter and grey matter, and ratios of these volumes one another were assessed in goose.

Spinal cord grey matter segmentation challenge.

An important image processing step in spinal cord magnetic resonance imaging is the ability to reliably and accurately segment grey and white matter for tissue specific analysis. There are several semi- or fully-automated segmentation methods for cervical cord cross-sectional area measurement with an excellent performance close or equal to the manual segmentation. However, grey matter segmentation is still challenging due to small cross-sectional size and shape, and active research is being conducted by several groups around the world in this field. Therefore a grey matter spinal cord segmentation challenge was organised to test different capabilities of various methods using the same multi-centre and multi-vendor dataset acquired with distinct 3D gradient-echo sequences. This challenge aimed to characterize the state-of-the-art in the field as well as identifying new opportunities for future improvements. Six different spinal cord grey matter segmentation methods developed independently by various research groups across the world and their performance were compared to manual segmentation outcomes, the present gold-standard. All algorithms provided good overall results for detecting the grey matter butterfly, albeit with variable performance in certain quality-of-segmentation metrics. The data have been made publicly available and the challenge web site remains open to new submissions. No modifications were introduced to any of the presented methods as a result of this challenge for the purposes of this publication.

Microsurgical Anatomy of the Hypoglossal and C1 Nerves: Description of a Previously Undescribed Branch to the Atlanto-Occipital Joint.

OBJECTIVE: Distal branches of the C1 nerve that travel with the hypoglossal nerve have been well investigated but relationships of C1 and the hypoglossal nerve near the skull base have not been described in detail. Therefore, the aim of this study was to investigate these small branches of the hypoglossal and first cervical nerves by anatomic dissection. METHODS: Twelve sides from 6 cadaveric specimens were used in this study. To elucidate the relationship among the hypoglossal, vagus, and first and cervical nerve, the mandible was removed and these nerves were dissected under the surgical microscope. RESULTS: A small branch was found to always arise from the dorsal aspect of the hypoglossal nerve at the level of the transverse process of the atlas and joined small branches from the first and second cervical nerves. The hypoglossal and C1 nerves formed a nerve plexus, which gave rise to branches to the rectus capitis anterior and rectus capitis lateralis muscles and the atlanto-occipital joint. CONCLUSIONS: Improved knowledge of such articular branches might aid in the diagnosis and treatment of patients with pain derived from the atlanto-occipital joint. We believe this to be the first description of a branch of the hypoglossal nerve being involved in the innervation of this joint.

Neurochemical profile of the human cervical spinal cord determined by MRS.

MRS enables insight into the chemical composition of central nervous system tissue. However, technical challenges degrade the data quality when applied to the human spinal cord. Therefore, to date detection of only the most prominent metabolite resonances has been reported in the healthy human spinal cord. The aim of this investigation is to provide an extended metabolic profile including neurotransmitters and antioxidants in addition to metabolites involved in the energy and membrane metabolism of the human cervical spinal cord in vivo. To achieve this, data quality was improved by using a custom-made, cervical detector array together with constructive averaging of a high number of echo signals, which is enabled by the metabolite cycling technique at 3T. In addition, the improved spinal cord spectra were extensively cross-validated, in vivo, post-mortem in situ and ex vivo. Reliable identification of up to nine metabolites was achieved in group analyses for the first time. Distinct features of the spinal cord neurochemical profile, in comparison with the brain neurotransmission system, include decreased concentrations of the sum of glutamate and glutamate and increased concentrations of aspartate, γ-amino-butyric acid, scyllo-inositol and the sum of myo-inositol and glycine.

High-resolution multi-parametric quantitative magnetic resonance imaging of the human cervical spinal cord at 7T.

Quantitative MRI techniques have the potential to characterize spinal cord tissue impairments occurring in various pathologies, from both microstructural and functional perspectives. By enabling very high image resolution and enhanced tissue contrast, ultra-high field imaging may offer further opportunities for such characterization. In this study, a multi-parametric high-resolution quantitative MRI protocol is proposed to characterize in vivo the human cervical spinal cord at 7T. Multi-parametric quantitative MRI acquizitions including T1, T2* relaxometry mapping and axial diffusion MRI were performed on ten healthy volunteers with a whole-body 7T system using a commercial prototype coil-array dedicated to cervical spinal cord imaging. Automatic cord segmentation and multi-parametric data registration to spinal cord templates enabled robust regional studies within atlas-based WM tracts and GM horns at the C3 cervical level. T1 value, cross-sectional area and GM/WM ratio evolutions along the cervical cord were also reported. An original correction method for B1+-biased T1 mapping sequence was additionally proposed and validated on phantom. As a result, relaxometry and diffusion parameters derived from high-resolution quantitative MRI acquizitions were reported at 7T for the first time. Obtained images, with unmatched resolutions compared to lower field investigations, provided exquisite anatomical details and clear delineation of the spinal cord substructures within an acquisition time of 30min, compatible with clinical investigations. Regional statistically significant differences were highlighted between WM and GM based on T1 and T2* maps (p<10-3), as well as between sensory and motor tracts based on diffusion tensor imaging maps (p<0.05). The proposed protocol demonstrates that ultra-high field spinal cord high-resolution quantitative MRI is feasible and lays the groundwork for future clinical investigations of degenerative spinal cord pathologies.

Relatively Large Cervical Spinal Cord for Spinal Canal is a Risk factor for Development of Cervical Spinal Cord Compression: A Cross-Sectional Study of 1211 Subjects.

STUDY DESIGN: A cross-sectional study. OBJECTIVE: This study aims to investigate the correlation of the cervical canal and spinal cord size, and evaluate whether the size of the spinal cord relative to the spinal canal is a risk factor for development of cervical spinal cord compression (SCC). SUMMARY OF BACKGROUND DATA: There is little knowledge regarding the relationship between cervical bony canal and spinal cord diameters. Although developmental canal stenosis has been recognized as a risk factor for SCC, the size of the spinal cord relative to the spinal canal has not been similarly discussed. METHODS: Cervical canal anteroposterior (AP) diameters on X-rays and AP diameters and cross-sectional areas of dural sacs and spinal cords on magnetic resonance imaging (MRI) were measured in 1211 healthy volunteers. Correlation between cervical canal diameter on X-rays and AP diameter and cross-sectional area of dural sacs and spinal cords on MRI were assessed. The ratio of the AP diameter of the spinal cord/dural sac was compared between subjects with and without SCC. RESULTS: Spinal canal diameters were not highly correlated with spinal cord AP diameters and cross-sectional areas, although spinal canal diameters were significantly correlated with dural sac AP diameters. The individual difference in the ratio of the AP diameter of the spinal cord/dural sac was large (35%-93%), and the ratio was significantly larger in the subjects with SCC. An AP diameter ratio more than 62% at the C2 to C3 disc level is a risk factor for developing SCC. CONCLUSION: The spinal cord diameter was independent of the spinal canal diameter and the relative size of a spinal cord and spinal canal differed on an individual basis. In addition, the ratio of spinal cord/dural sac in subjects with SCC was significantly larger. Therefore, a relatively large spinal cord could be a risk factor for SCC.

Normal values of cervical spinal cord diffusion tensor in young and middle-aged healthy Chinese.

PURPOSE: Lack of normal reference value of diffusion tensor imaging parameters hinders its application in clinical practice. In this study, we aim to establish a comprehensive normal DTI database of Chinese subjects. METHODS: Sixty-five healthy subjects aged 21-61 years were recruited and underwent 3T DTI scan of cervical spine. DTI parameters were measured in whole cord, ventral, lateral and dorsal column from C2 to C7 segments. Regions, segments, gender and age-related changes of DTI parameters were analyzed. RESULTS: No significant difference was found between genders (p > 0.05). DTI parameters significantly differed among different cord levels (p < 0.05). FA value in whole cord, grey matter, dorsal and ventral column showed significant but weak correlation with age (p < 0.05). CONCLUSION: A comprehensive normal database of DTI parameters of cervical spinal cord was established. The effect of gender and age-related changes is negligible in DTI analysis of cervical spinal cord disorders.

Diffusion imaging in the rat cervical spinal cord.

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a diagnostic and prognostic tool in cases of disease or injury. Diffusion weighted imaging (DWI), is sensitive to the thermal motion of water molecules and allows for inferences of tissue microstructure. This report describes a protocol to acquire and analyze DWI of the rat cervical spinal cord on a small-bore animal system. It demonstrates an imaging setup for the live anesthetized animal and recommends a DWI acquisition protocol for high-quality imaging, which includes stabilization of the cord and control of respiratory motion. Measurements with diffusion weighting along different directions and magnitudes (b-values) are used. Finally, several mathematical models of the resulting signal are used to derive maps of the diffusion processes within the spinal cord tissue that provide insight into the normal cord and can be used to monitor injury or disease processes noninvasively.

Anatomy and biomechanics of the craniovertebral junction.

The craniovertebral junction (CVJ) has unique anatomical structures that separate it from the subaxial cervical spine. In addition to housing vital neural and vascular structures, the majority of cranial flexion, extension, and axial rotation is accomplished at the CVJ. A complex combination of osseous and ligamentous supports allow for stability despite a large degree of motion. An understanding of anatomy and biomechanics is essential to effectively evaluate and address the various pathological processes that may affect this region. Therefore, the authors present an up-to-date narrative review of CVJ anatomy, normal and pathological biomechanics, and fixation techniques.

Neurite orientation dispersion and density imaging of the healthy cervical spinal cord in vivo.

Here we present the application of neurite orientation dispersion and density imaging (NODDI) to the healthy spinal cord in vivo. NODDI provides maps such as the intra-neurite tissue volume fraction (vin), the orientation dispersion index (ODI) and the isotropic volume fraction (viso), and here we investigate their potential for spinal cord imaging. We scanned five healthy volunteers, four of whom twice, on a 3T MRI system with a ZOOM-EPI sequence. In accordance to the published NODDI protocol, multiple b-shells were acquired at cervical level and both NODDI and diffusion tensor imaging (DTI) metrics were obtained and analysed to: i) characterise differences in grey and white matter (GM/WM); ii) assess the scan-rescan reproducibility of NODDI; iii) investigate the relationship between NODDI and DTI; and iv) compare the quality of fit of NODDI and DTI. Our results demonstrated that: i) anatomical features can be identified in NODDI maps, such as clear contrast between GM and WM in ODI; ii) the variabilities of vin and ODI are comparable to that of DTI and are driven by biological differences between subjects for ODI, have similar contribution from measurement errors and biological variation for vin, whereas viso shows higher variability, driven by measurement errors; iii) NODDI identifies potential sources contributing to DTI indices, as in the brain; and iv) NODDI outperforms DTI in terms of quality of fit. In conclusion, this work shows that NODDI is a useful model for in vivo diffusion MRI of the spinal cord, providing metrics closely related to tissue microstructure, in line with findings in the brain.

Structural imaging of the cervical spinal cord with suppressed CSF signal using DANTE pulse trains.

PURPOSE: We propose DANTE (Delays Alternating with Nutation for Tailored Excitation) moving fluid attenuation preparation pulse trains, in conjunction with T1 , T2 , and proton-density-weighted fast spin-echo (T1w-TSE, T2w-TSE and PDw-TSE) imaging readout, and three-dimensional fast low flip angle shots (3D-FLASH) T1 -weighted imaging readout to achieve CSF-suppressed high-spatial resolution multicontrast cervical spinal cord images. METHODS: DANTE pulse trains, consisting of a rapid series of low flip angle radiofrequency pulses interspersed with gradients, were used to substantially attenuate the longitudinal magnetization of flowing spins relative to static tissue/fluid, whose longitudinal magnetization is mostly preserved. We hypothesized that the contrast between spinal cord and cerebrospinal fluid (CSF) could be maximized due to moving CSF signal suppression. RESULTS: We demonstrate that metrics of contrast-to-noise ratio between spinal cord, nerve root, and CSF regions (CNRcord-CSF and CNRnerve-CSF ) are improved by at least a factor of 2 when compared with images acquired with non-prepared approaches and with 2D multiple-echo data image combination (MEDIC) imaging. In addition, we find that sagittal image quality can be significantly improved due to flow suppression effects from the DANTE preparation pluses. CONCLUSION: DANTE prepared imaging techniques for moving CSF signal attenuation are promising tools for cervical spinal cord imaging.