Spatial normalization, bulk motion correction and coregistration for functional magnetic resonance imaging of the human cervical spinal cord and brainstem.
ABSTRACT Functional magnetic resonance imaging (fMRI) of the cortex is a powerful tool for neuroscience research, and its use has been extended into the brainstem and spinal cord as well. However, there are significant technical challenges with extrapolating the developments that have been achieved in the cortex to their use in the brainstem and spinal cord. Here, we develop a normalized coordinate system for the cervical spinal cord and brainstem, demonstrating a semiautomated method for spatially normalizing and coregistering fMRI data from these regions. fMRI data from 24 experiments in eight volunteers are normalized and combined to create the first anatomical reference volume, and based on this volume, we define a standardized region-of-interest (ROI) mask, as well as a map of 52 anatomical regions, which can be applied automatically to fMRI results. The normalization is demonstrated to have an accuracy of less than 2 mm in 93% of anatomical test points. The reverse of the normalization procedure is also demonstrated for automatic alignment of the standardized ROI mask and region-label map with fMRI data in its original (unnormalized) format. A reliable method for spatially normalizing fMRI data is essential for analyses of group data and for assessing the effects of spinal cord injury or disease on an individual basis by comparing with results from healthy subjects.
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ABSTRACT: PurposeTo assess and characterize responses to innocuous/noxious thermal stimuli and heat allodynia using functional spinal magnetic resonance imaging (spinal fMRI).Materials and Methods Spinal/supraspinal activation patterns of 16 healthy subjects were investigated by applying painful and nonpainful heat stimuli to dermatome C6 baseline and after sensitization with the heat/capsaicin model using fMRI (3T, single-shot TSE, TR 9000 msec, TE 38 msec, FOV 288 × 144 × 20 mm, matrix 192 × 96, voxel size 1 × 1 × 2 mm).ResultsIncreased activity was observed in ipsi- and contralateral ventral and dorsal spinal horn during noxious heat and heat allodynia. During noxious heat, but not during heat allodynia, activations were visible in the periaqueductal gray, ipsilateral cuneiform nucleus, and ipsilateral dorsolateral pontine tegmentum (DLPT). However, during heat allodynia activations were observed in bilateral ruber nuclei, contralateral DLPT, and rostral ventromedial medulla oblongata (RVM). Activations in contralateral subnucleus reticularis dorsalis (SRD) were visible during both noxious heat and heat allodynia (T >2.5, P < 0.01 for all of the above). After sensitization, activations in RVM and SRD correlated with activations in the ipsilateral dorsal horn of the spinal cord (R = 0.52–0.98, P < 0.05).Conclusion Spinal fMRI successfully demonstrates increased spinal activity and secondary changes in activation of supraspinal centers involved in pain modulation caused by peripheral nociceptor sensitization.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.Journal of Magnetic Resonance Imaging 04/2014; · 2.57 Impact Factor
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ABSTRACT: Mechanical hyperalgesia is one distressing symptom of neuropathic pain which is explained by central sensitization of the nociceptive system. This sensitization can be induced experimentally with the heat/capsaicin sensitization model. The aim was to investigate and compare spinal and supraspinal activation patterns of identical mechanical stimulation before and after sensitization using functional spinal magnetic resonance imaging (spinal fMRI). Sixteen healthy subjects (6 female, 10 male, mean age 27.2±4.0 years) were investigated with mechanical stimulation of the C6 dermatome of the right forearm during spinal fMRI. Testing was always performed in the area outside of capsaicin application (i.e. area of secondary mechanical hyperalgesia). During slightly noxious mechanical stimulation before sensitization, activity was observed in ipsilateral dorsolateral pontine tegmentum (DLPT) which correlated with activity in ipsilateral spinal cord dorsal gray matter (dGM) suggesting activation of descending nociceptive inhibition. During secondary mechanical hyperalgesia, decreased activity was observed in bilateral DLPT, ipsilateral/midline rostral ventromedial medulla (RVM), and contralateral subnucleus reticularis dorsalis, which correlated with activity in ipsilateral dGM. Comparison of voxel-based activation patterns during mechanical stimulation before/after sensitization showed deactivations in RVM and activations in superficial ipsilateral dGM. This study revealed increased spinal activity and decreased activity in supraspinal centers involved in pain modulation (SRD, RVM, DLPT) during secondary mechanical hyperalgesia suggesting facilitation of nociception via decreased endogenous inhibition. Results should help prioritize approaches for further in vivo studies on pain processing and modulation in humans.PLoS ONE 11/2014; 9(11):e112325. · 3.53 Impact Factor
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ABSTRACT: Patient and physiological motion can cause artifacts in DTI of the spinal cord which can impact image quality and diffusion indices. The purpose of this investigation was to determine a reliable motion correction method for pediatric spinal cord DTI and show effects of motion correction on DTI parameters in healthy subjects and patients with spinal cord injury. Ten healthy subjects and ten subjects with spinal cord injury were scanned using a 3 T scanner. Images were acquired with an inner field-of-view DTI sequence covering cervical spine levels C1 to C7. Images were corrected for motion using two types of transformation (rigid and affine) and three cost functions. Corrected images and transformations were examined qualitatively and quantitatively using in-house developed code. Fractional anisotropy (FA) and mean diffusivity (MD) indices were calculated and tested for statistical significance pre- and post- motion correction. Images corrected using rigid methods showed improvements in image quality, while affine methods frequently showed residual distortions in corrected images. Blinded evaluation of pre and post correction images showed significant improvement in cord homogeneity and edge conspicuity in corrected images (p < 0.0001). The average FA changes were statistically significant (p < 0.0001) in the spinal cord injury group, while healthy subjects showed less FA change and were not significant. In both healthy subjects and subjects with spinal cord injury, quantitative and qualitative analysis showed the rigid scaled-least-squares registration technique to be the most reliable and effective in improving image quality.Magnetic Resonance Imaging 06/2014; · 2.02 Impact Factor