Magnetic resonance diffusion tensor imaging and tractography of the lower spinal cord: application to diastematomyelia and tethered cord

Cervical Diastematomyelia: A Case Presentation and Systematic Review

Diastematomyelia is a rare congenital disorder characterized by the separation of the spinal cord by an osseocartilaginous or fibrous septum. While diastematomyelia has been reported to be more common in the thoracic and lumbar regions, the true incidence of cervical diastematomyelia is currently unknown. In this study, we conducted the most comprehensive systematic review to date of all other case reports of diastematomyelia to better characterize the incidence of cervical diastematomyelia and provide comprehensive statistics on the clinical characteristics of diastematomyelia generally. Ninety-one articles were included in our study, which comprised 252 males (27.9%) and 651 females (72.0%) (and one patient with unspecified gender). In 507 cases, the vertebral level of the diastematomyelia was described, and we recorded those levels as either cervical ( n  = 8, 1.6%), thoracic ( n  = 220, 43.4%), lumbar ( n  = 277, 54.6%), or sacral ( n  = 2, 0.4%). In 719 cases, the type of diastematomyelia was specified as either Type I ( n  = 482, 67.0%) or Type II ( n  = 237, 33.0%). Our study found that diastematomyelia has been reported in the cervical region in only 1.6% of cases, and we provide comprehensive data that this disorder occurs in female-to-male ratio of approximately 2.6:1 and Type I versus Type II diastematomyelia in an estimated ratio of 2:1.

Reducing decompression levels by diffusion tensor imaging and conventional magnetic resonance imaging in degenerative lumbar spinal stenosis

BACKGROUND

The selection of a correct level in lumbar spinal stenosis (LSS) remains a common problem and is critically important to the effectiveness of this surgical treatment. Surgery is invasive, and extended laminectomy may lead to secondary surgical complications. The application of diffuse tensor imagining (DTI) and paraspinal mapping (PM) in addition to conventional magnetic resonance imaging (cMRI) may be helpful in this respect. However, the superiority of cMRI + DTI over cMRI+ (DTI or PM) in reducing decompression has not yet been established.

METHODS

We compared the surgical levels, determined by cMRI + DTI and cMRI+ (DTI or PM) (self-control). Treatment outcome measurements were performed at two weeks, three months, six months, and twelve months postoperatively.

RESULTS

The surgical levels determined by cMRI ± DTI showed less than that determined by cMRI± (DTI or PM) with statistically significant differences (p value = 0.0199) and cMRI ± PM with no statistically significant differences (p value = 0.5503).

CONCLUSIONS

The effectiveness of cMRI ± DTI in the reduction of the surgical levels in degenerative lumbar spinal stenosis is superior than that of cMRI± (DTI or PM).

Full cervical cord tractography: A new method for clinical use

Despite recent improvements in diffusion-weighted imaging, spinal cord tractography is not used in routine clinical practice because of difficulties in reconstructing tractograms, with a pertinent tri-dimensional-rendering, in a long post-processing time. We propose a new full tractography approach to the cervical spinal cord without extensive manual filtering or multiple regions of interest seeding that could help neurosurgeons manage various spinal cord disorders. Four healthy volunteers and two patients with either cervical intramedullary tumors or spinal cord injuries were included. Diffusion-weighted images of the cervical spinal cord were acquired using a Philips 3 Tesla machine, 32 diffusion directions, 1,000 s/mm²b-value, 2 × 2 × 2 mm voxel size, reduced field-of-view (ZOOM), with two opposing phase-encoding directions. Distortion corrections were then achieved using the FSL software package, and tracking of the full cervical spinal cord was performed using the DSI Studio software (quantitative anisotropy-based deterministic algorithm). A unique region of avoidance was used to exclude everything that is not of the nervous system. Fiber tracking parameters used adaptative fractional anisotropy from 0.015 to 0.045, fiber length from 10 to 1,000 mm, and angular threshold of 90°. In all participants, a full cervical cord tractography was performed from the medulla to the C7 spine level. On a ventral view, the junction between the medulla and spinal cord was identified with its pyramidal bulging, and by an invagination corresponding to the median ventral sulcus. On a dorsal view, the fourth ventricle—superior, middle, and inferior cerebellar peduncles—was seen, as well as its floor and the obex; and gracile and cuneate tracts were recognized on each side of the dorsal median sulcus. In the case of the intramedullary tumor or spinal cord injury, the spinal tracts were seen to be displaced, and this helped to adjust the neurosurgical strategy. This new full tractography approach simplifies the tractography pipeline and provides a reliable 3D-rendering of the spinal cord that could help to adjust the neurosurgical strategy.

Effect of distortion corrections on the tractography quality in spinal cord diffusion-weighted imaging

PURPOSE

To assess the impact of a different distortion correction (DC) method and patient geometry (sagittal balance) on the quality of spinal cord tractography rendering according to different tractography approaches.

METHODS

Forty-four adults free of spinal cord diseases underwent cervical diffusion-weighted imaging. The phase-encoding direction was head→foot. Sequence with opposed polarities (foot→head) was acquired to perform DC. Eddy-current, motion effects, and susceptibility artifact correction methods were used for DC, and two deterministic and one probabilistic tractography approaches were evaluated using MRtrix and DSI Studio tractography software. Fiber length and number of fibers were extracted to evaluate the quality of the tractography rendering. For each subject, cervical lordosis was measured to assess patient geometry. The angle between the main direction of the spinal cord and the orientation of the acquisition box were computed at each spine level to assess acquisition geometry and define an angle threshold for which a tractography of good quality is no longer possible.

RESULTS

There was a significant improvement in tractography quality after performing DC with susceptibility artifact correction using a deterministic approach based on tensor. Before DC, the angle threshold was defined at C6 (15.2°) compared with C7 (21.9°) after corrections, demonstrating the importance of spinal cord angulation for DC.

CONCLUSION

The impact of DC on tractography quality is greatly impacted by acquisition geometry. To obtain a good-quality tractography, we propose as a future perspective to adapt the acquisition geometry to that of the patient by automatically adjusting the acquisition box.

Update in the evaluation of peripheral nerves by MRI, from morphological to functional neurography

Imaging studies of peripheral nerves have increased considerably in the last ten years. In addition to the classical and still valid study by ultrasound, new neurographic techniques developed from conventional morphological sequences (including 3D isotropic studies with fat suppression) are making it possible to assess different peripheral nerves and plexuses, including small sensory and/or motor branches, with great precision. Diffusion-weighted sequences and diffusion tensor imaging have opened a new horizon in neurographic studies. This new approach provides morphological and functional information about the internal structure and pathophysiology of the peripheral nerves and diseases that involve them. This update reviews the different MR neurography techniques available for the study of the peripheral nerves, with special emphasis on new sequences based on diffusion.

Relationship between the benefits of paraspinal mapping and diffusion tensor imaging and the increase of decompression levels determined by conventional magnetic resonance imaging in degenerative lumbar spinal stenosis

BACKGROUND

In lumbar spinal stenosis (LSS), at most times, several levels are impaired and selecting the correct level remains a common problem for surgeons, as surgery remains invasive, and extended laminectomy may lead to secondary surgical complications. Therefore, helping to select the correct level may be useful for surgeons. The use of diffuse tensor imaging (DTI) and paraspinal mapping (PM) in addition to conventional magnetic resonance imaging (MRI) may be helpful (Chen et al., J Orthop Surg Res 11:47, 2016). However, with decompression levels determined by conventional magnetic resonance imaging (MRI) increasing, whether the benefits of reducing decompression level of conventional MRI + (DTI or PM) will be more obvious is unknown.

METHODS

Reduced surgical levels that were different between levels determined by conventional MRI + (DTI or PM) and conventional MRI + neurogenic examination (NE) between groups were compared. Treatment outcome measures were performed at 2 weeks, 3 months, 6 months, and 12 months postoperatively.

RESULTS

The reduced levels of three groups showed no statistically significant differences between each other except for two levels and four levels (two levels/three levels, p = 0.085; two levels/four levels, p = 0.039; three levels/ four levels, p = 0.506, respectively).

CONCLUSIONS

With surgical levels determined by conventional MRI increasing, the benefits of DTI and PM will be uncertainly more obvious.

Diffusion tensor imaging (DTI) and Tractography of the spinal cord in pediatric population with spinal lipomas: preliminary study

PURPOSE

Diffusion tensor imaging (DTI) allows studying the micro and macro architecture. One of the major challenges in dysraphism is to know the morphologic organization of the spinal cord. In a preliminary work, spinal lipoma was chosen for analyzing the micro-architecture parameters and fiber morphology of the spinal cord by DTI with tractography.

METHODS

Twelve patients (0-8 years) related to spinal lipomas treated between May 2017 and March 2018 were included. Tractography reconstruction of the conus medullaris of 12 patients were obtained using the MedINRIA software. The diffusion parameters have been calculated by Osirix DTImap plugin.

RESULTS

We found a significant difference in the FA (p = 0.024) between two age groups (< 24 months old and > 24 months old). However, no significant differences in the mean values of FA, RD, and MD between the level of the lipoma and the level above were noted. The tractography obtained in each case was coherent with morphologic sequences and reproducible. The conus medullaris was deformed and shifted. Destruction or disorganization of fibers and any passing inside the lipomas was not observed.

CONCLUSIONS

Tractography of the conus medullaris in a very young pediatric population (0-8 years old) with a spinal lipoma is possible, reproductive, and allows visualization of the spinal cord within the dysraphism. Analysis of the FA shows that the presence of a lipoma seems to have an effect on the myelination of the conus medullaris. It is during the probable myelination phase that the majority of symptoms appear. Is the myelination per se the cause?

Recent advances in magnetic resonance neuroimaging of lumbar nerve to clinical applications: A review of clinical studies utilizing Diffusion Tensor Imaging and Diffusion-weighted magnetic resonance neurography

Much progress has been made in neuroimaging with Magnetic Resonance neurography and Diffusion Tensor Imaging (DTI) owing to higher magnetic fields and improvements in pulse sequence technology. Reports on lumbar nerve DTI have also increased considerably. Many studies have shown that the use of DTI in lumbar nerve lesions, such as lumbar foraminal stenosis and lumbar disc herniation, makes it possible to capture images of interruptions of tractography at stenotic sties, enabling the diagnosis of stenosis. DTI can also reveal significant decreases in fractional anisotropy (FA) with significant increases in apparent diffusion coefficient (ADC) values in compression lesions. FA values have higher accuracy than ADC values. Furthermore, strong correlations exist between FA values and indications of neurological severity, including the Japanese Orthopedic Association (JOA) score, the Oswestry Disability Index (ODI), and the Roland-Morris Disability Questionnaire (RDQ) in patients with lumbar disc herniation-induced radiculopathy. Most lumbar DTI has become 3T; 3T MRI has made it possible to take high-resolution DTI measurements in a short period of time. However, increased motion artifacts in the magnetic susceptibility effect lead to signal irregularities and image distortion. In the future, high-resolution DTI with reduced field-of-view may become useful in clinical applications, since visualization of nerve lesions and quantification of DTI parameters could allow more accurate diagnoses of lumbar nerve dysfunctions. Future translational studies will be necessary to successfully bring MR neuroimaging of lumbar nerve into clinical use.

Enough positive rate of paraspinal mapping and diffusion tensor imaging with levels which should be decompressed in lumbar spinal stenosis

INTRODUCTION

In lumbar spinal stenosis, correlating symptoms and physical examination findings with decompression levels based on common imaging is not reliable. Paraspinal mapping (PM) and diffusion tensor imaging (DTI) may be possible to prevent the false positive occurrences with MRI and show clear benefits to reduce the decompression levels of lumbar spinal stenosis than conventional magnetic resonance imaging (MRI) + neurogenic examination (NE). However, they must have enough positive rate with levels which should be decompressed at first. The study aimed to confirm that the positive of DTI and PM is enough in levels which should be decompressed in lumbar spinal stenosis.

MATERIALS AND METHODS

The study analyzed the positive of DTI and PM as well as compared the preoperation scores to the postoperation scores, which were assessed preoperatively and at 2 weeks, 3 months 6 months, and 12 months postoperatively.

RESULTS

96 patients underwent the single level decompression surgery. The positive rate among PM, DTI, and (PM or DTI) was 76%, 98%, 100%, respectively. All post-operative Oswestry Disability Index (ODI), visual analog scale for back pain (VAS-BP) and visual analog scale for leg pain (VAS-LP) scores at 2 weeks postoperatively were measured improvement than the preoperative ODI, VAS-BP and VAS-LP scores with statistically significance (p-value = 0.000, p-value = 0.000, p-value = 0.000, respectively).

CONCLUSIONS

In degenetive lumbar spinal stenosis, the positive rate of (DTI or PM) is enough in levels which should be decompressed, thence using the PM and DTI to determine decompression levels will not miss the level which should be operated.

[Surgical treatment outcomes in children with tethered spinal cord syndrome. A prognosis on the basis of spinal 3T MRI tractography]

AIM

The study objective was to identify factors affecting surgical treatment outcomes in children with tethered cord syndrome (TCS).

MATERIAL AND METHODS

The study included 21 TCS patients aged 1 to 14 years who underwent tethered cord release. The preoperative and postoperative data of clinical and neurophysiological examination and high field (3T) MRI tractography of the caudal spinal cord were compared.

RESULTS

Regression of the TCS clinical and electrophysiological signs and the lack of pathological changes in the spinal cord tracts were observed in patients with filum terminale abnormalities and caudal lipomas after surgery. In patients with secondary spinal cord tethering caused by scar formation after lumbosacral myelomeningocele repair, a motor deficit was related to the interruption level of the spinal tracts, and surgical treatment did not lead to significant regression of the TCS clinical and electrophysiological signs.

CONCLUSION

We consider the absence of pathological changes in the caudal spinal cord, based on spinal MRI tractography, as a favorable prognostic factor in TCS surgical treatment.

Reducing surgical levels by paraspinal mapping and diffusion tensor imaging techniques in lumbar spinal stenosis

BACKGROUND

Correlating symptoms and physical examination findings with surgical levels based on common imaging results is not reliable. In patients who have no concordance between radiological and clinical symptoms, the surgical levels determined by conventional magnetic resonance imaging (MRI) and neurogenic examination (NE) may lead to a more extensive surgery and significant complications. We aimed to confirm that whether the use of diffusion tensor imaging (DTI) and paraspinal mapping (PM) techniques can further prevent the occurrence of false positives with conventional MRI, distinguish which are clinically relevant from levels of cauda equina and/or nerve root lesions based on MRI, and determine and reduce the decompression levels of lumbar spinal stenosis than MRI + NE, while ensuring or improving surgical outcomes.

METHODS

We compared the data between patients who underwent MRI + (PM or DTI) and patients who underwent conventional MRI + NE to determine levels of decompression for the treatment of lumbar spinal stenosis. Outcome measures were assessed at 2 weeks, 3 months, 6 months, and 12 months postoperatively.

RESULTS

One hundred fourteen patients (59 in the control group, 54 in the experimental group) underwent decompression. The levels of decompression determined by MRI + (PM or DTI) in the experimental group were significantly less than that determined by MRI + NE in the control group (p = 0.000). The surgical time, blood loss, and surgical transfusion were significantly less in the experimental group (p = 0.001, p = 0.011, p = 0.001, respectively). There were no differences in improvement of the visual analog scale back and leg pain (VAS-BP, VAS-LP) scores and Oswestry Disability Index (ODI) scores at 2 weeks, 3 months, 6 months, and 12 months after operation between the experimental and control groups.

CONCLUSIONS

MRI + (PM or DTI) showed clear benefits in determining decompression levels of lumbar spinal stenosis than MRI + NE. In patients with lumbar spinal stenosis, the use of PM and DTI techniques reduces decompression levels and increases safety and benefits of surgery.

Possibility Study of Scale Invariant Feature Transform (SIFT) Algorithm Application to Spine Magnetic Resonance Imaging

The purpose of this study is an application of scale invariant feature transform (SIFT) algorithm to stitch the cervical-thoracic-lumbar (C-T-L) spine magnetic resonance (MR) images to provide a view of the entire spine in a single image. All MR images were acquired with fast spin echo (FSE) pulse sequence using two MR scanners (1.5 T and 3.0 T). The stitching procedures for each part of spine MR image were performed and implemented on a graphic user interface (GUI) configuration. Moreover, the stitching process is performed in two categories; manual point-to-point (mPTP) selection that performed by user specified corresponding matching points, and automated point-to-point (aPTP) selection that performed by SIFT algorithm. The stitched images using SIFT algorithm showed fine registered results and quantitatively acquired values also indicated little errors compared with commercially mounted stitching algorithm in MRI systems. Our study presented a preliminary validation of the SIFT algorithm application to MRI spine images, and the results indicated that the proposed approach can be performed well for the improvement of diagnosis. We believe that our approach can be helpful for the clinical application and extension of other medical imaging modalities for image stitching.

Changes in lumbosacral spinal nerve roots on diffusion tensor imaging in spinal stenosis

Lumbosacral degenerative disc disease is a common cause of lower back and leg pain. Conventional T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) scans are commonly used to image spinal cord degeneration. However, these modalities are unable to image the entire lumbosacral spinal nerve roots. Thus, in the present study, we assessed the potential of diffusion tensor imaging (DTI) for quantitative assessment of compressed lumbosacral spinal nerve roots. Subjects were 20 young healthy volunteers and 31 patients with lumbosacral stenosis. T2WI showed that the residual dural sac area was less than two-thirds that of the corresponding normal area in patients from L₃ to S₁ stenosis. On T1WI and T2WI, 74 lumbosacral spinal nerve roots from 31 patients showed compression changes. DTI showed thinning and distortion in 36 lumbosacral spinal nerve roots (49%) and abruption in 17 lumbosacral spinal nerve roots (23%). Moreover, fractional anisotropy values were reduced in the lumbosacral spinal nerve roots of patients with lumbosacral stenosis. These findings suggest that DTI can objectively and quantitatively evaluate the severity of lumbosacral spinal nerve root compression.

3.0T MRI tractography of lumbar nerve roots in disc herniation

BACKGROUND

Diffusion tensor imaging (DTI) with fiber tracking (FT) has found clinical applications in the evaluation of the central nervous system and has been extensively used to image white matter tract. The feasibility of FT of the lumbar nerve roots in disc herniation is unclear.

PURPOSE

To demonstrate the feasibility of FT in the lumbar nerve roots, and to assess potential differences in fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of L4, L5, and S1 nerves between healthy disc and disc herniation.

MATERIAL AND METHODS

Twenty patients with unilateral sciatica related to posterolateral or foraminal disc herniation and 20 healthy volunteers were enrolled in our study. Anatomical fusion with the axial T2 sequences was used to estimate the relevance of reconstructions. DTI with tractography of the L4, L5, and S1 nerves was performed. Mean FA and ADC values were calculated from tractography images.

RESULTS

Lumbosacral root compression sites could be clearly identified on the tractography images. There was no significant difference in FA or ADC between left and right nerve roots at the same level (P > 0.05) in healthy volunteers. The mean FA value of the compressed spinal nerve roots was significantly lower than that of FA of the contralateral nerve roots (P = 0.0001). ADC was significantly higher in compressed nerve roots than that in the contralateral nerve root (P = 0.0002).

CONCLUSION

3 T magnetic resonance imaging (MRI) DTI and FT of the lumbosacral region nerve is possible. There are significant changes in FA and ADC values in the compressed L4, L5, and S1 nerves.

Clinical relevance of diffusion tensor imaging parameters in lumbar disco-radicular conflict

PURPOSE

To measure the fractional anisotropy (FA) and the mean diffusivity (MD) values of L4, L5 and S1 nerve roots using diffusion tensor imaging (DTI) and to correlate them with four different clinical patterns.

PATIENTS AND METHODS

Fifty-six human participants were prospectively included and divided between four groups: healthy subjects, patients with clinical symptomatic nerve root pain with and without anatomical discoradicular conflict and patients with incidental anatomical discoradicular conflict seen on magnetic resonance imaging (MRI). MRI protocol included anatomical sequences (sagittal T1- and T2-weighted, axial T2-weighted) and a 25 directions DTI sequence. FA and MD values were measured in consensus by two readers and compared between the four groups.

RESULTS

Mean FA and MD values were significantly different for patients with clinically symptomatic nerve root pain (n=27) both with (n=16) (FA=0.187±0.015; MD=510±40) and without (n=11) (FA=0.193±0.011; MD=490±30.5) anatomical discoradicular conflict compared to healthy subjects (n=29) (FA=0.221±0.011; MD=460.9±35.5) including 2 subjects with incidental anatomical discoradicular conflict (FA=0.211±0.013; MD=450.8±41.2) on MRI (P=0.003).

CONCLUSION

Measurement of FA and MD values of L4, L5 and S1 nerve roots using DTI could be useful in lumbar nerve root pain assessment. Further studies with different image processing methods are needed.

Diffusion-tensor imaging of small nerve bundles: cranial nerves, peripheral nerves, distal spinal cord, and lumbar nerve roots--clinical applications

OBJECTIVE

The purpose of this article is to review recent advances in diffusion-tensor imaging (DTI) and tractography of the cranial and peripheral nerves.

CONCLUSION

Advances in MR data acquisition and postprocessing methods are permitting high-resolution DTI of the cranial and peripheral nerves in the clinical setting. DTI offers information beyond routine clinical MRI, and DTI findings have implications for the diagnosis and treatment of nerve disease.

Recurrent tethered cord: radiological investigation and management

INTRODUCTION

Recurrent tethered cord (RTC) is almost the rule after the repair of myelomeningocele and quite frequent after the repair of lipomyelomeningocele, resulting from the adhesions of the placode within a too narrow spinal canal. About one-third of patients with myelomeningocele and 10 % of those with spinal lipoma develop symptomatic RTC, mainly caused by the ischemic-metabolic injuries due to the cord stretching. The goal of this review is to provide information about the pathophysiology, the radiological picture, and the management of RTV according to the pertinent literature and the authors' experience.

RADIOLOGICAL INVESTIGATION

The magnetic resonance imaging (MRI) picture is characterized by a low position of the conus and by tethering of the spinal cord to the subcutaneous scar or to the inner surface of the spinal canal. The radiological work-up always includes brain MRI, to rule out other possible causes of late neurological deterioration (as shunt malfunction), and MRI of the whole spinal cord, to detect possible associated lesions (syringomyelia, dermoids, etc.). X-rays and/or computed tomography scan of the spine is required for the assessment of scoliosis or other bony malformations.

MANAGEMENT

The surgical treatment is planned after a multidisciplinary neurological, urological, orthopedic, physiatric, and radiological evaluation. The surgical detethering is carried out cautiously, possibly with electrophysiological intraoperative monitoring. Surgery ensures improvement or stability of the clinical picture in 70-80 % of cases, the remaining 20-30 % of patients needing multiple operations for their recovery. Complications may affect up to one-third of operated patients, being mainly represented by CSF leak, pseudomeningocele, and shunt malfunction.

Parallel MR imaging

Parallel imaging is a robust method for accelerating the acquisition of magnetic resonance imaging (MRI) data, and has made possible many new applications of MR imaging. Parallel imaging works by acquiring a reduced amount of k-space data with an array of receiver coils. These undersampled data can be acquired more quickly, but the undersampling leads to aliased images. One of several parallel imaging algorithms can then be used to reconstruct artifact-free images from either the aliased images (SENSE-type reconstruction) or from the undersampled data (GRAPPA-type reconstruction). The advantages of parallel imaging in a clinical setting include faster image acquisition, which can be used, for instance, to shorten breath-hold times resulting in fewer motion-corrupted examinations. In this article the basic concepts behind parallel imaging are introduced. The relationship between undersampling and aliasing is discussed and two commonly used parallel imaging methods, SENSE and GRAPPA, are explained in detail. Examples of artifacts arising from parallel imaging are shown and ways to detect and mitigate these artifacts are described. Finally, several current applications of parallel imaging are presented and recent advancements and promising research in parallel imaging are briefly reviewed.

Fully automatic stitching of diffusion tensor images in spinal cord

Diffusion tensor imaging (DTI) has become an important tool for studying the spinal cord pathologies. To enable high resolution imaging for modern studies, the DTI technique utilizes a small field of view (FOV) to capture partial human spinal cords. However, normal aging and many other diseases which affect the entire spinal cord increase the desire of acquiring the continuous full-view of the spinal cord. To overcome this problem, this paper presents a novel pipeline for automatic stitching of three-dimensional (3D) DTI of different portions of the spinal cord. The proposed technique consists of two operations, e.g. feature-based registration and adaptive composition to stitch every source image together to create a panoramic image. In the feature-based registration process, feature points are detected from the apparent diffusion coefficient map, and then a novel feature descriptor is designed to characterize feature points directly from a tensor neighborhood. 3D affine transforms are achieved by determining the correspondence matching. In the adaptive composition process, an effective feathering approach is presented to compute the tensors in the overlap region by the Log-Euclidean metrics. We evaluate the algorithm on real datasets from one healthy subject and one adolescent idiopathic scoliosis (AIS) patient. The colored FA maps and fiber tracking results show the effectiveness and accuracy of the proposed stitching framework.

Fast diffusion tensor imaging and tractography of the whole cervical spinal cord using point spread function corrected echo planar imaging

Diffusion tensor imaging has been used in a number of spinal cord studies, but severe distortions caused by susceptibility induced field inhomogeneities limit its applicability to investigate small volumes within acceptable acquisition times. A way to evaluate image distortions is to map the point spread function of the voxel intensity in a reference scan. In this study, the point spread function was mapped for an echo-planar imaging sequence in the human cervical spinal cord with isotropic resolution and large field of view. Correction with the point spread function map improved anatomical consistency, and full cervical tractography was thereby possible from a C1 seed region in healthy controls and one individual with spinal cord injury. It is suggested that point spread function mapping of the spinal cord can be used in combination with sequence-based methods for reduction of susceptibility artifacts or in high-field imaging settings where off-resonance effects are pronounced.

Olfactory ensheathing cells from the nose: clinical application in human spinal cord injuries

Olfactory mucosa, the sense organ of smell, is an adult tissue that is regenerated and repaired throughout life to maintain the integrity of the sense of smell. When the sensory neurons of the olfactory epithelium die they are replaced by proliferation of stem cells and their axons grow from the nose to brain assisted by olfactory ensheathing cells located in the lamina propria beneath the sensory epithelium. When transplanted into the site of traumatic spinal cord injury in rat, olfactory lamina propria or purified olfactory ensheathing cells promote behavioural recovery and assist regrowth of some nerves in the spinal cord. A Phase I clinical trial demonstrated that autologous olfactory ensheathing cell transplantation is safe, with no adverse outcomes recorded for three years following transplantation. Autologous olfactory mucosa transplantation is also being investigated in traumatic spinal cord injury although this whole tissue contains many cells in addition to olfactory ensheathing cells, including stem cells. If olfactory ensheathing cells are proven therapeutic for human spinal cord injury there are several important practical issues that will need to be solved before they reach general clinical application. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.