Diffusion Tensor Imaging of the Normal Cervical and Thoracic Pediatric Spinal Cord

A matched case-control study of early cervical spondylotic myelopathy based on diffusion magnetic resonance imaging

BACKGROUND

Early cervical spondylotic myelopathy (CSM) is challenging to diagnose and easily missed. Diffusion MRI (dMRI) has the potential to identify early CSM.

METHODS

Using diffusion tensor imaging (DTI), diffusion kurtosis imaging (DKI), and neurite orientation dispersion and density imaging (NODDI), a 1:1 matched case-control study was conducted to evaluate the potential of dMRI in identifying early CSM and assessing uncompressed segments of CSM patients. CSM patients and volunteers were matched by age and spinal location. The differences in dMRI parameters between groups were assessed by the paired t-test, the multicollinearity of the dMRI parameters was evaluated by the variance inflation factor (VIF), and the value of dMRI parameters in distinguishing controls from CSM patients was determined by logistic regression. The univariate t-test was used to analyse differences between CSM patients and volunteers in adjacent uncompressed areas.

RESULTS

In total, 56 CSM patients and 56 control volunteers were included. Paired t-tests revealed significant differences in nine dMRI parameters between groups. Multicollinearity calculated through VIF and combined with logistic regression showed that the orientation division index (ODI) was significantly positively correlated (r = 2.12, p = 0.035), and the anisotropic water fraction (AWF) was significantly negatively correlated (r = -0.98, p = 0.015). The fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), isotropic volume fraction (ISOVF), ODI, and AWF were significantly different in the upper and lower uncompressed areas at all ages.

CONCLUSION

dMRI can noninvasively identify early CSM patients and potentially identify the extent of CSM lesions involving the cervical spinal cord.

CRITICAL RELEVANCE STATEMENT

Diffusion MRI (dMRI) can identify early cervical spondylotic myelopathy (CSM) and has the potential to help determine the extent of CSM involvement. The application of dMRI can help screen for early CSM and develop clinical surgical and rehabilitation treatment plans.

KEY POINTS

• Diffusion MRI can differentiate between normal and early-stage cervical spondylotic myelopathy patients. • Diffusion MRI has the ability to identify the extent of spinal cord involvement in cervical spondylotic myelopathy. • Diffusion MRI enables the early screening of cervical spondylotic myelopathy and helps guide clinical treatment.

Correlations of diffusion tensor imaging and clinical measures with spinal cord cross-sectional area measurements in pediatric spinal cord injury patients

PURPOSE

The purpose of this work was to employ a semi-automatic method for measuring spinal cord cross-sectional area (SCCSA) and investigate the correlations between diffusion tensor imaging (DTI) metrics and SCCSA for the cervical and thoracic spinal cord for typically developing pediatric subjects and pediatric subject with spinal cord injury.

METHODS

Ten typically developing (TD) pediatric subjects and ten pediatric subjects with spinal cord injury (SCI) were imaged using a Siemens Verio 3 T MR scanner to acquire DTI and high-resolution anatomic scans covering the cervical and thoracic spinal cord (C1-T12). SCCSA was measured using a semi-automated edge detection algorithm for the entire spinal cord. DTI metrics were obtained from whole cord axial ROIs at each vertebral level. SCCSA measures were compared to DTI metrics by vertebral level throughout the entire cord, and above and below the injury site. Correlation analysis was performed to compare SCCSA, DTI and clinical measures as determined by the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) examination.

RESULTS

In subjects with SCI, FA and SCCSA had a positive correlation (r = 0.81, P < 0.01), while RD and SCCSA had a negative correlation (r = -0.68, P = 0.02) for the full spinal cord. FA and SCCSA were correlated above (r = 0.56, P < 0.01) and below (r = 0.54, P < 0.01) the injury site. TD subjects showed negative correlations between AD and SCCSA (r = -0.73, P = 0.01) and RD and SCCSA (r = -0.79, P < 0.01).

CONCLUSION

The ability to quickly and effectively measure SCCSA in subjects with SCI has the potential to allow for a better understanding of the progression of atrophy following a SCI. Correlations between cord cross section and DTI metrics by vertebral level suggest that imaging inferior and superior to lesion may yield useful information for diagnosis and prognosis.

Porcine Model of the Growing Spinal Cord-Changes in Diffusion Tensor Imaging Parameters

Diffusion tensor imaging (DTI) is an advanced magnetic resonance imaging (MRI) technique that has promising applications for the objective assessment of the microstructure of the spinal cord. This study aimed to verify the parameters obtained using DTI change during the growth process. We also wanted to identify if the DTI values change on the course of the spinal cord. The model organism was a healthy growing porcine spinal cord (19 pigs, Polish White, weight 24-120 kg, mean 48 kg, median 48 kg, age 2.5-11 months, mean 5 months, median 5.5 months). DTI parameters were measured in three weight groups: up to 29 kg (five pigs), 30-59 kg (six pigs), and from 60 kg up (eight pigs). DTI was performed with a 1.5 Tesla magnetic resonance scanner (Philips, Ingenia). Image post-processing was done using the Fiber Track package (Philips Ingenia workstation) by manually drawing the regions of interest (nine ROIs). The measurements were recorded for three sections: the cervical, thoracolumbar and lumbar segments of the spinal cord at the C4/C5, Th13/L1, and L4/L5 vertebrae levels. In each case, one segment was measured cranially and one caudally from the above-mentioned places. The values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were obtained for each ROIs and compared. It is shown that there is a correlation between age, weight gain, and change in FA and ADC parameters. Moreover, it is noted that, with increasing weight and age, the FA parameter increases and ADC decreases, whereas the FA and ADC measurement values did not significantly change between the three sections of the spinal cord. These findings could be useful in determining the reference values for the undamaged spinal cords of animals and growing humans.

Variation in Diffusion Tensor Imaging Parameters in the Cervical and Thoracic Spinal Cord (C1-C5 and C6-T2) Segments of Normal Beagle Dogs

This study aimed to determine the characteristics and reference values of each vertebra in the cervicothoracic region by performing diffusion tensor imaging (DTI) scans and analyzing DTI parameters in normal Beagle dogs. In five adult Beagles under anesthetic maintenance, DTI was performed using a 1.5-T magnetic resonance imaging (MRI) scanner. Axial DTI was performed using three overlapping slabs to cover the cervical and thoracic spinal cords. After post-processing, DTI parameters were calculated along the entire spinal cord. Among DTI parameters, fractional anisotropy, relative anisotropy, and axonal diffusivity significantly decreased in the caudal direction. However, the apparent diffusion coefficient, radial diffusivity, and mean diffusivity values were not significantly correlated with vertebral levels. We provide evidence for the existence of segment-dependent DTI parameters in the canine cervical spinal cord. Therefore, comparisons of DTI parameters between lesions at different vertebral levels should be avoided unless normative data are available. Furthermore, the DTI data obtained in this study may contribute to the development of a clinical reference for spinal cord evaluation in dogs using DTI parameters.

Diffusion Kurtosis Imaging of Neonatal Spinal Cord in Clinical Routine

Diffusion kurtosis imaging (DKI) has undisputed advantages over the more classical diffusion magnetic resonance imaging (dMRI) as witnessed by the fast-increasing number of clinical applications and software packages widely adopted in brain imaging. However, in the neonatal setting, DKI is still largely underutilized, in particular in spinal cord (SC) imaging, because of its inherently demanding technological requirements. Due to its extreme sensitivity to non-Gaussian diffusion, DKI proves particularly suitable for detecting complex, subtle, fast microstructural changes occurring in this area at this early and critical stage of development, which are not identifiable with only DTI. Given the multiplicity of congenital anomalies of the spinal canal, their crucial effect on later developmental outcome, and the close interconnection between the SC region and the brain above, managing to apply such a method to the neonatal cohort becomes of utmost importance. This study will (i) mention current methodological challenges associated with the application of advanced dMRI methods, like DKI, in early infancy, (ii) illustrate the first semi-automated pipeline built on Spinal Cord Toolbox for handling the DKI data of neonatal SC, from acquisition setting to estimation of diffusion measures, through accurate adjustment of processing algorithms customized for adult SC, and (iii) present results of its application in a pilot clinical case study. With the proposed pipeline, we preliminarily show that DKI is more sensitive than DTI-related measures to alterations caused by brain white matter injuries in the underlying cervical SC.

Clinical Utility of Diffusion Tensor Imaging as a Biomarker to Identify Microstructural Changes in Pediatric Spinal Cord Injury

Background

Lack of clarity about the neurological consequence of spinal cord injury (SCI) in children causes speculation about diagnoses, recovery potential, and treatment effectiveness. Diffusion tensor imaging (DTI) has shown promising results as a biomarker to evaluate spinal cord integrity at a microstructural level.

Objectives

To look at the difference between pediatric participants with and without SCI to determine which DTI metrics best categorize spinal cord tissue damage and to correlate DTI metrics with two clinical measures: Capabilities of the Upper Extremity Test (CUE-T) and Spinal Cord Independence Measure version III (SCIM-III).

Methods

This single-site, prospective study included pediatric participants with SCI (n = 26) and typically developed (TD) control subjects (n = 36). All participants underwent two magnetic resonance imaging (MRI) scans on a 3T MR scanner. Participants with SCI also completed the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), CUE-T, and SCIM-III outcomes measures.

Results

This study found significant strength of association between fractional anisotropy (FA) and upper extremity muscle strength (UEMS) in participants with SCI. Most DTI parameters showed a significant difference between participants with SCI and TD participants and a moderate correlation with the CUE-T total score. Regional effects on group differences were found to be significant.

Conclusion

This study demonstrates the strength of association between DTI parameters and clinical measures in the pedantic SCI population. It illustrates DTI as a potential biomarker of SCI location and severity in the pediatric SCI population.

Atlas-Based Quantification of DTI Measures in a Typically Developing Pediatric Spinal Cord

BACKGROUND AND PURPOSE

Multi-parametric MRI, provides a variety of biomarkers sensitive to white matter integrity, However, spinal cord MRI data in pediatrics is rare compared to adults. The purpose of this work was 3-fold: 1) to develop a processing pipeline for atlas-based generation of the typically developing pediatric spinal cord WM tracts, 2) to derive atlas-based normative values of the DTI indices for various WM pathways, and 3) to investigate age-related changes in the obtained normative DTI indices along the extracted tracts.

MATERIALS AND METHODS

DTI scans of 30 typically developing subjects (age range, 6-16 years) were acquired on a 3T MR imaging scanner. The data were registered to the PAM50 template in the Spinal Cord Toolbox. Next, the DTI indices for various WM regions were extracted at a single section centered at the C3 vertebral body in all the 30 subjects. Finally, an ANOVA test was performed to examine the effects of the following: 1) laterality, 2) functionality, and 3) age, with DTI-derived indices in 34 extracted WM regions.

RESULTS

A postprocessing pipeline was developed and validated to delineate pediatric spinal cord WM tracts. The results of ANOVA on fractional anisotropy values showed no effect for laterality (P = .72) but an effect for functionality (P < .001) when comparing the 30 primary WM labels. There was a significant (P < .05) effect of age and maturity of the left spinothalamic tract on mean diffusivity, radial diffusivity, and axial diffusivity values.

CONCLUSIONS

The proposed automated pipeline in this study incorporates unique postprocessing steps followed by template registration and quantification of DTI metrics using atlas-based regions. This method eliminates the need for manual ROI analysis of WM tracts and, therefore, increases the accuracy and speed of the measurements.

Cerebral White Matter Myelination and Relations to Age, Gender, and Cognition: A Selective Review

White matter makes up about fifty percent of the human brain. Maturation of white matter accompanies biological development and undergoes the most dramatic changes during childhood and adolescence. Despite the advances in neuroimaging techniques, controversy concerning spatial, and temporal patterns of myelination, as well as the degree to which the microstructural characteristics of white matter can vary in a healthy brain as a function of age, gender and cognitive abilities still exists. In a selective review we describe methods of assessing myelination and evaluate effects of age and gender in nine major fiber tracts, highlighting their role in higher-order cognitive functions. Our findings suggests that myelination indices vary by age, fiber tract, and hemisphere. Effects of gender were also identified, although some attribute differences to methodological factors or social and learning opportunities. Findings point to further directions of research that will improve our understanding of the complex myelination-behavior relation across development that may have implications for educational and clinical practice.

Specific microstructural changes of the cervical spinal cord in syringomyelia estimated by diffusion tensor imaging

The microstructure of the spinal cord in syringomyelia has not been well studied. The aim of this study was to evaluate the microstructure of the cervical cord in patients with syringomyelia using diffusion tensor imaging (DTI) and to investigate the association between DTI parameters and the size of the syrinx cavity. Thirty patients with syringomyelia and 11 age-matched controls were included in this study. DTI and T1/T2-weighted MRI were used to estimate spinal microstructure. The patients were divided into a clinical symptom group (group A) and a non-clinical symptom group (group B) according to ASIA assessments. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values (mm²/s) were measured and compared between patients and controls. Correlation between FA/ADC and the size of the syrinx cavity was examined with a bivariate analysis. FA values were lower (P < 0.000) and ADC values were higher (P < 0.000) compared to the controls at the level of all syrinxes examined in patients with syringomyelia; both FA values and ADC values reached normal values either above or below the syrinx levels (all P > 0.05). FA values and ADC values at all cervical levels were not significantly different either in controls or outside of the syrinx (all P > 0.05). FA values of group A was significantly lower than those of group B (P < 0.000). There was a negative association between FA values and the size of syrinx cavity, and a positive association between ADC values and the size of syrinx cavity (FA: P < 0.05, ADC: P < 0.05). The microstructure of the cervical spinal cord is different across all patients with syringomyelia. DTI is a promising tool for estimating quantitative pathological characteristics that are not visible with general MRI.

Prospective Comparison of Reduced Field-of-View (rFOV) and Full FOV (fFOV) Diffusion-Weighted Imaging (DWI) in the Assessment of Insulinoma: Image Quality and Lesion Detection

RATIONALE AND OBJECTIVES

To prospectively compare the image quality (IQ) and lesion detection performance of reduced field-of-view (rFOV) and full FOV (fFOV) diffusion-weighted imaging (DWI) sequences in detecting insulinomas.

MATERIALS AND METHODS

From October 2017 to September 2018, 67 patients with suspected insulinomas were prospectively enrolled and underwent imaging with both types of DWI sequences. The slice thickness (4 mm) and slice gaps (1 mm) were the same for the two DWI sequences, and the TR/TE was 2235/56 ms for the rFOV sequence and 1892/63 ms for the fFOV sequence. Three radiologists independently assessed the imaging quality (IQ) subjectively with a 5-point scale and objectively with signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements. The IQ scores, CNR, SNR, lesion detection rates, and ADC values were compared. Receiver operating characteristic curves were generated, and the area under the curve (AUC) was used to compare the diagnostic performance.

RESULTS

Fifty patients were tumor positive, with 65 tumors (size: 1.31 ± 0.77 cm, range: 0.6-5.8 cm). The IQ score, SNR, and CNR were significantly higher for rFOV DWI than for fFOV DWI (IQ: 3.64 ± 0.487 vs 3.310 ± 0.577, SNR: 22.520 ± 8.690 vs 10.284 ± 3.321, CNR: 3.454 ± 2.642 vs 1.327 ± 2.801, and all p < 0.05). For lesions less than 1.5 cm (n = 55), the lesion detection rates of the rFOV were statistically improved compared to those of the fFOV (90.7% vs. 75.9%, p = 0.039). The sensitivity of lesion detection was significantly improved with the rFOV-DWI sequences compared to that with the fFOV-DWI sequences (0.924 vs. 0.773, p = 0.013). The ADC values of the two DWI sequences were consistent for insulinomas and normal parenchyma.

CONCLUSION

Considering the improvements in overall IQ and lesion detection and the consistency of ADC measurements, we suggest that rFOV DWI is a reliable auxiliary alternative to fFOV DWI for clinical practice in the detection of pancreatic insulinomas.

Magnetization transfer and diffusion tensor imaging in dogs with intervertebral disk herniation

Background

Quantitative magnetic resonance imaging (QMRI) techniques of magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) provide microstructural information about the spinal cord.

Objective

Compare neurologic grades using the modified Frankel scale with MTR and DTI measurements in dogs with thoracolumbar intervertebral disk herniation (IVDH).

Animals

Fifty‐one dogs with thoracolumbar IVDH.

Methods

Prospective cohort study. Quantitative MRI measurements of the spinal cord were obtained at the region of compression. A linear regression generalized estimating equations model was used to compare QMRI measurements between different neurological grades after adjusting for age, weight, duration of clinical signs, and lesion location.

Results

Grade 5 (.79  ×  10⁻³ mm²/s [median], .43−.91 [range]) and axial (1.47 × 10⁻³ mm²/s, .58−1.8) diffusivity were lower compared to grades 2 (1.003, .68−1.36; P = .02 and 1.81 × 10⁻³ mm²/s, 1.36−2.12; P < .001, respectively) and 3 (1.07 × 10⁻³ mm²/s, .77−1.5; P = .04 and 1.92 × 10⁻³ mm²/s, 1.83−2.37;P < .001, respectively). Compared to dogs with acute myelopathy, chronic myelopathy was associated with higher mean (1.02 × 10⁻³ mm²/s, .77−1.36 vs. .83 × 10⁻³ mm²/s, .64−1.5; P = .03) and radial diffusivity (.75 × 10⁻³ mm²/s, .38−1.04 vs. .44 × 10⁻³ mm²/s, .22−1.01; P = .008) and lower MTR (46.76, 31.8−56.43 vs. 54.4, 45.2−62.27; P = .004) and fractional anisotropy (.58, .4−0.75 vs. .7, .46−.85; P = .02). Fractional anisotropy was lower in dogs with a T2‐weighted intramedullary hyperintensity compared to those without (.7, .45−.85 vs. .54, .4−.8; P = .01).

Conclusion and Clinical Relevance

Mean diffusivity and AD could serve as surrogates of severity of spinal cord injury and are complementary to the clinical exam in dogs with thoracolumbar IVDH.

Microstructural Changes in Compressed Cervical Spinal Cord Are Consistent With Clinical Symptoms and Symptom Duration

STUDY DESIGN

A prospective study.

OBJECTIVE

To investigate the association between microstructural changes measured by diffusion tensor imaging (DTI) and clinical symptoms and their duration in patients with cervical spondylotic myelopathy (CSM) affected by single level.

SUMMARY OF BACKGROUND DATA

No report was reported regarding the association between the microstructural changes and the symptoms and their duration at single-level spinal cord compression.

METHODS

Twenty-nine consecutive patients with CSM and 29 normal subjects were enrolled in this study. DTI with tractography was performed on the cervical spinal cord. Clinical symptoms were evaluated using modified Japanese Orthopaedic Association (mJOA) scores for each patient, and the duration of clinical symptoms was noted based on the earliest instance of limb pain or numbness or weakness or bladder dysfunction. Mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were calculated from tractography images.

RESULTS

The mean FA value of the cervical compressed spinal cord was significantly lower than the FA of the normal population (P < 0.001). The mean ADC value in the cervical compressed spinal cord was obviously higher than those of normal cervical spinal cord (P < 0.001). In the CSM patients, a significant positive association was observed between FA values and mJOA scores (P < 0.001). However, there were a notable negative association between mJOA scores and ADC values (P < 0.001), and between mJOA scores and symptom duration (P < 0.001).

CONCLUSION

These results illustrate DTI can measure the micostructural changes of cervical spinal cord and DTI parameters are potential biomarkers for spinal cord dysfunction in patients with CSM.

LEVEL OF EVIDENCE

3.

Quantification of DTI in the Pediatric Spinal Cord: Application to Clinical Evaluation in a Healthy Patient Population

BACKGROUND AND PURPOSE

The purpose of the study is to characterize diffusion tensor imaging indices in the developing spinal cord, evaluating differences based on age and cord region. Describing the progression of DTI indices in the pediatric cord increases our understanding of spinal cord development.

MATERIALS AND METHODS

A retrospective analysis was performed on DTI acquired in 121 pediatric patients (mean, 8.6 years; range, 0.3-18.0 years) at Monroe Carell Jr. Children's Hospital at Vanderbilt from 2017 to 2018. Diffusion-weighted images (15 directions; b = 750 s/mm²; slice thickness, 5 mm; in-plane resolution, 1.0 × 1.0 mm²) were acquired on a 3T scanner in the cervicothoracic and/or thoracolumbar cord. Manual whole-cord segmentation was performed. Images were masked and further segmented into cervical, upper thoracic, thoracolumbar, and conus regions. Analyses of covariance were performed for each DTI-derived index to investigate how age affects diffusion across cord regions, and 95% confidence intervals were calculated across age for each derived index and region. Post hoc testing was performed to analyze regional differences.

RESULTS

Analyses of covariance revealed significant correlations of age with axial diffusivity, mean diffusivity, and fractional anisotropy (all, P < .001). There were also significant differences among cord regions for axial diffusivity, radial diffusivity, mean diffusivity, and fractional anisotropy (all, P < .001).

CONCLUSIONS

This research demonstrates that diffusion evolves in the pediatric spinal cord during development, dependent on both cord region and the diffusion index of interest. Future research could investigate how diffusion may be affected by common pediatric spinal pathologies.

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?

Diffusion Tensor Imaging Assessment of Regional White Matter Changes in the Cervical and Thoracic Spinal Cord in Pediatric Subjects

There are no studies to date,describing changes in the diffusion tensor imaging (DTI) metrics of the white matter (WM) regions of the entire cervical and thoracic spinal cord (SC) remote from the lesion in pediatric spinal cord injury (SCI) subjects. The purpose of this study was to determine whether DTI at sites cephalad and caudal to a lesion provides measures of cord abnormalities in children with chronic SCI. A retrospective study included 10 typically developing subjects (TD) and 10 subjects with chronic SCI who underwent SC imaging in 2014-2017. Axial diffusion tensor images using an inner field of view DTI sequence were acquired to cover the entire cervical and thoracic SC. Regions of interest were drawn on the SC WM: right and left lateral (motor), ventral (motor), and dorsal (sensory) tracts. To detect differences in DTI metrics between TD and SCI of the cord, a one way analysis of variance with pooled t test was performed. A stepwise regression analysis was performed to assess the correlation between DTI metrics and clinical scores. In motor and sensory tracts, fractional anisotropy (FA) and axial diffusivity (AD) were significantly decreased in the proximal segments of the caudal cord. In motor tracts cephalad to the lesion, FA was significantly decreased whereas AD was significantly increased in the proximal segment; however, AD was decreased in the distal and middle segments. International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) total score was significantly correlated with FA and AD of the motor and sensory tracts cephalad to the lesion. This study demonstrates that FA and AD have the potential to be sensitive biomarkers of the full extent of cord injury and might be useful in detecting remote injuries to the SC and in guiding new treatments.

Predictive value of flexion and extension diffusion tensor imaging in the early stage of cervical myelopathy

PURPOSE

Diffusion tensor imaging (DTI) in flexion (F) and extension (E) may serve as a sensitive diagnostic tool in early symptoms of myelopathy. The aim of this study was to compare values of water diffusion parameters on dynamic cervical DTI in early stage of myelopathy.

METHODS

Study enrolled 10 patients with an early stage of cervical myelopathy, in grade I/II of Nurick classification. All subjects were scanned with flexion-extension 3T MRI. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), RD (radial diffusivity), AD (axial diffusivity) and TRACEW (trace diffusion) were measured at C2, compression level (CL) and C7. Parameters were compared between 3 levels and F and E positions.

RESULTS

Flexion DTI revealed significant difference only for TRACEW between C2 and C7 (105.8 ± 18.9 vs. 83.7 ± 14, respectively; p = 0.0029). Extension DTI showed differences for ADC between CL and C7 (1378.9 ± 381.8 vs. 1227.2 ± 269.2; p = 0.001), reduced FA from 664.6 ± 56.3 at C2 down to 553.1 ± 75.5 (p = 0.001) at CL and 584.7 ± 40.7 at C7 (p = 0.002). Differences of RD in E were significant through all levels and reached 612.9 ± 105.1, 955.3 ± 319.4 and 802.1 ± 194.1 at C2, CL and C7, respectively. TRACEW lowered from 92.3 ± 14.4 at C2 to 66.9 ± 21.1 at CL (p = 0.0001) and 64.4 ± 15.5 at C7 (p = 0.0002). Comparison of DTI between F and E showed differences for all parameters except AD. RD was significantly higher in E at CL (p = 0.003) and C7 (0.013), but TRACEW increased in F at CL by 27.4% (p = 0.001) and at C7 by 23.1% (p = 0.013). FA was reduced at CL in E (p = 0.027) and similarly ADC in F (p = 0.048).

CONCLUSION

Dynamic DTI of the cervical spine is feasible and can detect subtle spinal cord damage of functional relevance in cervical myelopathy. A marked increase of RD and decrease of FA and TRACEW values in extension were found to be indicative for an early structural cord injury in myelopathy.

Zonally Magnified Oblique Multislice and Non-Zonally Magnified Oblique Multislice DWI of the Cervical Spinal Cord

BACKGROUND AND PURPOSE

The zonally magnified oblique multislice EPI (ZOOM-EPI) diffusion-weighted sequence has been visually shown to provide superior MR diffusion image quality compared with the full-FOV single-shot EPI sequence (non-ZOOM-EPI) in the adult cervical spinal cord. The purpose of this study was to examine the diffusion tensor imaging indices in the normal human cervical spinal cord between ZOOMED and non-ZOOMED DTI acquisitions and determine whether DTI values are comparable between direct and indirect age-matched groups.

MATERIALS AND METHODS

Fifty-four subjects 23-58 years of age (9 direct age-matched and 45 indirect age-matched) were scanned using a 1.5T scanner. Diffusion tensor indices including fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were generated from the DTI dataset. These DTI values were calculated for both ZOOM and non-ZOOM acquisitions and compared at each intervertebral disc level. The variability of the DTI values for ZOOM and non-ZOOM sequences was measured using a coefficient of variation within direct and indirect age-matched controls.

RESULTS

The mean diffusivity, axial diffusivity, and radial diffusivity values obtained along the cervical spinal cord in the age-matched controls showed a significant decrease using the ZOOM sequence (P = .05, P = .002, and P < .001). Mean fractional anisotropy showed a significant increase (P = .04) using the ZOOM sequence. The indirect age-matched controls showed a statistically significant increase in fractional anisotropy (P = .03) and a decrease in mean diffusivity (P = .002), axial diffusivity (P < .001), and radial diffusivity (P = .002) using the ZOOM sequence. Less variability has been shown in DTI using the ZOOM sequence compared with the non-ZOOM sequence in both direct and indirect age groups. The ZOOM sequence exhibited higher SNR (SNR_ZOOM = 22.84 ± 7.59) compared with the non-ZOOM sequence (SNR_non-ZOOM = 19.7 ± 7.05). However, when we used a 2-tailed t test assuming unequal variances, the ZOOM sequence did not demonstrate a statistically significant increase.

CONCLUSIONS

ZOOM DTI acquisition methods provide superior image quality and precision over non-ZOOM techniques and are recommended over conventional full-FOV single-shot EPI DTI for clinical applications in cervical spinal cord imaging.

Characterization of spinal cord diffusion tensor imaging metrics in clinically asymptomatic pediatric subjects with incidental congenital lesions

Study design

Retrospective study.

Objectives

To perform quantitative DTI measurements of the entire cervical and thoracic spinal cord (SC) in typically developing (TD) pediatric subjects with incidental findings of syringomyelia or hydromyelia on conventional MRI and in a TD population without any abnormalities.

Setting

USA.

Methods

26 TD recruited as part of large SC DTI study, four of these had incidental findings. Axial DTI images were acquired on 3T MR scanner to cover the cervical and thoracic SC. We performed group analysis of DTI values in the cord above and below the MR-defined lesion. For single-subject analysis, the cord above and below the lesion was compared to average values of TD population. A standard least squares regression model was used to compare DTI parameters fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) between TD population and subjects with hydromyelia and syringomyelia. A p value of 0.05 was used for statistical significance.

Results

In group analysis, MD and AD were significantly different in cord above the lesion in subjects with hydromyelia and syringomyelia (n = 4) compared to TD population (n = 22). For single-subject analysis, DTI parameters were significantly different in cord above the syringomyelia and below the syringomyelia; MD, AD, and RD were significantly different. A subject with hydromyelia showed significant difference in FA below the lesion.

Conclusions

This study demonstrates that DTI has the potential to be used as an imaging biomarker to evaluate SC above and below the congenital lesion in syringohydromyelia subjects.

Age related diffusion and tractography changes in typically developing pediatric cervical and thoracic spinal cord

Background and objective

Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) are two techniques that can measure white matter integrity of the spinal cord. Recently, DTI indices have been shown to change with age. The purpose of this study is (a) to evaluate the maturational states of the entire pediatric spinal cord using DTI and DTT indices including fractional anisotropy (FA), mean diffusivity (MD), mean length of white matter fiber tracts and tract density and (b) to analyze the DTI and DTT parameters along the entire spinal cord as a function of spinal cord levels and age.

Method

A total of 23 typically developing (TD) pediatric subjects ranging in age from 6 to 16 years old (11.94 ± 3.26 (mean ± standard deviation), 13 females and 10 males) were recruited, and scanned using 3.0 T MR scanner. Reduced FOV diffusion tensor images were acquired axially in the same anatomical location prescribed for the T2-weighted images to cover the entire spinal cord (C1-mid L1 levels). To mitigate motion induced artifacts, diffusion directional images were aligned with the reference image (b0) using a rigid body registration algorithm performed by in-house software developed in Matlab (MathWorks, Natick, Massachusetts). Diffusion tensor maps (FA and MD) and streamline deterministic tractography were then generated from the motion corrected DTI dataset. DTI and DTT parameters were calculated by using ROIs drawn to encapsulate the whole cord along the entire spinal cord by an independent board certified neuroradiologist. These indices then were compared between two age groups (age group A = 6-11 years (n = 11) and age group B = 12-16 years (n = 12)) based on similar standards and age definitions used for reporting spinal cord injury in the pediatric population. Standard least squared linear regression based on a restricted maximum likelihood (REML) method was used to evaluate the relationship between age and DTI and DTT parameters.

Results

An increase in FA (group A = 0.42 ± 0.097, group B = 0.49 ± 0.116), white matter tract density (group A = 368.01 ± 236.88, group B = 440.13 ± 245.24) and mean length of fiber tracts (group A = 48.16 ± 20.48 mm, group B = 60.28 ± 23.87 mm) and a decrease in MD (group A = 1.06 ± 0.23 × 10-3 mm2/s, group B = 0.82 ± 0.24 × 10-3 mm2/s) were observed with age along the entire spinal cord. Statistically significant increases have been shown in FA (p = 0.004, R2 = 0.57), tract density (p = 0.0004, R2 = 0.58), mean length of fiber tracts (p < 0.001, R2 = 0.5) and a significant decrease has been shown in MD (p = 0.002, R2 = 0.59) between group A and group B. Also, it has been shown DTI and DTT parameters vary along the spinal cord as a function of intervertebral disk and mid-vertebral body level.

Conclusion

This study provides an initial understanding of age related changes of DTI values as well as DTT metrics of the spinal cord. The results show significant differences in DTI and DTT parameters which may result from decreasing water content, myelination of fiber tracts, and the thickening diameter of fiber tracts during the maturation process. Consequently, when quantitative DTI and DTT of the spinal cord is undertaken in the pediatric population an age and level matched normative dataset should be used to accurately interpret the quantitative results.

Reduced Field of View Diffusion Tensor Imaging and Fiber Tractography of the Pediatric Cervical and Thoracic Spinal Cord Injury

The aim of this study is to assess the utility and effectiveness of diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) of the entire pediatric cervical and thoracic spinal cord toward discrimination of typically developing (TD) controls and subjects with spinal cord injury (SCI). A total of 43 pediatric subjects, including 23 TD subjects ranging in age from 6 to 16 years old and 20 subjects with SCI ranging in age from 7 to 16 years, were recruited and scanned using a 3.0 Tesla magnetic resonance scanner. Reduced field of view diffusion tensor images were acquired axially to cover the entire spinal cord across two slabs. For DTI analysis, motion correction was performed by coregistration of the diffusion-weighted images to the reference image (b0). Streamline deterministic tractography results were generated from the preprocessed data. DTI and DTT parameters of the whole cord, including fractional anisotropy (FA), mean diffusivity (MD), tract length, and tract density, were calculated, averaged across the whole spinal cord, and compared between the TD and SCI groups. Statistically significant decreases have been shown in FA (TD = 0.46 ± 0.11; SCI = 0.37 ± 0.09; p < 0.0001) and tract density (TD = 405.93 ± 243.84; SCI = 268.90 ± 270.34; p < 0.0001). However, the mean length of tracts and MD did not show significant differences. When investigating differences in DTI and DTT parameters above and below the injury site, it was shown that the FA and tract density in patients with cervical SCI decreased significantly in the thoracic region. An identical trend was observed in the cervical region for patients with thoracic SCI as well. When comparing TD and SCI subjects, FA and tract density were the most sensitive parameters in detecting functional changes of the spinal cord in chronic pediatric SCI. The results show that both DTI and DTT have the potential to be imaging biomarkers in the diagnosis of SCI.