Diffusion tensor imaging reveals brain structure changes in dogs after spinal cord injury

Based on the Wallerian degeneration in the spinal cord pathways,the changes in synaptic connections,and the spinal cord-related cellular responses that alter the cellular structure of the brain,we presumed that brain diffusion tensor imaging(DTI)parameters may change after spinal cord injury.However,the dynamic changes in DTI parameters remain unclear.We established a Beagle dog model of T10 spinal cord contusion and performed DTI of the injured spinal cord.We found dynamic changes in DTI parameters in the cerebral peduncle,posterior limb of the internal capsule,pre-and postcentral gyri of the brain within 12 weeks after spinal cord injury.We then performed immunohistochemistry to detect the expression of neurofilament heavy polypeptide(axonal marker),glial fibrillary acidic protein(glial cell marker),and NeuN(neuronal marker).We found that these pathological changes were consistent with DTI parameter changes.These findings suggest that DTI can display brain structure changes after spinal cord injury.

Diffusion tensor imaging of horizontal extraocular muscles in patients with concomitant and paralytic esotropia

AIM:To assess metrics of diffusion tensor imagining(DTI)in evaluating microstructural abnormalities of horizontal extraocular muscles(EOM)in esotropia.METHODS:Six adult concomitant esotropia patients,5 unilateral abducent paralysis patients and 2 healthy volunteers were enrolled.Conventional magnetic resonance imaging(MRI)and DTI were performed on all subjects using 3T MR scanner.Fractional anisotropy(FA),mean diffusivity(MD),axial diffusivity(AD),and radial diffusivity(RD)of medial and lateral rectus muscles were measured and compared between patients group and control group.RESULTS:Medial rectus MD and RD within the adducted eye of concomitant patients was significantly greater than that in unilateral abducent paralysis patients(0.259×10-2 mm^(2)/s vs 0.207×10-2 mm^(2)/s,P=0.014;0.182×10-2 mm^(2)/s vs 0.152×10-2 mm^(2)/s,P=0.017).Both strabismus patients showed a significantly decreased MD and AD than that obtained in normal controls for lateral rectus muscles(P<0.05).Medial rectus MD of the adducted eye in concomitant strabismus patients was significantly decreased than that in healthy controls(0.259×10-2 mm^(2)/s vs 0.266×10-2 mm^(2)/s,P=0.010).Lateral rectus AD of the adducted eye in concomitant strabismus patients was significantly decreased as compared with that in healthy controls(0.515×10-2 mm^(2)/s vs 0.593×10-2 mm^(2)/s,P=0.013).No statistically significant differences were present between the adducted and fixating eyes in concomitant strabismus patients.CONCLUSION:DTI represents a feasible technique to assess tissue characteristics of EOM.The effects of eye position changes on DTI parameters are subtle.Decreased MD and RD could be evidence for remodeling of the medial rectus muscle contracture.Lower medial and lateral recuts MD of concomitant esotropia patients indicates a thinner fibrous structure of the EOM.Lower MD and AD should be general character of esotropia.

Magnetic resonance diffusion tensor imaging and diffusion tensor tractography of human visual pathway

AIM: To investigate the visual pathway in normal subjects and patients with lesion involved by diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT). METHODS: Thirty normal volunteers, 3 subjects with orbital tumors involved the optic nerve (ON) and 33 subjects with occipital lobe tumors involved the optic radiation (OR) (10 gliomas, 6 meningiomas and 17 cerebral metastases) undertook routine cranium magnetic resonance imaging (MRI), DTI and DTT. Visual pathway fibers were analyzed by DTI and DTT images. Test fractional anisotropy (FA) and mean diffusivity (MD) values in different part of the visual pathway. RESULTS: The whole visual pathway but optic chiasm manifested as hyperintensity in FA maps and homogenous green signal in the direction encoded color maps. The optic chiasm did not display clearly. There was no significant difference between the bilateral FA values and MD values of normal visual pathway but optic chiasm, which the FA values tested were much too low (all P>0.05). The ONs of subjects with orbital tumors were compressed and displaced. Only one subject had lower FA values and higher MD values. OR of 9 gliomas subjects were infiltrated, with displacement in 2 and disruption in 7 subjects. All OR in 6 meniongiomas subjects were displaced. OR in 17 cerebral metastases subjects all developed displacement while 7 of them had disruption also. CONCLUSION: MR-DTI is highly sensitive in manifesting visual pathway. Visual pathway can be analyzed quantitatively in FA and MD values. DTT supplies accurate three dimensional conformations of visual pathway. But optic chiasm's manifestation still needs to improve.

Changes in a cerebellar peduncle lesion in a patient with Dandy-Walker malformation A diffusion tensor imaging study

We report a patient with severe ataxia due to Dandy-Walker malformation, who showed functional recovery over 10 months corresponding to a change in a cerebellar peduncle lesion. A 20-month-old female patient who was diagnosed with Dandy-Walker syndrome and six age- and sex-matched healthy control subjects were enrolled. The superior cerebellar peduncle, the middle cerebellar peduncle, and the inferior cerebellar peduncle were evaluated using fractional anisotropy and the apparent diffusion coefficient. The patients＇ functional ambulation category was 0 at the initial visit, but improved to 2 at the follow-up evaluation, and Berg＇s balance scale score also improved from 0 to 7. Initial diffusion tensor tractography revealed that the inferior cerebellar peduncle was not detected, that the fractional anisotropy of the superior cerebellar peduncle and middle cerebellar peduncle decreased by two standard deviations below, and that the apparent diffusion coefficient increased by two standard deviations over normal control values. However, on follow-up diffusion tensor tractography, both inferior cerebellar peduncles could be detected, and the fractional anisotropy of superior cerebellar peduncle increased to within two standard deviations of normal controls. The functional improvement in this patient appeared to correspond to changes in these cerebellar peduncles. We believe that evaluating cerebellar peduncles using diffusion tensor imaging is useful in cases when a cerebellar peduncle lesion is suspected.

Diffusion tensor tractography characteristics of axonal injury in concussion/mild traumatic brain injury

The main advantage of diffusion tensor tractography is that it allows the entire neural tract to be evaluated.In addition,configurational analysis of reconstructed neural tracts can indicate abnormalities such as tearing,narrowing,or discontinuations,which have been used to identify axonal injury of neural tracts in concussion patients.This review focuses on the characteristic features of axonal injury in concussion or mild traumatic brain injury(m TBI)patients through the use of diffusion tensor tractography.Axonal injury in concussion(m TBI)patients is characterized by their occurrence in long neural tracts and multiple injuries,and these characteristics are common in patients with diffuse axonal injury and in concussion(m TBI)patients with axonal injury.However,the discontinuation of the corticospinal tract is mostly observed in diffuse axonal injury,and partial tearing and narrowing in the subcortical white matter are frequently observed in concussion(m TBI)patients with axonal injury.This difference appears to be attributed to the observation that axonal injury in concussion(m TBI)patients is the result of weaker forces than those producing diffuse axonal injuries.In addition,regarding the fornix,in diffuse axonal injury,discontinuation of the fornical crus has been frequently reported,but in concussion(m TBI)patients,many collateral branches form in the fornix in addition to these findings in many case studies.It is presumed that the impact on the brain in TBI is relatively weaker than that in diffuse axonal injury,and that the formation of collateral branches occurs during the fornix recovery process.Although the occurrence of axonal injury in multiple areas of the brain is an important feature of diffuse axonal injury,case studies in concussion(m TBI)have shown that axonal injury occurs in multiple neural tracts.Because axonal injury lesions in m TBI patients may persist for approximately 10 years after injury onset,the characteristics of axonal injury in concussion(m TBI)patients,which are reviewed and categorized in this review,are expected to serve as useful supplementary information in the diagnosis of axonal injury in concussion(m TBI)patients.

Motor recovery via aberrant pyramidal tract in a patient with traumatic brain injury A diffusion tensor tractography study

The aberrant pyramidal tract is the collateral pathway of the pyramidal tract through the medial lemniscus in the brainstem. A 21-year-old man presented with right hemiparesis due to a traumatic intracerebral hemorrhage in the left corona radiata. His motor function recovered almost to the normal state at 10 months after onset. Through diffusion tensor tractography, the pyramidal tract in the affected （left） hemisphere showed discontinuation at the pontine level at 13 months after onset. An aberrant pyramidal tract was observed, which originated from the primary motor cortex and the supplementary motor area and descended through the corona radiata, then through the posterior limb of the internal capsule and the medial lemniscus pathway from the midbrain to the pons, finally entered into the pyramidal tract area at the pontomedullary junction, it suggests that the motor functions of the right extremities in this patient had recovered by this aberrant pyramidal tract.

Quantitative volumetric analysis of the optic radiation in the normal human brain using diffusion tensor magnetic resonance imaging-based tractography

To attain the volumetric information of the optic radiation in normal human brains, we per- formed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation fiber tract volume was a range of about 0.16% and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability fiber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are help- ful in the study of optic radiation fiber tract information.

Curvature range measurements of the arcuate fasciculus using diffusion tensor tractography

Because Broca＇s area and Wernicke＇s area in the brain are connected by the arcuate fasciculus, understanding the anatomical location and morphometry of the arcuate fasciculus can help in the treatment of patients with aphasia. We measured the horizontal and vertical curvature ranges of the arcuate fasciculus in both hemispheres in 12 healthy subjects using diffusion tensor tractography. In the right hemisphere, the direct curvature range and indirect curvature range values of the arcuate fasciculus horizontal part were 121.13 ± 5.89 and 25.99 ± 3.01 degrees, respectively, and in the left hemisphere, the values were 121.83 ± 5.33 and 27.40 ± 2.96 degrees, respectively. In the right hemisphere, the direct curvature range and indirect curvature range values of the arcuate fasciculus vertical part were 43.97 ± 7.98 and 30.15 ± 3.82 degrees, respectively, and in the left hemisphere, the values were 39.39 ± 4.42 and 24.08 ± 4.34 degrees, respectively. We believe that the measured curvature ranges are important data for localization and quantitative assessment of specific neuronal pathways in patients presenting with arcuate fasciculus abnormalities.

Compression of the bilateral corticospinal tracts by bilateral pontine hemorrhage A diffusion tensor tractography study

Bilateral spontaneous pontine hemorrhage is rare. In addition, bilateral corticospinal tract （CST） involvement in the pons may accompany serious motor sequelae. A 45-year-old right-handed woman was admitted for bilateral pontine hemorrhage. The patient presented with moderate quadriparesis at stroke onset and quickly recovered to the point of being able to extend the muscles of all four extremities against resistance, at 2 weeks from onset. At 4 weeks after stroke onset, she was able to perform all fine motor activities, as well as to walk with a normal gait. Diffusion tensor tractography results showed that the CSTs of both hemispheres originated from the primary sensorimotor cortex and descended through the corona radiata, the posterior limb of the internal capsule, midbrain, anterior pons, and the anterior medulla, along the known pathway of the CST. However, at midbrain and pons, the CSTs were compressed posterolaterally. The contralateral primary sensorimotor cortex, centered on the precentral knob, was activated during movement of either hand of the patient, as shown by functional MRI, which indicates the preservation of lateral CST. Findings from this study suggest that diffusion tensor tractography may be helpful in the elucidation of the CST status in patients with pontine hemorrhage.

Identification of the primary motor area by three-dimensional reconstruction of the corticospinal tract using diffusion tensor imaging

Functional MRI （fMRI） is widely used as a non-invasive method for the evaluation of pre-operation motor function.However,patients with cortical function impairment,such as those with hemiparesis,can rarely achieve hand clenching,a typical fMRI task for central sulcus identification,and the method is also of limited use in uncooperative children.Thus,it is important to develop a new method for identifying primary motor areas （PMA） in such individuals.This study used corticospinal tractography to identify the PMA in 20 patients with deep-seated brain tumor.Two regions of interest were set within the brainstem for corticospinal tract （CST） fiber tracking：one at the level of the pons and the other at the level of the cerebral peduncle.The CST fiber tracking results and fMRI activation signals were merged with three-dimensional anatomic MRI findings.The consistency of identifying the PMA by CST and fMRI was analyzed.fMRI activation signals were distributed mainly in the contralateral central sulcus around the omega-shaped hand knob.The CST consistently propagated from the pons and cerebral peduncle to the suspected PMA location.There was a good correlation between CST fiber tracking results and fMRI activation signals in terms of their abilities to identify the PMA.The differences between fMRI and CST fiber tracking findings may result from our functional task,which consisted only of hand movements.Our results indicate that diffusion tensor imaging is a useful brain mapping technique for identifying the PMA in paralyzed patients and uncooperative children.

Magnetic resonance diffusion tensor imaging following major ozonated autohemotherapy for treatment of acute cerebral infarction

Major ozonated autohemotherapy has been shown to promote recovery of upper limb motor function in patients with acute cerebral infarction, but whether naajor ozonated autohelnotherapy affects remote in）ury remains poorly understood. Here, we assumed that major ozonated autohemotherapy contributes to recovery of clinical function, possibly by reducing remote injury after acute cerebral infarction. Sixty acute cerebral infarction patients aged 30-80 years were equally and randomly allocated to ozone treatment and control groups. Patients in the ozone treatment group received medical treatment and major ozonated autohemotherapy （47 mg/L, 100 mL ozone） for 10 ± 2 days. Patients in the control group received medical treatment only. National Institutes of Health Stroke Scale score, modified Rankin scale score, and reduced degree of fractional anisotropy values of brain magnetic resonance diffusion tensor imaging were remarkably decreased, brain function improved, clinical efficiency significantly increased, and no obvious adverse reactions detected in the ozone treatment group compared with the control group. These findings suggest that major ozonated autohemotherapy promotes recovery of neurological function in acute cerebral infarction patients by reducing re,note injury, and additionally, exhibits high safety.

Diffusion tensor imaging detects Wallerian degeneration of the corticospinal tract early after cerebral infarction

To investigate the feasibility and time window of early detection of Wallerian degeneration in the corticospinal tract after middle cerebral artery infarction, 23 patients were assessed using magnetic resonance diffusion tensor imaging at 3.0T within 14 days after the infarction. The fractional anisotropy values of the affected corticospinal tract began to decrease at 3 days after onset and decreased in all cases at 7 days. The diffusion coefficient remained unchanged. Experimental findings indicate that diffusion tensor imaging can detect the changes associated with Wallerian degeneration of the corticospinal tract as early as 3 days after cerebral infarction.

Diffusion tensor imaging assesses white matter injury in neonates with hypoxic-ischemic encephalopathy

With improvements in care of at-risk neonates, more and more children survive. This makes it increasingly important to assess, soon after birth, the prognosis of children with hypoxic-ischemic encephalopathy. Computed tomography, ultrasound, and conventional magnetic resonance imaging are helpful to diagnose brain injury, but cannot quantify white matter damage. In this study, ten full-term infants without brain injury and twenty-two full-term neonates with hypoxic-ischemic encephalopathy （14 moderate cases and 8 severe cases） underwent diffusion tensor imaging to assess its feasibility in evaluating white matter damage in this condition. Results demonstrated that fractional anisotropy, voxel volume, and number of fiber bundles were different in some brain areas between infants with brain injury and those without brain injury. The correlation between fractional anisotropy values and neonatal behavioral neurological assessment scores was closest in the posterior limbs of the internal capsule. We conclude that diffusion tensor imaging can quantify white matter injury in neonates with hypoxic-ischemic encephalopathy.

Motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment:a diffusion tensor imaging study

Previous diffusion tensor imaging （DTI） studies regarding pediatric patients with motor dys-function have conifrmed the correlation between DTI parameters of the injured corticospinal tract and the severity of motor dysfunction. There is also evidence that DTI parameters can help predict the prognosis of motor function of patients with cerebral palsy. But few studies are re-ported on the DTI parameters that can relfect the motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment. In the present study, 36 pediatric patients with hemiplegic cerebral palsy were included. Before and after rehabilitation treatment, DTI was used to measure the ifber number （FN）, fractional anisotropy （FA） and apparent dif-fusion coefifcient （ADC） of bilateral corticospinal tracts. Functional Level of Hemiplegia scale （FxL） was used to assess the therapeutic effect of rehabilitative therapy on clinical hemiplegia. Correlation analysis was performed to assess the statistical interrelationship between the change amount of DTI parameters and FxL. DTI ifndings obtained at the initial and follow-up evalua-tions demonstrated that more affected corticospinal tract yielded signiifcantly decreased FN and FA values and signiifcantly increased ADC value compared to the less affected corticospinal tract. Correlation analysis results showed that the change amount of FxL was positively correlated to FN and FA values, and the correlation to FN was stronger than the correlation to FA. The results suggest that FN and FA values can be used to evaluate the motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment and FN is of more signiif-cance for evaluation.

Optic radiation injury in patients with aneurismal subarachnoid hemorrhage: a preliminary diffusion tensor imaging report

Visual field defect is one of the various clinical manifestations in patients with subarachnoid hemorrhage（SAH）. Little is known about the pathogenic mechanism of visual field defect in SAH. In the current study,we investigated the diffusion tensor imaging （DTI） finding of the optic radiation in patients with SAH followingrupture of a cerebral artery aneurysm. We recruited 21 patients with aneurismal SAH （12 males, 9 females, mean age, 52.67 years; range, 41–68 years） who showed no definite lesion along the visual pathway.Twenty-one age-and sex-matched normal control subjects were also recruited. DTI data were acquired at an average of 5.9 weeks （range： 3–12 weeks） after onset and reconstruction of the optic radiation was performed using DTI-Studio software. The fractional anisotropy value, apparent diffusion coefficient value,and fiber number of the optic radiation were measured. The fractional anisotropy value of the optic radiation was significantly decreased, and the apparent diffusion coefficient value was significantly increased, in patients with aneurismal SAH than in normal control subjects. However, there was no significant difference in the fiber number of the optic radiation between patients with aneurismal SAH and normal control subjects. The decrement of fractional anisotropy value and increment of apparent diffusion coefficient value of the optic radiation in patients with aneurismal SAH suggest optic radiation injury. Therefore, we recommend a thorough evaluation for optic radiation injury in patient with aneurismal SAH.

Correlation between muscular strength and basal nuclei ischemic/hemorrhagic stroke-induced corticospinal tract injury,as detected by diffusion tensor imaging and tractography

BACKGROUND： Conventional neuroimaging diagnosis does not assist with the monitoring or evaluation of basal nuclei ischemic and hemorrhagic stroke, or motor functional recovery. Magnetic resonance, diffusion tensor imaging, and diffusion tensor tractography have all been used to observe features of cerebral white matter fibrous structures. In addition, diffusion tensor tractography is the only non-invasive imaging method to display the corticospinal tract in vivo. OBJECTIVE： To evaluate the impairment degree of corticospinal tract induced by basal nuclei ischemic and hemorrhagic stroke through the use of magnetic resonance, diffusion tensor imaging, and diffusion tensor tractography, and to analyze the correlation to muscular strength. DESIGN, TIME AND SETTING： A retrospective case analysis was performed at the Department of Medical Imaging, Neurology and Neurosurgery, Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA between November 2002 and June 2008. PARTICIPANTS： A total of 15 patients with acute or subacute cerebral ischemic stroke and nine with hemorrhagic stroke in the basal nuclei were selected. METHODS： Magnetic resonance, diffusion tensor imaging, and diffusion tensor tractography results and data were analyzed. Fractional anisotropy and directionally encoded color maps were obtained. Three-dimensional tractography of bilateral corticospinal tract was created, and corticospinal tract integrity was graded. Fractional anisotropy of infarct region and corresponding contralateral normal regions were measured, and hematoma volume in hemorrhagic stroke patients was determined. Hand motor function ability was evaluated using Brunstorm criteria. MAIN OUTCOME MEASURES： Fractional anisotropy of infarct region and corresponding contralateral normal regions; hematoma volume in hemorrhagic stroke patients; correlation between muscular strength and corticospinal tract impairment degree in ischemic stroke and hemorrhagic stroke patients before and after treatment. RESULTS： In ischemic stroke patients, the fractional anisotropy value was significantly lower in the infarct area of white matter than in the normal hemisphere （P 〈 0.01）. The impairment degree of corticospinal tract negatively correlated with muscular strength of the corresponding hand （r = -0.97 P 〈 0.01）. The hematoma volume of hemorrhagic stroke patients significantly negatively correlated with Spearman test results for muscular strength of the corresponding hand （r = -0.88, P 〈 0.01）. CONCLUSION： Corticospinal tract impairment severity negatively correlated with muscular strength and motor functional recovery, which suggested that diffusion tensor imaging and diffusion tensor tractography could be used to evaluate corticospinal tract motor function.

Diffusion tensor imaging of optic nerve and optic radiation in primary chronic angle-closure glaucoma using 3T magnetic resonance imaging

AIM: To evaluate the value of quantitative diffusion tensor imaging (DTI) in assessing the axonal and myelin damage of the optic nerves and optic radiations in patients with chronic primary angle -closure glaucoma (PACG) by using high -field magnetic resonance (MR) imaging (3T). METHODS: Twenty patients with bilateral chronic PACG and twenty age - and sex matched disease -free control subjects were enrolled. Conventional MRI and DTI were performed on all subjects using 3T MR scanner. Mean diffusivity (MD), fractional anisotropy (FA), axial diffusivities (AD) and radial diffusivities (RD) of each optic nerve and each optic radiation were measured by using post -processing software of DTI studio 2.3, and then compared between left eyes and right eyes and between patients group and control group. The pairedsample t- test were used. RESULTS: There was no abnormality in the shape and signal intensity of the optic nerves and optic radiations in patients group and control group on the conventional MRI. No significant differences were observed in the FA, MD, AD and RD between the right and left optic nerves and optic radiations within patients group and control group (P>0.05). The optic nerves and optic radiations of patients with chronic PACG, as compared with control subjects, had significantly higher MD, AD, RD and significantly lower FA (P<0.05). CONCLUSION: The diffusivity of optic nerves and optic radiations in chronic PACG group showed abnormal and diffusivity parameters could be used markers of axonal and myelin injury in glaucoma.

Dynamic correlation of diffusion tensor imaging and neurological function scores in beagles with spinal cord injury

Exploring the relationship between different structure of the spinal cord and functional assessment after spinal cord injury is important. Quantitative diffusion tensor imaging can provide information about the microstructure of nerve tissue and can quantify the pathological damage of spinal cord white matter and gray matter. In this study, a custom-designed spinal cord contusion-impactor was used to damage the T_（10） spinal cord of beagles. Diffusion tensor imaging was used to observe changes in the whole spinal cord, white matter, and gray matter, and the Texas Spinal Cord Injury Score was used to assess changes in neurological function at 3 hours, 24 hours, 6 weeks, and 12 weeks after injury. With time, fractional anisotropy values after spinal cord injury showed a downward trend, and the apparent diffusion coefficient, mean diffusivity, and radial diffusivity first decreased and then increased. The apparent diffusion-coefficient value was highly associated with the Texas Spinal Cord Injury Score for the whole spinal cord（R = 0.919, P = 0.027）, white matter（R = 0.932, P = 0.021）, and gray matter（R = 0.882, P = 0.048）. Additionally, the other parameters had almost no correlation with the score（P 〉 0.05）. In conclusion, the highest and most significant correlation between diffusion parameters and neurological function was the apparent diffusion-coefficient value for white matter, indicating that it could be used to predict the recovery of neurological function accurately after spinal cord injury.

Magnetic resonance diffusion tensor imaging of optic nerve and optic radiation in healthy adults at 3T

AIM:To investigate the diffusion characteristics of water of optic nerve and optic radiation in healthy adults and its related factors by diffusion tensor imaging（DTI）at3T.METHODS:A total of 107 healthy volunteers performed head conventional MRI and bilateral optic nerve and optic radiation DTI.The primary data of DTI was processed by post-processing software of DTI studio 2.3,obtaining fractional anisotropy value,mean diffusivity value,principal engine value,orthogonal engine value by measuring,and analyzed by the SPSS13.0 statistical software.RESULTS:The bilateral optic nerve and optic radiation fibers presented green color in directional encoded color（DEC）maps and presented high signal in fractional anisotropy（FA）maps.The FA value of the left optic nerve was 0.598±0.069 and the right was 0.593±0.065;the mean diffusivity（MD）value of the left optic nerve was（1.324±0.349）×10-3mm2/s and the right was（1.312±0.350）x10-3mm2/s;the principal engine value(λ?)of the left optic nerve was（2.297±0.522）×10-4mm2/s and the right was（2.277±0.526）×10-3mm2/s;the orthogonal engine value（λ⊥）of the left optic nerve was（0.838±0.285）×10-3mm2/s and the right was（0.830±0.280）×10-3mm2/s;the FA value of the left optic radiation was 0.636±0.057 and the right was0.628±0.056;the mean diffusivity（MD）value of the left optic radiation was（0.907±0.103）×10-3mm2/s and the right was（0.889±0.125）×10-3mm2/s;the principal eigenvalue(λⅡ)of the left optic radiation was（1.655±0.210）×10-3mm2/s and the right was（1.614±0.171）×10-3mn2/s;the orthogonal enginvalue（λ⊥）of the left optic radiation was（0.531±0.103）×10-3mm2/s and the right was（0.524±0.152）×10-3mm2/s.There was no obvious difference between the FA,MD,λ‖,λ⊥of the bilateral optic radiation and the bilateral optic nerve（P】0.05）and no obvious differencebetween male and female group.The FA,MO,λ‖,λ⊥of the bilateral optic radiation and the bilateral optic nerve had no obvious correlations to the age.CONCLUSION:DTI is sensitive to the optic nerve and radiation and the relevant DTI parameters of the optic nerve and radiation are established preliminarily in this study.

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. T2 WI 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 T1 WI and T2 WI, 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.