EFFECT OF POSITIVE-INDEFINITE MATRIX ON MAGNETIC RESONANCE DIFFUSION TENSOR-DERIVED PARAMETERS

To evaluate the effect of the positive-indefinite matrix on the diffusion tensor-derived parameters, a modified algorithm is proposed for calculating these parameters. Magnetic resonance （MR） diffusion tensor images of five healthy volunteers are collected. The diffusion sensitive gradient magnetic fields are applied along 25 directions and the diffusion weighting value is 1 000 s/mm^2. Many positive-indefinite diffusion tensors can be found in the white matter area, such as the genu and the splenium of corpus callosum. Due to the positive-indefinite matrix, the mean diffusivity （MD） and the fractional anisotropy （FA） are under-estimated and over-estimated by using the conventional algorithm. Thus, the conventional algorithm is modified by using the absolute values of all eigenvalues. Results show that both the robustness and the reliability for deriving these parameters are improved by the modified algorithm.

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.

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.

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.

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.

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.

Diffusion-tensor imaging as an adjunct to dynamic contrastenhanced MRI for improved accuracy of differential diagnosis between breast ductal carcinoma in situ and invasive breast carcinoma

Objective： To determine the value of diffusion-tensor imaging （DTI） as an adjunct to dynamic contrastenhanced magnetic resonance imaging （DCE-MRI） for improved accuracy of differential diagnosis between breast ductal carcinoma in situ （DCIS） and invasive breast carcinoma （IBC）. Methods： The MRI data of 63 patients pathologically confirmed as breast cancer were analyzed. The conventional MRI analysis metrics included enhancement style, initial enhancement characteristic, maximum slope of increase, time to peak, time signal intensity curve （TIC） pattern, and signal intensity on FS- T2WI. The values of apparent diffusion coefficient （ADC）, directionally-averaged mean diffusivity （D^vg）, exponential attenuation （EA）, fractional anisotropy （FA）, volume ratio （VR） and relative anisotropy （RA） were calculated and compared between DCIS and IBC. Multivariate logistic regression was used to identify independent factors for distinguishing IBC and DCIS. The diagnostic performance of the diagnosis equation was evaluated using the receiver operating characteristic （ROC） curve. The diagnostic efficacies of DCE- MRI, DWI and DTI were compared independently or combined. Results： EA value, lesion enhancement style and TIC pattern were identified as independent factor for differential diagnosis of IBC and DCIS. The combination diagnosis showed higher diagnostic efficacy than a single use of DCE-MRI （P=0.02）, and the area of the curve was improved from 0.84 （95% CI, 0.67-0.99） to 0.94 （95% CI, 0.85-1.00）. Conclusions： Quantitative DTI measurement as an adjunct to DCE-MRI could improve the diagnostic performance of differential diagnosis between DCIS and IBC compared to a single use of DCE-MRI.

GRADING OF RABBIT SKELETAL MUSCLE TRAUMA BY DIFFUSION TENSOR IMAGING AND TRACTOGRAPHY ON MAGNETIC RESONANCE IMAGING

Objective To distinguish the edema, injury, or rupture in the traumatic skeletal muscle fiber in vivo using diffusion tensor imaging （DTI） and tractography on magnetic resonance imaging （MRI）. Methods The skeletal muscle trauma models were made in 4 rabbits （ eight hindlimbs） by iron discus （ weight 1. 0 kg, diameter 6 cm） falling down vertically from 45 cm height to rabbits＇ thighs. Conventional sequences and two-dimensional （2D） diffusion-weighted （DW） spin-echo （SE） echo planar imaging （EPI） sequence with fat suppression （ b = 600 s/mm^2 ） were performed on 1.5T MRI scanner. The grading of edema, injury, and fiber rupture in the damaged muscle were made according to their histopathological views, which was consistent with the images. The mean apparent diffusion coefficient （ADC） values and fractional anisotropy （FA） values were measured from the region of interests （ROIs） of all groups on 2D DW images used for tractography. Analysis of variance test was performed to analyze all data. Results ADC values of the areas in normal muscle, edema muscle, injury muscle, and ruptured muscle were （6. 12±1.34 ） × 10^-3, （ 6.38±1.30 ） × 10^-3, （ 8.06±0. 97 ） × 10^-3, and （ 9. 57±0. 93 ） × 10^-3 mm^2/s, respectively. There was significant difference among groups （P 〈0. 001 ）, but no difference between edema muscle and normal muscle group （P 〉0. 05）. The FA values of normal muscle, edema muscle, injury muscle, and ruptured muscle were 0. 42±0. 12, 0. 36±0. 12, 0. 26±0. 09, 0. 12±0. 08, respectively, with a significant difference among groups （ P 〈 0. 001 ）. In the edema muscle, the tracking cross-fiber could be seen but it decreased slightly. In the injury muscle, the tracking fiber decreased markedly. In the ruptured muscle, the transverse-orientation tracking fiber vanished, yet some interrupted longitudinal-orientation tracking fiber could be found. Conclsion The edema, injury, and rupture of muscle fiber in rabbit damaged skeletal muscle can be verified according to the ADC and the FA on DTI and tractography.

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.

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.

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.

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.

Diffusion tensor imaging of the brain in patients with Alzheimer's disease and cerebrovascular lesions

Background:Recent autopsy study showed a high incidence of cerebrovascular lesions in Alzheimer's disease(AD).To assess the impact of cerebrovascular pathology in AD,we used diffusion tensor imaging(DTI) to study AD patients with and without cerebrovascular lesions.Materials and Methods:Conventional and DTI scans were obtained from 10 patients with probable AD,10 AD/V patients(probable AD with cerebrovascular lesions) and ten normal controls.Mean diffusivity(D) and fractional anisotropy(FA) values of some structures involved with AD pathology were measured.Results:D value was higher in AD patients than in controls in hippocampus and the cingulate gyrus.In AD/V patients,increased D value was found in the same structures and also in the thalamus and basal ganglia compared to controls.There was a significant difference of D value between AD and AD/V patients.FA value reduced in the white matter of left inferior temporal gyrus and in the bilateral middle cingulate gyrus in patients with AD/V compared with controls.The MMSE(mini-mental state examination) score significantly correlated with FA value in the right hippocampus(r=0.639,P<0.019),in the right anterior cingulate gyrus(r=0.587,P<0.035) and in left parahippocampal gyrus(r=0.559,P<0.047).Conclusion:Cerebrovascular pathology had stronger impact on the D value than the AD pathology alone did.Elevated D value in thalamic and basal ganglia may contribute to cognitive decline in AD/V patients.Reduced FA values in AD/V patients may indicate that cerebrovascular pathology induced more severe white matter damage than the AD pathology alone did.

Prediction of motor recovery after ischemic stroke using diffusion tensor imaging： A meta-analysis

BACKGROUND: This systematic review aims to investigate the prediction value of diffusion tensor imaging for motor function recovery of ischemic stroke patients.METHODS: Cochrane Central Register of Controlled Trials(CENTRAL)(the Cochrane Library 2016, Issue 9), Pub Med, Embase, Clarivate Analytics, Scopus, CINAHL, Chinese Biomedical Literature Database, China National Knowledge Infrastructure and Google Scholar were searched for either motor recovery or corticospinal tract integrity by diffusion tensor imaging in different stroke phase from January 1, 1970, to October 31, 2016. The study design and participants were subjected to metrological analysis. Correlation coeffi cient(r) was used for evaluating the relationship between fractional anisotropy(FA) and motor function outcome. Correlation coeffi cient values were extracted from each study, and 95% confidence intervals(CIs) were calculated by Fisher's z transformation. Meta-analysis was conducted by STATA software.RESULTS: Fifteen studies with a total of 414 patients were included. Meta-analysis showed that FA in the subacute phase had the signifi cant correlation with motor function outcome(ES=0.75, 95%CI 0.62–0.87), which showed moderate quality based on GRADE system. The weight correlation coeffi cient revealed that an effect size(ES) of FA in acute phase and chronic phase was 0.51(95%CI 0.33–0.68) and 0.62(95%CI 0.47–0.77) respectively.CONCLUSION: This meta-analysis reveals that FA in the subacute phase after ischemic stroke is a good predictor for functional motor recovery, which shows moderate quality based on the GRADE system.

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.

Diffusion tensor imaging with multiple diffusion-weighted gradient directions

Diffusion tensor MRI （DT-MRI or DTI） is emerging as an important non-invasive technology for elucidating intemal brain structures. It has recently been utilized to diagnose a series of diseases that affect the integrity of neural systems to provide a basis for neuroregenerative studies. Results from the present study suggested that neural tissue is reconstructed with multiple diffusion-weighted gradient directions DTI, which varies from traditional imaging methods that utilize 6 gradient directions. Simultaneously, the diffusion tensor matrix is obtained by multiple linear regressions from an equation of echo signal intensity. The condition number value and standard deviation of fractional anisotropy for each scheme can be used to evaluate image quality. Results demonstrated that increasing gradient direction to some extent resulted in improved effects. Therefore, the traditional 6 and 15 directions should not be considered optimal scan protocols for clinical DTI application. In a scheme with 20 directions, the condition number and standard deviation of fractional anisotropy of the encoding gradients matrix were significantly reduced, and resulted in more clearly and accurately displayed neural tissue. Results demonstrated that the scheme with 20 diffusion gradient directions provided better accuracy of structural renderings and could be an optimal scan protocol for clinical DTI application.

Is combined functional magnetic resonance imaging and diffusion tensor tractography a useful tool for evaluation of somatosensory dysfunction recovery after intracerebral hemorrhage?

Diffusion tensor tractography allows the sensory fiber course of the medial lemniscus to be visualized. But diffusion tensor tractography for accurate evaluation of the repair of injured somatosensory tracts in stroke patients has been rarely reported. A 55-year-old female patient presented with severe somatosensory dysfunction of the left side caused by a spontaneous intracerebral hemorrhage on the right side. The somatosensory function of the affected side recovered to a nearly normal state at 7 weeks from onset. Functional magnetic resonance imaging revealed that at 3 weeks from onset, there was no cortical activation by touch at each hand; at 7 weeks, the contralateral cortex centered on the primary sensory cortex was found to be activated during touch and passive movements, and activation by passive movements was increased compared with that at 3 weeks. Diffusion tensor tractography revealed that a medial lemniscus on the affected （right） hemisphere was not observed at 3 weeks from onset, however, at 7 weeks, the unaffected （left） hemisphere passed along the medial lemniscus pathway from the pons to the primary sensory cortex. These findings indicate that combined functional magnetic resonance imaging and diffusion tensor tractography would allow more accurate evaluation of the architecture and integrity of somatosensory tracts and is a useful method to investigate the recovery of somatosensory dysfunction in stroke patients.

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.