A VARIATIONAL PROBLEM ARISING IN REGISTRATION OF DIFFUSION TENSOR IMAGES

The existence of a global minimizer for a variational problem arising in registration of diffusion tensor images is proved, which ensures that there is a regular spatial transformation for the registration of diffusion tensor images.

A robust tensor watermarking algorithm for diffusion-tensor images

Watermarking algorithms that use convolution neural networks have exhibited good robustness in studies of deep learning networks.However,after embedding watermark signals by convolution,the feature fusion eficiency of convolution is relatively low;this can easily lead to distortion in the embedded image.When distortion occurs in medical images,especially in diffusion tensor images(DTIs),the clinical value of the DTI is lost.To address this issue,a robust watermarking algorithm for DTIs implemented by fusing convolution with a Transformer is proposed to ensure the robustness of the watermark and the consistency of sampling distance,which enhances the quality of the reconstructed image of the watermarked DTIs after embedding the watermark signals.In the watermark-embedding network,Ti-weighted(Tlw)images are used as prior knowledge.The correlation between T1w images and the original DTI is proposed to calculate the most significant features from the T1w images by using the Transformer mechanism.The maximum of the correlation is used as the most significant feature weight to improve the quality of the reconstructed DTI.In the watermark extraction network,the most significant watermark features from the watermarked DTI are adequately learned by the Transformer to robustly extract the watermark signals from the watermark features.Experimental results show that the average peak signal-to-noise ratio of the watermarked DTI reaches 50.47 dB,the diffusion characteristics such as mean diffusivity and fractional anisotropy remain unchanged,and the main axis deflection angleαAc is close to 1.Our proposed algorithm can effectively protect the copyright of the DTI and barely affects the clinical diagnosis.

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.

Appearance of a neural bypass between injured cingulum and brainstem cholinergic nuclei of a patient with traumatic brain injury on follow-up diffusion tensor tractography images

The human brain is known to contain a maximum of eight cholinergic nuclei： the basal forebrain region： the medial septal nucleus （Ch 1）, the vertical nucleus of the diagonal band （Ch 2）, the horizontal limb of the diago- nal band （Ch 3）, and the nucleus basalis of Meynert （Ch 4）; the brainstem： the pedunculopontine nucleus （Ch 5）, the laterodorsal tegmental nucleus （Ch 6）, and the para- bigeminal nucleus （Ch 8）; and the thalamus： the medial habenular nucleus （Ch 7） （Nieuwenhuys et al., 2008; Naidich and Duvernoy, 2009）. The cingulum is the neu- ral tract extending from the orbitofrontal cortex to the medial temporal lobe （Mufson and Pandya, 1984）. The cingulum plays an important role in memory because it is a passage of the medial cholinergic pathway, which pro- vides cholinergic innervations to the cerebral cortex after originating from Ch 1 and Ch 2 as well as Ch 4 （mainly） （Selden et al., 1998; Nieuwenhuys et al., 2008; Hong and lang, 2010）.

Glymphatic function and its influencing factors in different glucose metabolism states

BACKGROUND Dysfunction of the glymphatic system in the brain in different stages of altered glucose metabolism and its influencing factors are not well characterized.AIM To investigate the function of the glymphatic system and its clinical correlates in patients with different glucose metabolism states,the present study employed diffusion tensor imaging along the perivascular space(DTI-ALPS)index.METHODS Sample size was calculated using the pwr package in R software.This crosssectional study enrolled 22 patients with normal glucose metabolism(NGM),20 patients with prediabetes,and 22 patients with type 2 diabetes mellitus(T2DM).A 3.0T magnetic resonance imaging was used to evaluate the function of the glymphatic system.The mini-mental state examination(MMSE)was used to assess general cognitive function.The DTI-ALPS index of bilateral basal ganglia and the mean DTI-ALPS index was calculated.Further,the correlation between DTI-ALPS and clinical features was assessed.RESULTS The left-side,right-side,and mean DTI-ALPS index in the T2DM group were significantly lower than that in the NGM group.The right-side DTI-ALPS and mean DTI-ALPS index in the T2DM group were significantly lower than those in the prediabetes group.DTI-ALPS index lateralization was not observed.The MMSE score in the T2DM group was significantly lower than that in the NGM and prediabetes group.After controlling for sex,the left-side DTI-ALPS and mean DTI-ALPS index in the prediabetes group were positively correlated with 2-hour postprandial blood glucose level;the left-side DTI-ALPS index was negatively correlated with total cholesterol and low-density lipoprotein level.The right-side DTI-ALPS and mean DTI-ALPS index were negatively correlated with the glycosylated hemoglobin level and waist-to-hip ratio in the prediabetes group.The left-side,right-side,and mean DTI-ALPS index in the T2DM group were positively correlated with height.The left-side and mean DTIALPS index in the T2DM group were negatively correlated with high-density lipoprotein levels.CONCLUSION Cerebral glymphatic system dysfunction may mainly occur in the T2DM stage.Various clinical variables were found to affect the DTI-ALPS index in different glucose metabolism states.This study enhances our understanding of the pathophysiology of diabetic brain damage and provides some potential biological evidence for its early diagnosis.

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.

Glymphatic system function in diverse glucose metabolism states

The rising prevalence of diabetes and prediabetes globally necessitates a deeper understanding of associated complications,including glymphatic system dysfunction.The glymphatic system,crucial for brain waste clearance,is implicated in cognitive decline and neurodegenerative diseases like Alzheimer’s disease.This letter explores recent research on glymphatic function across different glucose metabolism states.Tian et al’s study reveals significant glymphatic dysfunction in type 2 diabetes mellitus patients,evidenced by lower diffusion tensor imaging analysis along perivascular space indices compared to those with normal glucose metabolism and prediabetes.The research also reveals a link between glymphatic dysfunction and cognitive impairment.Additional research underscores the role of glymphatic impairment in neurodegenerative diseases.These findings highlight the importance of integrating glymphatic health into diabetes management and suggest potential biomarkers for early diagnosis and targeted therapeutic interventions.

Multimodal abnormalities of brain structures in adolescents and young adults with major depressive disorder:An activation likelihood estimation meta-analysis

BACKGROUND Major depressive disorder(MDD)in adolescents and young adults contributes significantly to global morbidity,with inconsistent findings on brain structural changes from structural magnetic resonance imaging studies.Activation likeli-hood estimation(ALE)offers a method to synthesize these diverse findings and identify consistent brain anomalies.METHODS We performed a comprehensive literature search in PubMed,Web of Science,Embase,and Chinese National Knowledge Infrastructure databases for neuroi-maging studies on MDD among adolescents and young adults published up to November 19,2023.Two independent researchers performed the study selection,quality assessment,and data extraction.The ALE technique was employed to synthesize findings on localized brain function anomalies in MDD patients,which was supplemented by sensitivity analyses.RESULTS Twenty-two studies comprising fourteen diffusion tensor imaging(DTI)studies and eight voxel-based morphome-try(VBM)studies,and involving 451 MDD patients and 465 healthy controls(HCs)for DTI and 664 MDD patients and 946 HCs for VBM,were included.DTI-based ALE demonstrated significant reductions in fractional anisotropy(FA)values in the right caudate head,right insula,and right lentiform nucleus putamen in adolescents and young adults with MDD compared to HCs,with no regions exhibiting increased FA values.VBM-based ALE did not demonstrate significant alterations in gray matter volume.Sensitivity analyses highlighted consistent findings in the right caudate head(11 of 14 analyses),right insula(10 of 14 analyses),and right lentiform nucleus putamen(11 of 14 analyses).CONCLUSION Structural alterations in the right caudate head,right insula,and right lentiform nucleus putamen in young MDD patients may contribute to its recurrent nature,offering insights for targeted therapies.

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.

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.

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.

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.

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.

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.

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.

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.