Detecting dopaminergic neuronal degeneration using diffusion tensor imaging in a rotenone-induced rat model of Parkinson's disease: fractional anisotropy and mean diffusivity values

Dopamine content in the basal ganglia is strongly associated with the degree of dopaminergic neuron loss in the substantia nigra pars com- pacta. Symptoms of Parkinson＇s disease might not arise until more than 50% of the substantia nigra pars compacta is lost and the dopamine content in the basal ganglia is reduced by more than 80%. Greater diagnostic sensitivity and specificity would allow earlier detection of Parkinson＇s disease. Diffusion tensor imaging is a recently developed magnetic resonance imaging technique that measures mean diffusiv- ity and fractional anisotropy, and responds to changes in brain microstructure. When the microscopic barrier （including cell membranes, microtubules and other structures that interfere with the free diffusion of water） is destroyed and extracellular fluid volume accumulates, the mean diffusivity value increases; when the integrity of the microstructure （such as myelin） is destroyed, fractional anisotropy value decreases. However, there is no consensus as to whether these changes can reflect the early pathological alterations in Parkinson＇s disease. Here, we established a rat model of Parkinson＇s disease by injecting rotenone （or sunflower oil in controls） into the right suhstantia nigra. Diffusion tensor imaging results revealed that in the stages of disease, at 1, 2, 4, and 6 weeks after rotenone injection, fiactional anisotropy value decreased, but mean diffusivity values increased in the right substantia nigra in the experimental group. Fractional anisotropy values were lower at 4 weeks than at 6 weeks in the right substantia nigra of rats from the experimental group. Mean diffusivity values were mark- edly greater at 1 week than at 6 weeks in the right corpus striatum of rats from the experimental group. These findings suggest that mean diffusivity and fractional anisotropy values in the brain of rat models of Parkinson＇s disease 4 weeks after model establishment can reflect early degeneration of dopaminergic neurons. ＇The change in fractional anisotropy values after destruction of myelin integrity is likely to be of greater early diagnostic significance than the change in mean diffusivity values.

Diffusion tensor imaging reveals brain abnormality patterns in a patient with semantic dementia

BACKGROUND： Previous studies regarding primary progressive aphasia （PPA） have focused on progressive, non-fluent aphasia. Little information is available with regard to the use of diffusion tensor imaging compared with conventional magnetic resonance imaging for the detection of subtle structural abnormalities. OBJECTIVE： To investigate and localize brain abnormalities in a Chinese patient with semantic dementia. DESIGN, TIME AND SETTING： A concurrent, non-randomized, case-controlled, neuroimaging, clinical trial was performed at the Department of Radiology, West China Hospital of Sichuan University in March 2009. PARTICIPANTS： One 75-year-old male patient, who was diagnosed with semantic dementia, and 21 age- and gender-matched healthy volunteers were recruited for the study. METHODS： Diffusion tensor imaging was used to determine mean diffusion （MD） and fractional anisotropy （FA） in the brains of the patient and the 21 healthy subjects. Voxel-based analysis of MD and FA values was performed using statistical parametric mapping. MAIN OUTCOME MEASURES： MD and FA value maps differences between patient and controls. RESULTS： MD was significantly increased in both cerebra, but was predominant on the left side and expanded to outside of the language-related region. Reduced MD was not detected in any of the brains. FA was shown to be decreased in the corpus callosum, but was increased in the basal ganglia. CONCLUSION： The present study provided clear in vivo magnetic imaging evidence of diffuse brain involvement in semantic dementia. Increases in MD were greater than in FA when brain diffusion alterations were detected, which suggested that MD could be a better marker of disease progression.

Classification of Intervertebral Disc Degeneration in Low Back Pain Using Diffusional Kurtosis Imaging

Degenerative disc disease is the most common cause of low back pain. Intervertebral disc abnormalities are commonly evaluated by magnetic resonance imaging (MRI), and Pfirrmann’s system involves the use of T2-weighted images (T2WI) to classify disc degeneration. However, as this classification is based on visual evaluation, it is not possible to quantify degeneration using this method. The present study was performed to establish an MRI-based intervertebral disc classification system using diffusional kurtosis imaging (DKI), to quantify intervertebral disc water content according to the Pfirrmann classification. Sagittal mean diffusional kurtosis (MK) mapping was performed for the L3/4, L4/5, and L5/S1 intervertebral discs in 32 patients (15 female, 17 male;age range, 24 - 82 years;mean age, 57.7 years). The degree of disc degeneration was assessed in the midsagittal section on T2WI according to the Pfirrmann classification (grade I - V). The relationships between MK values, which are correlated with intervertebral disc composition changes, and grade of degeneration determined using the Pfirrmann classification were analyzed. The MK values tended to decrease with increasing grade of degeneration, and differed significantly between grades I and IV, but not between grade IV and V (P < 0.05, Mann-Whitney U test). DKI is an effective means of detecting the early stages of disc degeneration. Therefore, DKI may be a useful diagnostic tool for quantitative assessment of intervertebral disc degeneration.

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.

Correlations between hippocampal functional connectivity,structural changes,and clinical data in patients with relapsing-remitting multiple sclerosis:a case-control study using multimodal magnetic resonance imaging

Multiple sclerosis is associated with structural and functional brain alterations leading to cognitive impairments across multiple domains including attention,memory,and the speed of information processing.The hippocampus,which is a brain important structure involved in memory,undergoes microstructural changes in the early stage of multiple sclerosis.In this study,we analyzed hippocampal function and structure in patients with relapsing-remitting multiple sclerosis and explored correlations between the functional connectivity of the hippocampus to the whole brain,changes in local brain function and microstructure,and cognitive function at rest.We retrospectively analyzed data from 20 relapsing-remitting multiple sclerosis patients admitted to the Department of Neurology at the China-Japan Union Hospital of Jilin University,China,from April 2015 to November 2019.Sixteen healthy volunteers were recruited as the healthy control group.All participants were evaluated using a scale of extended disability status and the Montreal cognitive assessment within 1 week before and after head diffusion tensor imaging and functional magnetic resonance imaging.Compared with the healthy control group,the patients with relapsing-remitting multiple sclerosis had lower Montreal cognitive assessment scores and regions of simultaneously enhanced and attenuated whole-brain functional connectivity and local functional connectivity in the bilateral hippocampus.Hippocampal diffusion tensor imaging data showed that,compared with the healthy control group,patients with relapsing-remitting multiple sclerosis had lower hippocampal fractional anisotropy values and higher mean diffusivity values,suggesting abnormal hippocampal structure.The left hippocampus whole-brain functional connectivity was negatively correlated with the Montreal cognitive assessment score(r=-0.698,P=0.025),and whole-brain functional connectivity of the right hippocampus was negatively correlated with extended disability status scale score(r=-0.649,P=0.042).The mean diffusivity value of the left hippocampus was negatively correlated with the Montreal cognitive assessment score(r=-0.729,P=0.017)and positively correlated with the extended disability status scale score(r=0.653,P=0.041).The right hippocampal mean diffusivity value was positively correlated with the extended disability status scale score(r=0.684,P=0.029).These data suggest that the functional connectivity and presence of structural abnormalities in the hippocampus in patients with relapse-remission multiple sclerosis are correlated with the degree of cognitive function and extent of disability.This study was approved by the Ethics Committee of China-Japan Union Hospital of Jilin University,China(approval No.201702202)on February 22,2017.