Diffusion tensor tractography can predict hemiparesis in infants with high risk factors

Diffusion tensor tractography (DTT) is known to be useful in detecting white matter lesions. In the current study, we report on two hemiparetic patients with risk factors who showed abnormalities of the corticospinal tract (CST) on diffusion tensor tractography (DTT) prior to the manifestation of hemiparesis. Two hemiparetic patients with risk factors (preterm, low birth weight) and six age-matched normal control subjects were enrolled to this study. Diffusion tensor imaging (DTI) was performed at the age of 43 weeks (patient 1) and 33 weeks (patient 2) using 1.5-T with a Synergy-L Sensitivity Encoding (SENSE) head coil. We measured fractional anisotropy (FA), apparent diffusion coefficients (ADCs), and fiber counts of the CST. There were no definite asymmetric findings on physical examination and conventional brain MRI. By contrast, DTT showed a unilateral CST disruption at the periventricular white matter, low FA values, and low CST fiber counts compared with those of the unaffected CST and controls. These patients were diagnosed with hemiparetic cerebral palsy when we re-evaluated these patients at the age of 6 years (patient 1) and 3 years of age (patient 2), respectively. In these two patients, DTT revealed abnormalities of the CST prior to the manifestation of hemiparesis. Therefore, it seems that DTT would be a useful modality in detecting CST abnormalities in advance of clinical manifestation in infants with high risk factors.     

Usefulness of diffusion tensor imaging in patients who showed sustained unexplainable clinical symptom of torticollis

To investigate corticospinal tract (CST) status using diffusion tensor imaging (DTI) in patients who had clinical symptom of torticollis but no definite cause of sustained symptom of torticollis. We evaluated 10 patients with sustained torticollis and 12 age-matched control subjects. All patients showed no specific fibromatosis coli findings on neck sonography. Even after intensive manual therapy, there was no improvement of clinical symptom of torticollis. DTI was performed using 1.5 T with a synergy-L Sensitivity Encoding (SENSE) head coil. Fractional anisotropy and apparent diffusion coefficient were measured using the region of interest method, and diffusion tensor tractography was conducted. We estimated the asymmetric anisotropic index (AA) and asymmetric mean diffusivity index (AD) to evaluate the asymmetry between right and left CSTs. All patients showed only torticollis symptom but no definite hemiplegic pattern on their extremities at initial evaluation. DTT, which was performed to reveal the reason of sustained asymmetric postural symptom showed hemiplegic pattern. The results of DTT corresponded to the delayed hemiplegic symptoms, which were found in the patients at second evaluation. AA and AD values between patients and control group were significantly different. Torticollis is usually caused by fibromatosis coli, but may be one of the symptoms of hemiplegia. DTI may be an additional technique for the early detection of hemiplegia in patients with sustained symptoms of unexplainable postural torticollis.     

White matter changes in mild cognitive impairment and AD: A diffusion tensor imaging study

Diffusion tensor imaging (DTI) can detect, in vivo, the directionality of molecular diffusion and estimate the microstructural integrity of white matter (WM) tracts. In this study, we examined WM changes in patients with Alzheimer's disease (AD) and in subjects with amnestic mild cognitive impairment (MCI) who are at greater risk for developing AD. A DTI index of WM integrity, fractional anisotropy (FA), was calculated in 14 patients with probable mild AD, 14 participants with MCI and 21 elderly healthy controls (NC). Voxel-by-voxel comparisons showed significant regional reductions of FA in participants with MCI and AD compared to controls in multiple posterior white matter regions. Moreover, there was substantial overlap of locations of regional decrease in FA in the MCI and AD groups. These data demonstrate that white matter changes occur in MCI, prior to the development of dementia.     

Supervised learning of postural tasks in patients with poststroke hemiparesis, Parkinson’s disease or cerebellar ataxia

Supervised learning of different postural tasks in patients with lesions of the motor cortex or pyramidal system (poststroke hemiparesis: 20 patients), nigro-striatal system (Parkinson’s disease: 33 patients) and cerebellum (spinocerebellar ataxia: 37 patients) was studied. A control group consisted of 13 healthy subjects. The subjects stood on a force platform and were trained to change the position of the center of pressure (CP) presented as a cursor on a monitor screen in front of the patient. Subjects were instructed to align the CP with the target and then move the target by shifting the CP in the indicated direction. Two different tasks were used. In “Balls”, the target (a ball) position varied randomly, so the subject learned a general strategy of voluntary CP control. In “Bricks”, the subject had to always move the target in a single direction (downward) from the top to the bottom of the screen, so that a precise postural coordination had to be learned. The training consisted of 10 sessions for each task. The number of correctly performed trials for a session (2 min for each task) was scored. The voluntary control of the CP position was initially impaired in all groups of patients in both tasks. In “Balls”, there were no differences between the groups of the patients on the first day. The learning course was somewhat better in hemiparetic patients than in the other groups. In “Bricks”, the initial deficit was greater in the groups of parkinsonian and cerebellar patients than in hemiparetic patients. However, learning was more efficient in parkinsonian than in hemiparetic and cerebellar patients. After 10 days of training, the hemiparetic and cerebellar patients completed the acquisition at a certain level whereas the parkinsonian patients showed the ability for further improvement. The results suggest that motor cortex, cerebellum, and basal ganglia are involved in voluntary control of posture and learning different postural tasks. However, these structures play different roles in postural control and learning: basal ganglia are mainly involved in learning a general strategy of CP control while the function of the motor cortex chiefly concerns learning a specific CP trajectory. The cerebellum is involved in both kinds of learning.     

The role of diffusion tensor imaging in the evaluation of ischemic brain injury - a review

Water diffusion in brain tissue is affected by the presence of barriers to translational motion such as cell membranes and myelin fibers. The measured water apparent diffusion coefficient (ADC) value is therefore frequently anisotropic and varies depending upon the orientation of restricting barriers (such as white matter tracts) relative to the diffusion-sensitive-gradient direction. Anisotropic water diffusion can be specified using indices of diffusion anisotropy [e.g. standard deviation of the individual ADC values, fractional anisotropy (FA), lattice index (LI)], which are derived from measurements of the full diffusion tensor. The rotationally invariant nature of particular diffusion anisotropy indices (e.g. FA, LI) allows orientation-independent comparisons of these parameters between different subjects. Pathophysiological processes (such as cerebral ischemia) that modify the integrity of the tissue microstructure result in significant alterations in tissue anisotropy and make this metric a useful endpoint for characterizing the temporal evolution of the disease. Diffusion-tensor imaging (DTI) studies of both experimental and human stroke suggest that DTI may provide additional information about the evolution of the disease that is not available from diffusion-weighted MRI (DWI) alone. Acute reductions in the average diffusivity [ = (lambda(1) + lambda(2) + lambda(3))/3 where lambda(1), lambda(2), and lambda(3) are the eigenvalues of the diffusion tensor] following the onset of cerebral ischemia are often accompanied by increases in diffusion anisotropy. In the transition from acute to sub-acute and chronic stroke, renormalizes and subsequently increases whereas diffusion anisotropy measures (e.g. FA) decline and remained reduced in chronic infarcts. Overall isotropic ADC changes during infarct evolution have been observed to be greater in white matter (WM) than in gray matter (GM) lesions (although there have been conflicting reports on this issue) and GM lesions tend to renormalize prior to WM lesions as the infarct evolves. Ischemic WM exhibits a significant decrease in diffusion anisotropy (relative to normal WM) during ischemic evolution whereas that of ischemic GM remains statistically unchanged. Furthermore, the percentage decrease in ischemic WM is largely determined by reductions in lambda(1), the eigenvalue that coincides with the long axis of the WM fiber tract. Variations in unidirectional ADC or over the ischemic time course limit the usefulness of this parameter alone as a predictor of ischemic injury. Consequently, ADC information has been combined with that of other MR parameters (including DTI) to unambiguously stage and predict ischemic brain injury over its entire temporal evolution. Combined and diffusion anisotropy measurements have identified three phases of diffusion abnormality: (1) reduced and elevated anisotropy; (2) reduced and reduced anisotropy; and (3) elevated and reduced anisotropy. However, variations in the differential patterns of and diffusion anisotropy evolution have been observed by a number of investigators and more work is needed to clarify the role of these measurements in characterizing the severity of the ischemic insult as well as the potential outcome in response to the initial ischemic injury. The use of DTI, in combination with more sophisticated analysis methods for performing multiparametric segmentation, such as multispectral analysis, may enhance the use of MRI for accurate diagnosis and prognosis of stroke. Furthermore, these techniques may also play an important role in the clinical evaluation of new stroke treatments.     

In vivo diffusion MRI detects early spinal cord axonal pathology in a mouse model of amyotrophic lateral sclerosis

Diffusion magnetic resonance imaging (MRI) exhibits contrast that identifies macro‐ and microstructural changes in neurodegenerative diseases. Previous studies have shown that MR diffusion tensor imaging (DTI) can observe changes in spinal cord white matter in animals and humans affected with symptomatic amyotrophic lateral sclerosis (ALS). The goal of this preclinical work was to investigate the sensitivity of DTI for the detection of signs of tissue damage before symptoms appear. High‐field MRI data were acquired using a 9.4‐T animal scanner to examine the spinal cord of an ALS mouse model at pre‐ and post‐symptomatic stages (days 80 and 120, respectively). The MRI results were validated using yellow fluorescent protein (YFP) via optical microscopy of spinal cord tissue slices collected from the YFP,G93A‐SOD1 mouse strain. DTI maps of diffusion‐weighted imaging (DWI) signal intensity, mean diffusivity (MD), fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD) were computed for axial slices of the lumbar region of the spinal cord. Significant changes were observed in FA (6.7% decrease, p < 0.01), AD (19.5% decrease, p < 0.01) and RD (16.1% increase, p < 0.001) at postnatal day 80 (P80). These differences were correlated with changes in axonal fluorescence intensity and membrane cellular markers. This study demonstrates the value of DTI as a potential tool to detect the underlying pathological progression associated with ALS, and may accelerate the discovery of therapeutic strategies for patients with this disease.     

Neuropsychological correlates of diffusion tensor imaging in schizophrenia

Patients with schizophrenia (n = 41) and healthy comparison participants (n = 46) completed neuropsychological measures of intelligence, memory, and executive function. A subset of each group also completed magnetic resonance diffusion tensor imaging (DTI) studies (fractional anisotropy and cross-sectional area) of the uncinate fasciculus (UF) and cingulate bundle (CB). Patients with schizophrenia showed reduced levels of functioning across all neuropsychological measures. In addition, selective neuropsychological-DTI relationships emerged. Among patients but not controls, lower levels of declarative-episodic verbal memory correlated with reduced left UF, whereas executive function errors related to performance monitoring correlated with reduced left CB. The data suggested abnormal DTI patterns linking declarative-episodic verbal memory deficits to the left UF and executive function deficits to the left CB among patients with schizophrenia.     

Quantification of cerebral edema on diffusion tensor imaging in acute-on-chronic liver failure

Cerebral edema is a major complication of acute liver failure but may also be seen in other forms of liver failure such as acute-on-chronic liver failure (ACLF) and chronic liver failure (CLF). ACLF develops in patients with previously well-compensated chronic liver disease following acute hepatitis A or E superimposed on underlying liver cirrhosis. The aim of this study was to detect the occurrence, and determine the nature, of cerebral edema in patients with the defined subset of ACLF using diffusion tensor imaging (DTI) metrics. Twenty-three patients with ACLF were studied and compared with 15 healthy controls and 15 patients with CLF. DTI metrics including fractional anisotropy (FA), mean diffusivity (MD), linear anisotropy (CL), planar anisotropy (CP), and spherical isotropy (CS) were calculated by selecting regions of interest in the white matter and deep grey matter of the brain. Significantly decreased FA and increased CS were observed in the anterior limb (ALIC) and posterior limb (PLIC) of the internal capsule and frontal white matter (P<0.05) in patients with different grades (1-4) of ACLF when compared with healthy controls. No significant changes in MD and CP were seen in any brain region. However, significantly decreased CL was observed in the PLIC, caudate nuclei and putamen. In patients with CLF, significantly decreased FA with increased CS in the ALIC and PLIC along with significantly increased MD in the ALIC and caudate nuclei were observed. The presence of significantly decreased FA and CL and increased CS along with no significant change in MD and CP suggests the presence of both intracellular and extracellular components of cerebral edema in patients with ACLF.     

Diffusion tensor imaging and Tract-Based Spatial Statistics in Alzheimer's disease and mild cognitive impairment

We aimed to explore the changes in fractional anisotropy (FA) in subjects with mild cognitive impairment (MCI) and Alzheimer's disease (AD) by analyzing diffusion tensor imaging (DTI) data using the Tract-Based Spatial Statistics (TBSS). DTI data were collected from 17 AD patients, 27 MCI subjects and 19 healthy controls. Voxel-based analysis with TBSS was used to compare FA among the three groups. Additionally, guided by TBSS findings, a region of interest (ROI)-based analysis along the TBSS skeleton was performed on group-level and the accuracy of the method was assessed by the back-projection of ROIs to the native space FA. Neurofiber tracts with decreased FA included: the parahippocampal white matter, cingulum, uncinate fasciculus, inferior and superior longitudinal fasciculus, corpus callosum, fornix, tracts in brain stem, and cerebellar tracts. Quantitative ROI-analysis further demonstrated the significant decrease on FA values in AD patients relative to controls whereas FA values of MCI patients were found in between the controls and AD patients. We conclude that TBSS is a promising method in examining the degeneration of neurofiber tracts in MCI and AD patients.     

A meta-analysis of diffusion tensor imaging in mild cognitive impairment and Alzheimer's disease

We reviewed case-control studies of diffusion tensor imaging (DTI) in patients with Alzheimer's dementia (AD) and mild cognitive impairment (MCI), in order to establish the relative severity and location of white matter microstructural changes. EMBASE and MEDLINE were searched using the keywords, ([“diffusion tensor”] and [“Alzheimer*” or “mild cognitive impairment”]), as were reference lists of relevant papers. Forty-one diffusion tensor imaging studies contained data that were suitable for inclusion. Group means and standard deviations for fractional anisotropy and mean diffusivity, or p values from 2-sample tests, were extracted and pooled, using standard methods of meta-analysis and metaregression. Fractional anisotropy was decreased in AD in all regions except parietal white matter and internal capsule, while patients with MCI had lower values in all white matter regions except parietally and occipitally. Mean diffusivity was increased in AD in all regions, and in MCI in all but occipital and frontal regions.     

Assessment of the systematic errors caused by diffusion gradient inhomogeneity in DTI‐computer simulations

Diffusion tensor imaging (DTI) is a powerful MRI modality that allows the investigation of the microstructure of tissues both in vivo and noninvasively. Its reliability is strictly dependent on the performance of diffusion‐sensitizing gradients, of which spatial nonuniformity is a known issue in the case of virtually all clinical MRI scanners. The influence of diffusion gradient inhomogeneity on the accuracy of the diffusion tensor imaging was investigated by means of computer simulations supported by an MRI experiment performed at the isocenter and 15 cm away. The DTI measurements of two diffusion phantoms were simulated assuming a nonuniform diffusion‐sensitizing gradient and various levels of noise. Thereafter, the tensors were calculated by two methods: (i) assuming a spatially constant b‐matrix (standard DTI) and (ii) applying the b‐matrix spatial distribution in the DTI (BSD‐DTI) technique, a method of indicating the b‐matrix for each voxel separately using an anisotropic phantom as a standard of diffusion. The average eigenvalues and fractional anisotropy across the homogeneous region of interest were calculated and compared with the expected values. Diffusion gradient inhomogeneity leads to overestimation of the largest eigenvalue, underestimation of the smallest one and thus overestimation of fractional anisotropy. The effect is similar to that caused by noise; however, it could not be corrected by increasing SNR. The MRI measurements, performed using a 3 T clinical scanner, revealed that the split of the eigenvalues measured 15 cm away from the isocenter is significant (up to 25%). The BSD‐DTI calibration allowed the reduction of the measured fractional anisotropy of the isotropic medium from 0.174 to 0.031, suggesting that gradient inhomogeneity was the main cause of this error. For the phantom measured at the isocenter, however, the split was almost not observed; the average eigenvalues were shifted from the expected value by ~ 5%.     

Diffusion tensor MRI in rat models of invasive and well-demarcated brain tumors

Diffusion tensor imaging (DTI) and its metrics, such as mean diffusivity (MD) and fractional anisotropy (FA), have been used to detect the extent of brain tumors and understand tumor growth and its influence on the surrounding tissue. However, there are conflicting reports on how DTI metrics can be used for tumor diagnosis. The physiological interpretation of these metrics in terms of tumor growth is also not clear. The objective of this study was to investigate the DTI parameters in two rat brain tumor models (9L and F98) with different patterns of aggressiveness by longitudinal monitoring of tumor growth and comparing the DTI parameters of these two tumor models. In addition to the standard DTI metrics, MD and FA, we measured other metrics representing diffusion tensor shape, such as linear and planar anisotropy coefficients (CL and CP), and orientational coherence measured by lattice index (LI), to characterize the two tumor models. The 9L tumor had higher FA, CL, and LI than the F98 tumor. F98 had a larger difference in anisotropies between tumor and peritumor regions than 9L. From the eigenvalues, it was found that the increase in CL and trace of the 9L tumor was due to an increase in the primary eigenvalue, whereas the increase in CP in the peritumor region was due to an increase in both primary and secondary eigenvalues and a decrease in tertiary eigenvalue. Our results indicate that shape-oriented anisotropy measures, such as CL and CP, and orientational coherence measures, such as LI, can provide useful information in differentiating these two tumor models and also differentiating tumor from peritumoral regions.     

磁共振扩散张量成像序列对脊髓型颈椎病的诊断价值

目的:分析3.0T磁共振（MR）扩散张量成像（DTI）序列对脊髓型颈椎病（CSM）的诊断价值。方法:选择福建中医药大学附属康复医院收治的30例CSM患者纳入观察组,另选择同期体检人群中年龄匹配的30例健康志愿者为对照组,均运用常规MRI序列及DTI技术进行扫描,运用DTI技术测量FA及ADC值,进行图像后处理及数据分析,观察组患者根据MR平扫结果分为A组（n=10,单纯硬膜囊受压）、B组（n=14,颈髓受压,信号正常）和C组（n=6,颈髓受压,T2WI高信号）,分析各组FA及DA值差异,评价DTI诊断脊髓型颈椎病的诊断价值。结果:对照组脊髓C2-3、C3-4、C4-5、C5-6、C6-7节段的ADC值与FA比较差异无统计学意义（P>0.05）;对照组与A、B、C组的ADC值、FA值存在显著性差异（P<0.05）,B组、C组的ADC值显著高于对照组（P<0.05）,FA值显著低于对照组（P<0.05）,A组ADC值、FA值与对照组比较差异无统计学意义（P>0.05）;从A组到C组,ADC值呈升高趋势,FA值呈降低趋势,差异显著（P<0.05）;MR T2WI、DTI序列扫描FA值、MR DTI序列扫描ADC值诊断扫描诊断CSM的敏感度与特异度为20.00%（6/30）与80.00%（24/30）,80.00%（24/30）与20.00%（6/30）,66.67%（20/30）与30.00%（9/30）。结论:DTI较常规MRI能更早期而准确地诊断CSM,是一种显示CSM病变和观察病变修复过程的有效手段。     

Diffusion tensor imaging of two unrelated Chinese men with hereditary spastic paraplegia associated with thin corpus callosum

Hereditary spastic paraplegia (HSP) associated with thin corpus callosum is a rare autosomal recessive neurodegenerative disorder characterized by an abnormally thin corpus callosum, normal motor development, slowly progressive spastic paraparesis and cognitive deterioration. To investigate and localize abnormalities in the brains of two Chinese patients with HSP-TCC, with mutations in the spatacsin gene. Diffusion tensor imaging (DTI) was used to determine the mean diffusion (MD) and fractional anisotropy (FA) in the brains of the patients in comparison to 20 healthy subjects. Voxel-based analysis (VBA) of both the diffusion and anisotropy values were performed using statistical parametric mapping (SPM). Significant changes with MD increase and FA reduction were found in the already known lesions including the corpus callosum, cerebellum and thalamus. In addition, changes were also found in regions that appear to be normal in conventional MRI, such as the brain stem, internal capsule, cingulum and subcortical white matter including superior longitudinal fascicle and inferior longitudinal fascicle. Neither increase in FA nor reduction in MD was detected in the brain. Our study provides clear in vivo MR imaging evidence of a more widespread brain involvement of HSP-TCC. MD is more sensitive than FA in detecting lesions in thalamus and subcortical white matter, suggesting that MD may be a better marker of the disease progression.     

Comparison of Regional Gray Matter Atrophy,White Matter Alteration,and Glucose Metabolism as a Predictor of the Conversion to Alzheimer's Disease in Mild Cognitive Impairment

We compared the predictive ability of the various neuroimaging tools and determined the most cost-effective, non-invasive Alzheimer''s disease (AD) prediction model in mild cognitive impairment (MCI) individuals. Thirty-two MCI subjects were evaluated at baseline with [¹⁸F]-fluorodeoxyglucose positron emission tomography (FDG-PET), MRI, diffusion tensor imaging (DTI), and neuropsychological tests, and then followed up for 2 yr. After a follow up period, 12 MCI subjects converted to AD (MCIc) and 20 did not (MCInc). Of the voxel-based statistical comparisons of baseline neuroimaging data, the MCIc showed reduced cerebral glucose metabolism (CMgl) in the temporo-parietal, posterior cingulate, precuneus, and frontal regions, and gray matter (GM) density in multiple cortical areas including the frontal, temporal and parietal regions compared to the MCInc, whereas regional fractional anisotropy derived from DTI were not significantly different between the two groups. The MCIc also had lower Mini-Mental State Examination (MMSE) score than the MCInc. Through a series of model selection steps, the MMSE combined with CMgl model was selected as a final model (classification accuracy 93.8%). In conclusion, the combination of MMSE with regional CMgl measurement based on FDG-PET is probably the most efficient, non-invasive method to predict AD in MCI individuals after a two-year follow-up period.

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White matter impairment in heroin addicts undergoing methadone maintenance treatment and prolonged abstinence: a preliminary DTI study

Methadone maintenance treatment (MMT) might cause the impairments of neuropsychological and neurotransmitter function in opioid addicts. Whether long-term MMT could lead to the impairment of white matter (WM) in heroin addiction brain is unclear. This study compared the WM integrity in the bilateral frontal lobe, temporal lobe, splenium and genu of corpus collasum (CC) between MMT patients (n=13), former heroin addicts (n=11) in prolonged abstinence (PA), and healthy control subjects (n=15) using diffusion tensor imaging (DTI). Fractional anisotropy (FA), apparent diffusion coefficient (ADC) and eigenvalues (λ(⊥), λ(||)) were measured. The correlation between DTI measures and accumulated former heroin dose, total methadone consumption, and PA duration were determined. Although the PA subjects showed no difference in DTI measures relative to the controls, the extensive correlations between the former heroin consumption and the DTI measures were noted. The MMT subjects showed a decreased FA values in the left genu, as well as the increased ADC and λ(⊥) values in the left splenium of CC in comparison to the controls. Compared with the PA, the MMT subjects had a significantly increased ADC value in the bilateral splenium of CC. Importantly, the methadone dosage used in the MMT group was correlated with the FA value in the left splenium of CC and in the right frontal lobe. Our preliminary results suggest that methadone plays a role in the impairment of WM integrity in heroin users on long-term MMT and the normalization of WM injury may occur during abstinence.     

MEG Coherence and DTI Connectivity in mTLE

Magnetoencephalography (MEG) is a noninvasive imaging method for localization of focal epileptiform activity in patients with epilepsy. Diffusion tensor imaging (DTI) is a noninvasive imaging method for measuring the diffusion properties of the underlying white matter tracts through which epileptiform activity is propagated. This study investigates the relationship between the cerebral functional abnormalities quantified by MEG coherence and structural abnormalities quantified by DTI in mesial temporal lobe epilepsy (mTLE). Resting state MEG data was analyzed using MEG coherence source imaging (MEG-CSI) method to determine the coherence in 54 anatomical sites in 17 adult mTLE patients with surgical resection and Engel class I outcome, and 17 age- and gender- matched controls. DTI tractography identified the fiber tracts passing through these same anatomical sites of the same subjects. Then, DTI nodal degree and laterality index were calculated and compared with the corresponding MEG coherence and laterality index. MEG coherence laterality, after Bonferroni adjustment, showed significant differences for right versus left mTLE in insular cortex and both lateral orbitofrontal and superior temporal gyri (p < 0.017). Likewise, DTI nodal degree laterality, after Bonferroni adjustment, showed significant differences for right versus left mTLE in gyrus rectus, insular cortex, precuneus and superior temporal gyrus (p < 0.017). In insular cortex, MEG coherence laterality correlated with DTI nodal degree laterality (\(R^{2} = 0.46; p = 0.003)\) in the cases of mTLE. None of these anatomical sites showed statistically significant differences in coherence laterality between right and left sides of the controls. Coherence laterality was in agreement with the declared side of epileptogenicity in insular cortex (in 82 % of patients) and both lateral orbitofrontal (88 %) and superior temporal gyri (88 %). Nodal degree laterality was also in agreement with the declared side of epileptogenicity in gyrus rectus (in 88 % of patients), insular cortex (71 %), precuneus (82 %) and superior temporal gyrus (94 %). Combining all significant laterality indices improved the lateralization accuracy to 94 % and 100 % for the coherence and nodal degree laterality indices, respectively. The associated variations in diffusion properties of fiber tracts quantified by DTI and coherence measures quantified by MEG with respect to epileptogenicity possibly reflect the chronic microstructural cerebral changes associated with functional interictal activity. The proposed methodology for using MEG and DTI to investigate diffusion abnormalities related to focal epileptogenicity and propagation may provide a further means of noninvasive lateralization.     

Effects of pioglitazone on diffusion tensor imaging indices in multiple sclerosis patients

Pioglitazone is an FDA-approved peroxisome proliferator activated receptor gamma (PPARγ) agonist. We tested the hypothesis that treatment with pioglitazone reduces new lesion development in patients with RRMS. Twenty-two patients were treated with pioglitazone or placebo and monitored by diffusion tensor imaging (DTI) at baseline and after 12 months. A negative correlation was found between the 1-year change in relative anisotropy (RA) and fluid attenuated inversion recovery (FLAIR) lesion burden in the pioglitazone group. Regions of interest (ROIs) having high ADC and low RA values at baseline had a significantly higher chance to develop into lesions in the placebo group than similar ROIs in the pioglitazone group. These findings suggest that baseline DTI parameters can provide a prognostic surrogate marker for lesions, and that pioglitazone can reduce conversion of normal appearing white matter to lesions.     

磁共振弥散张量成像联合纤维束成像在脑梗死中的应用研究

目的 分析脑梗死患者磁共振弥散张量成像(DTI)和纤维束成像(DTT)的特点,探讨DTI、DTT在对不同时期脑梗死患者诊断的价值。方法分别对58例不同时期脑梗死患者和25名健康志愿者行MRI检查,包括T1WI、T2WI成像、FLAIR及DTI成像,重建部分各向异性(FA)图,对梗死区、健侧相应部位及正常对照组相应部位进...     

磁共振弥散加权成像在鉴别肝脏局灶性良恶性病变中的诊断价值

目的:探讨磁共振(MR)弥散加权成像(DWI)在鉴别肝脏局灶性良恶性病变中的诊断价值。方法:选取83例肝脏局灶性病变患者,全部患者均行常规磁共振成像(MRI)和DWI检查,在DWI检查中选定兴趣区后对病灶不同扩散敏感系数(b值)下的表观弥散系数(ADC值)进行测量,分析肝脏局灶性病变患者的DWI信号表现,对比良恶性病变患者不同b值下的ADC值,以病理结果为参照,比较常规MRI、DWI两种检查方式诊断肝脏局灶性恶性病变的结果,评价诊断效能。结果:83例肝脏局灶性病变患者中恶性病变57例(包括肝转移瘤22例,原发性肝癌35例),良性病变26例(包括肝囊肿12例,肝血管瘤14例),在DWI上原发性肝癌呈高信号或混杂信号,肝转移瘤、肝血管瘤均呈高信号,肝囊肿呈低信号;肝脏局灶性恶性病变高、中、低b值下的ADC值均低于良性病变的ADC值(P0.05);DWI诊断肝脏局灶性恶性病变患者的特异性(96.15%vs 69.23%)、准确性(90.36%vs 72.29%)高于常规MRI(P0.05),误诊率(3.85%vs 30.77%)低于常规MRI(P0.05),DWI诊断肝脏局灶性恶性病变患者的敏感性(87.72%vs 73.68%)、漏诊率(12.28%vs 26.32%)与常规MRI比较无显著差异(P0.05)。结论:在MR鉴别肝脏局灶性良恶性病变中,应用DWI检查可通过比较肝脏局灶性良恶性病变患者的DWI图像信号特征和ADC值判断病变性质,有效提高诊断肝脏局灶性恶性病变患者的特异性和准确性。