Application of Magnetic Resonance Diffusion Tensor Imaging in Diagnosis of Lumbosacral Nerve Root Compression

OBJECTIVE: The aim of this study was to assess the value of 3.0T magnetic resonance (MR) Diffusion tensor imaging (DTI) in the diagnosis of lumbosacral nerve root compression. METHODS: The radiology reports, and clinical records of 34 patients with nerve root compression caused by lumbar disc herniation or bulging and 21 healthy volunteers who had undergone magnetic resonance imaging (MRI) and DTI scan were retrospectively reviewed. The differences in fractional anisotropy (FA) and apparent diffusion coefficient (ADC) between compressed and non-compressed nerve roots from patients and the normal nerve roots from healthy volunteers were compared. Meanwhile, the nerve root fiber bundles were observed and analyzed. RESULTS: The average FA and ADC values of the compressed nerve roots were 0.254 ± 0.307 and 1.892 ± 0.346 10^-3mm2/s, respectively. The average FA and ADC values of the non-compressed nerve roots were 0.377 ± 0.659 and 1.353 ± 0.344 10^-3mm2/s, respectively. The FA value of compressed nerve roots was significantly lower than that of non-compressed nerve roots (P < 0.01). The ADC value of compressed nerve roots was significantly higher than that of non-compressed nerve roots. There were no significant differences between the left and right nerve roots of normal volunteers in FA and ADC values (P > 0.05). The nerve roots at different levels of L3-S1 had significantly different FA and ADC values (P < 0.01). Incomplete fiber bundles with extrusion deformation, displacement or partial defect were observed in the compressed nerve root fiber bundles. The real diagnosis of the clinical situation of the nerve can provide neuroscientists with an important computer tool to help them infer and understand the possible working mechanism from the experimental data of behavior and electrophysiology. CONCLUSION: The compressed lumbosacral nerve roots can be accurately localized through 3.0T magnetic resonance DTI, which is instructive for accurate clinical diagnosis and preoperative localization.

Diffusion tensor imaging of the hippocampus reflects the severity of hippocampal injury induced by global cerebral ischemia/reperfusion injury.

At present, predicting the severity of brain injury caused by global cerebral ischemia/reperfusion injury (GCI/RI) is a clinical problem. After such an injury, clinical indicators that can directly reflect neurological dysfunction are lacking. The change in hippocampal microstructure is the key to memory formation and consolidation. Diffusion tensor imaging is a highly sensitive tool for visualizing injury to hippocampal microstructure. Although hippocampal microstructure, brain-derived neurotrophic factor (BDNF), and tropomyosin-related kinase B (TrkB) levels are closely related to nerve injury and the repair process after GCI/RI, whether these indicators can reflect the severity of such hippocampal injury remains unknown. To address this issue, we established rat models of GCI/RI using the four-vessel occlusion method. Diffusion tensor imaging parameters, BDNF, and TrkB levels were correlated with modified neurological severity scores. The results revealed that after GCI/RI, while neurological function was not related to BDNF and TrkB levels, it was related to hippocampal fractional anisotropy. These findings suggest that hippocampal fractional anisotropy can reflect the severity of hippocampal injury after global GCI/RI. The study was approved by the Institutional Animal Care and Use Committee of Capital Medical University, China (approval No. AEEI-2015-139) on November 9, 2015.

Diffusion tensor imaging study of brain precentral gyrus and postcentral gyrus during normal brain aging process.

OBJECTIVE: To study the changes of white matter tracts in precentral gyrus and postcentral gyrus during normal brain aging process by analyzing fractional anisotropy (FA) values obtained from diffusion tensor imaging (DTI) technology. METHODS: Magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were conducted on 120 healthy right-handed subjects. The subjects were separated into four age groups, namely Young Male/Female (<45 years old) and Senior Male/Female (>45 years old). Each subject undertakes routine MRI and DTI scans. Left/right precentral and left/right postcentral gyrus are automatically detected on the image. The area for region of interest (ROI) is set to be 18 ± 2 mm2 . RESULTS: For each age group, the FA values of white matter in precentral gyrus and postcentral gyrus are statistically different (p < .05) in both left and right sides of the brain across different age groups and genders. Additionally, the FA values are statistically different (p < .05) between two young and senior age groups across different genders, brain regions, and hemispheres. CONCLUSION: The FA values of precentral gyrus and postcentral gyrus are statistically different across genders, age groups, and hemispheres. Additionally, the FA values of both precentral gyrus and postcentral gyrus decrease over time, which is a strong indication of aging.

White matter abnormalities in depression: A categorical and phenotypic diffusion MRI study.

Mood depressive disorder is one of the most disabling chronic diseases with a high rate of everyday life disability that affects 350 million people around the world. Recent advances in neuroimaging have reported widespread structural abnormalities, suggesting a dysfunctional frontal-limbic circuit involved in the pathophysiological mechanisms of depression. However, a variety of different white matter regions has been implicated and is sought to suffer from lack of reproducibility of such categorical-based biomarkers. These inconsistent results might be attributed to various factors: actual categorical definition of depression as well as clinical phenotype variability. In this study, we 1/ examined WM changes in a large cohort (114 patients) compared to a healthy control group and 2/ sought to identify specific WM alterations in relation to specific depressive phenotypes such as anhedonia (i.e. lack of pleasure), anxiety and psychomotor retardation -three core symptoms involved in depression. Consistent with previous studies, reduced white matter was observed in the genu of the corpus callosum extending to the inferior fasciculus and posterior thalamic radiation, confirming a frontal-limbic circuit abnormality. Our analysis also reported other patterns of increased fractional anisotropy and axial diffusivity as well as decreased apparent diffusion coefficient and radial diffusivity in the splenium of the corpus callosum and posterior limb of the internal capsule. Moreover, a positive correlation between FA and anhedonia was found in the superior longitudinal fasciculus as well as a negative correlation in the cingulum. Then, the analysis of the anxiety and diffusion metric revealed that increased anxiety was associated with greater FA values in genu and splenium of corpus callosum, anterior corona radiata and posterior thalamic radiation. Finally, the motor retardation analysis showed a correlation between increased Widlöcher depressive retardation scale scores and reduced FA in the body and genu of the corpus callosum, fornix, and superior striatum. Through this twofold approach (categorical and phenotypic), this study has underlined the need to move forward to a symptom-based research area of biomarkers, which help to understand the pathophysiology of mood depressive disorders and to stratify precise phenotypes of depression with targeted therapeutic strategies.

Diffusion tensor imaging to assess recovery of white matter injury in periventricular leucomalacia with cerebral palsy after surgery / 实用放射学杂志

Objective To discuss the value of DTI on recovery of white matter injury in periventricular leucomalacia (PVL) with cerebral palsy after surgery.Methods 15 childrens suffered from PVL and 15 age-matched normal controls with normal MRI findings and no neurological abnormalities were recruited in this study.Conventional plain MRI scans and DTI sequence of brain were preformed in all subjects.FA maps of eight selected regions,which included the corpus callosum genu,splenium of corpus callosum,bilateral anterior limb of internal capsule,bilateral posterior limb of internal capsule,bilateral optic radiation,bilateral cerebral pedunculusand superior longitudinal fasciculus were compared between two groups.Results Significant differences of FA values were observed among the three group before and after the treatment and control groups(P＜0.05).FA value of the caudate nucleus and lenticular nucleus among three group was not statistically significant difference.Further pairwise comparison,FA values of the posterior limb of internal capsul,genu of corpus callosum and splenium of corpus callosum in three groups showed statistically significant differences,there was no statistically significant difference for FA value of the genu of capsulae internae,cerebral peduncle and pons among the three group.Compared to the contralateral normal areas,FA value of the genu of capsulae internae,cerebral peduncle and pons showed statistically significant differences (P＜0.05).Conclusion Quantitative DTI may show subtle changes in the structure of white matter,which has a certain reference value of FA values of white matter in periventricular leucomalacia with cerebral palsy after surgery,and help clinicians further reasonable treatment.

Basic Principle and Image Analysis in the Diffusion Tensor Image.

The magnetic resonance imaging (MRI) is established as the imaging technique that is essential to the imaging of the central nervous system disease. Above all, the diffusion weighted image (DWI) is known as the tool which can diagnose acute ischemic stroke with high accuracy in a short time. DTI, an applied form of DWI, was devised as a technique to image the structure of the brain white matter. In clinical sites, this technique is used for pathologic elucidation such as the intracerebral tissue injury or mental disorder. Additionally, diffusion tensor tractography (DTT), which is a technique to build three-dimensional structure of the neural fiber tracts, is used for grasping the relations between a brain tumor and the fibers tract. Therefore, these techniques may be useful imaging tools in the central nerve region.

Normal-appearing white matter in children with developmental delay:a diffusion tensor imaging study / 实用放射学杂志

Objective To explore the changes of white matter microstructure by using DTI in children with developmental delay (DD)with normal routine MRI results.Methods We performed routine MRI and DTI in 23 children with DD and 23 age-matched normal children,FA values of five deep white matters (limb of internal capsule,anterior limb,genu and knee of corpus callosum and optic radiation)and four shallow white matters (frontal lobe,temporal lobe,occipital cortex,centrum ovale)were measured.FA values of the white matter for two groups were assessed by paired t tests for each region of interest.Results FA values on the deep white matter for DD,and on the deep white matter and the shallow white matter for normal development group increased with age significantly (P 0.05).The FA values on the shallow white matter and deep white matter (corpus callo-sum knee,optic radiation)for children with DD were lower than that for the control group (P 0.05).Conclusion DTI may detect the changes of white matter microstructure in children with developmental delay,and provides an objective basis for quantitative diagnosis.