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.

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.

Traumatic axonal injury of the cingulum in patients with mild traumatic brain injury: a diffusion tensor tractography study

The cingulum,connecting the orbitofrontal cortex to the medial temporal lobe,involves in diverse cognition functions including attention,memory,and motivation.To investigate the relationship between the cingulum injury and cognitive impairment in patients with chronic mild traumatic brain injury,we evaluated the integrity between the anterior cingulum and the basal forebrain using diffusion tensor tractography in 73 patients with chronic mild traumatic brain injury(39 males,34 females,age 43.29±11.42 years)and 40 healthy controls(22 males,18 females,age 40.11±16.81 years).The patients were divided into three subgroups based on the integrity between the anterior cingulum and the basal forebrain on diffusion tensor tractography:subgroup A(n=19 patients)– both sides of the anterior cingulum were intact;subgroup B(n=36 patients)– either side of the anterior cingulum was intact;and subgroup C(18 patients)– both sides of the anterior cingulum were discontinued.There were significant differences in total Memory Assessment Scale score between subgroups A and B and between subgroups A and C.There were no significant differences in diffusion tensor tractography parameters(fractional anisotropy,apparent diffusion coefficient,and fiber volume)between patients and controls.These findings suggest that the integrity between the anterior cingulum and the basal forebrain,but not diffusion tensor tractography parameter,can be used to predict the cognitive function of patients with chronic mild traumatic brain injury.This study was approved by Yeungnam University Hospital Institutional Review Board(approval No.YUMC-2014-01-425-010)on August 16,2017.

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.

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.

Diffusion tensor tractography of the arcuate fasciculus in patients with brain tumors: Comparison between deterministic and probabilistic models

Purpose: The purpose of this study was to compare the deterministic and probabilistic tracking methods of diffusion tensor white matter fiber tractography in patients with brain tumors. Materials and Methods: We identified 29 patients with left brain tumors ciculus was reconstructed using a deterministic Fiber Assignment by Continuous Tracking (FACT) algorithm and a probabilistic method based on an extended Monte Carlo Random Walk algorithm. Tracking was controlled using two ROIs corresponding to Broca’s and Wernicke’s areas. Tracts in tumoraffected hemispheres were examined for extension between Broca’s and Wernicke’s areas, anterior-posterior length and volume, and compared with the normal contralateral tracts. Results: Probabilistic tracts displayed more complete anterior extension to Broca’s area than did FACT tracts on the tumor-affected and normal sides (p rs.

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.

Motor recovery via aberrant pyramidal tract in a patient with traumatic brain injury A diffusion tensor tractography study

The aberrant pyramidal tract is the collateral pathway of the pyramidal tract through the medial lemniscus in the brainstem. A 21-year-old man presented with right hemiparesis due to a traumatic intracerebral hemorrhage in the left corona radiata. His motor function recovered almost to the normal state at 10 months after onset. Through diffusion tensor tractography, the pyramidal tract in the affected （left） hemisphere showed discontinuation at the pontine level at 13 months after onset. An aberrant pyramidal tract was observed, which originated from the primary motor cortex and the supplementary motor area and descended through the corona radiata, then through the posterior limb of the internal capsule and the medial lemniscus pathway from the midbrain to the pons, finally entered into the pyramidal tract area at the pontomedullary junction, it suggests that the motor functions of the right extremities in this patient had recovered by this aberrant pyramidal tract.

Aberrant pyramidal tract in a patient with corona radiata infarct A diffusion tensor tractography study

The aberrant pyramidal tract refers to the collateral pathway of the pyramidal tract through the medial lemniscus in the brainstem. A 63-year-old male patient presented with severe paralysis of the left extremities due to a right corona radiata infarct. He was able to extend the affected fingers against resistance at 2 months after stroke onset. At 6 months after stroke onset, he was able to perform some fine motor activities, as well as to walk with a nearly normal gait. Functional MRI, which was performed at 6 months after onset, showed that the contralateral primary sensorimotor cortex was activated during affected （left） hand movements. Diffusion tensor tractography results showed that at 2 weeks after stroke onset, pyramidal tracts of the affected hemisphere originated from the primary motor cortex and descended along the known pathway of the pyramidal tract with an aberrant pyramidal tract, which was bypassed through the medial lemniscus from the midbrain to the lower pons. However, the pyramidal tract from midbrain to pons in the affected hemisphere could not be depicted by diffusion tensor tractography at 6 months after stroke onset; instead, only the aberrant pyramidal tract existed for the course of the disappeared pyramidal tract. Results from this study indicate that the main motor functions of the affected extremities appeared to be controlled via the aberrant pyramidal tract with degeneration of the pyramidal tract in the brainstem of the affected hemisphere.

Impaired consciousness caused by injury of the lower ascending reticular activating system: evaluation by diffusion tensor tractography

A 34-year-old male patient underwent conservative management for traumatic hemorrhage in the right frontal lobe（Figure 1A）.The patient lost consciousness for approximately 4 weeks and experienced post-traumatic amnesia continuously from the time of the accident.The patient’s Glasgow Coma Scale score（Teasdale et al.,1974）was 6

Diffusion tensor tractography studies on mechanisms of recovery of injured fornix

The fornix,which connects the medial temporal lobe and the medial diencephalon,is involved in episodic memory as an important part of the Papez circuit.The mechanisms of recovery of an injured fornix revealed by diffusion tensor tractography in the five studies are summarized as follows：1） recovery through the nerve tract from an injured fornical crus to the medial temporal lobe via the normal pathway of the fornical crus;2）recovery through the nerve tract originating from an ipsi-lesional fornical body connected to the ipsi-lesional medial temporal lobe via the splenium of the corpus callosum;3） recovery through the nerve tract from the ipsi-lesional fornical body extending to the contra-lesional medial temporal lobe via the splenium of the corpus callosum;4） recovery through the nerve tract originating from the ipsi-lesional fornical column connected to the ipsi-lesional medial temporal lobe;and 5） recovery through the nerve tract originating from the contra-lesional fornical column connected to the ipsi-lesional medial temporal lobe via the contra-lesional medial temporal lobe and the splenium of the corpus callosum.These diffusion tensor tractography studies on mechanisms of recovery of injured fornical crus appeared to provide useful information for clinicians caring for patients with brain injury,however,studies on this topic are still in the beginning stages.

Recovery of cerebellar peduncle injury in a patient with a cerebellar tumor: validation by diffusion tensor tractography

The cerebellum has a complex network and relates to various clinical functions including ataxia, gait disturbance, hearing and vision, cognition and affective control. Cerebellar peduncles are the structure connecting the cerebellum to the brain stem and the cerebrum. There exist three cerebellar peduncles. The superior cerebellar peduncle （SCP） involves vestibular sense and proprio- ception connecting to the thalamocortical pathway. The middle cerebellar peduncle （MCP） is the largest structure among the three cerebellar peduncles conveying impulses from the cerebral cortex to the cerebellum through corticopontocerebellar tract.

Compression of the bilateral corticospinal tracts by bilateral pontine hemorrhage A diffusion tensor tractography study

Bilateral spontaneous pontine hemorrhage is rare. In addition, bilateral corticospinal tract （CST） involvement in the pons may accompany serious motor sequelae. A 45-year-old right-handed woman was admitted for bilateral pontine hemorrhage. The patient presented with moderate quadriparesis at stroke onset and quickly recovered to the point of being able to extend the muscles of all four extremities against resistance, at 2 weeks from onset. At 4 weeks after stroke onset, she was able to perform all fine motor activities, as well as to walk with a normal gait. Diffusion tensor tractography results showed that the CSTs of both hemispheres originated from the primary sensorimotor cortex and descended through the corona radiata, the posterior limb of the internal capsule, midbrain, anterior pons, and the anterior medulla, along the known pathway of the CST. However, at midbrain and pons, the CSTs were compressed posterolaterally. The contralateral primary sensorimotor cortex, centered on the precentral knob, was activated during movement of either hand of the patient, as shown by functional MRI, which indicates the preservation of lateral CST. Findings from this study suggest that diffusion tensor tractography may be helpful in the elucidation of the CST status in patients with pontine hemorrhage.

Curvature range measurements of the arcuate fasciculus using diffusion tensor tractography

Because Broca＇s area and Wernicke＇s area in the brain are connected by the arcuate fasciculus, understanding the anatomical location and morphometry of the arcuate fasciculus can help in the treatment of patients with aphasia. We measured the horizontal and vertical curvature ranges of the arcuate fasciculus in both hemispheres in 12 healthy subjects using diffusion tensor tractography. In the right hemisphere, the direct curvature range and indirect curvature range values of the arcuate fasciculus horizontal part were 121.13 ± 5.89 and 25.99 ± 3.01 degrees, respectively, and in the left hemisphere, the values were 121.83 ± 5.33 and 27.40 ± 2.96 degrees, respectively. In the right hemisphere, the direct curvature range and indirect curvature range values of the arcuate fasciculus vertical part were 43.97 ± 7.98 and 30.15 ± 3.82 degrees, respectively, and in the left hemisphere, the values were 39.39 ± 4.42 and 24.08 ± 4.34 degrees, respectively. We believe that the measured curvature ranges are important data for localization and quantitative assessment of specific neuronal pathways in patients presenting with arcuate fasciculus abnormalities.

Weak phonation due to unknown injury of the corticobulbar tract in a patient with mild traumatic brain injury: a diffusion tensor tractography study

In this study,we report on a patient who showed weak phonation following mild traumatic brain injury（TBI）,which was demonstrated by diffusion tensor tractography（DTT）.

Cost Analysis of Diffusion Tensor Imaging and MR Tractography of the Brain

Purpose: To determine the total direct costs (fixed and variable costs) of diffusion tensor imaging (DTI) and MR tractography reconstruction of the brain. Materials and Methods: The direct fixed and variable costs of DTI with MR tractography were determined prospectively with time and motion analysis in a 1.5-Tesla MR scanner using 15 encoding directions. Seventeen patients with seizure disorders, 9 males & 8 females, with mean age of 13 years (age range 2 - 33 years) were studied. Total direct costs were calculated from all direct fixed and variable costs. Sensitivity analyses between 1.5 versus a 3-Tesla MR system, and 15 versus 32 encoding directions were done. Results: The total direct costs of DTI and MR tractography for a 1.5-T system with 15 encoding directions were US $97. Variable cost was $76.80 and fixed cost was $20.20. Total direct costs for a 3-T system with 15 directions decreased to US $94.5 because of the shorter scan time despite the higher cost of the 3-T system. The most costly component of the direct cost was post-processing analysis at US $46.00. Conclusion: DTI with MR tractography has important total direct costs with variable costs higher than the fixed costs. The post processing variable cost is the most expensive component. Developing more accurate automated post-processing software for DTI and MR tractography is important to decrease this variable labor cost. Given the added value of DTI-MR tractography and the costs involved reimbursement codes should be considered.

Recovery of the corticospinal tracts injured by subfalcine herniation: a diffusion tensor tractography study

Motor weakness is one of the most serious disabling sequelae of stroke. For successful rehabilitation, thorough estimation of the state of injured neural tracts for motor function is mandatory. After development of diffusion tensor tractogra- phy （DTT）, which is derived from diffusion tensor imaging （DTI）, three-dimensional reconstruction and estimation for three motor tracts, such as the corticospinal tract, the rubrospinal tract, and the corticoreticular pathway became possible （Kunimatsu et al., 2004; Puig et al., 2010; Yang et al., 2011）. The corticospinal tract is known to be a major neural tract for motor function in the human brain （Binkofski et al., 1996）.

Improved Visualization of the Anterior Thalamic Radiation in Bipolar Disorder by Diffusion Tensor Tractography

Diffusion tensor imaging (DTI) is a method for noninvasively measuring and imaging the diffusion of water molecules using MRI. Diffusion tensor tractography (DTT) can be used to presume macroscopic nerve fascicle distribution by determining, based on information obtained by DTI, whether the diffusion anisotropy vectors of adjacent voxels are continuous or not. We prepared a DTT map of the cerebral white matter nerve fascicles and investigated its usefulness for differentiation between Alzheimer’s disease and bipolar disorder (BD), a major depressive disorder, based on the nerve fiber depiction, in addition to the fractional anisotropy and apparent diffusion coefficient values. We encountered two cases of BD in which the DTT image of the anterior thalamic radiation (ATR) improved following effective treatment with lamotrigine. Lamotrigine increases the synaptic strength due to its effect of promoting the traffic of the α-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor on the neuronal membrane. Downregulation of postsynaptic AMPA receptor expression can reportedly be observed during depressive episodes in BD. We consider that visualization of improvement of the ATR in response to treatment with lamotrigine (related to its pharmacological effect on the AMPA receptor) is valuable, as it suggests reversibility of the damage of the nerve fibers in this disease condition.

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）.

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.