Diffusion Tensor Imaging Fiber Research Articles

DTI fiber tractography of human brain

DTI fiber tractography is a powerful tool for investigating the human brain's structural connectivity. It enables us to explore the complex network of fiber pathways that connect different regions of the brain and play a crucial role in its function. In this work, I used DWI(Diffusion-Weighted Imaging) data processing software (such as DiffusionToolkit, and Trackvis ) to construct fiber tracks of the human brain based on MRI(Magnetic Resonance Imaging) data and investigated the brain anatomical structure of a human subject using DTI(Diffusion tensor imaging) fiber tractography. The two software I used was Diffusion Toolkit and Trackvis. Diffusion Toolkit did the preparation work for Trackvis, including data reconstruction and fiber tracking on diffusion-weighted MR(Magnetic Resonance) images. Trackvis was utilized for the tractogram visualization and further analyses of the white matter tracts generated by using DTI fiber tractography. In this work, I successfully used Diffusion Toolkit and Trackvis to construct fiber tracks of the human brain, and the results were correct when compared to the standard brain. Besides, I summarized the principle of DTI and the advantages and disadvantages of the technology.

Cross-hemicord spinal fiber reorganization associates with cortical sensory and motor network expansion in the rat model of hemicontusion cervical spinal cord injury

Magnetic resonance imaging plays an important role in characterizing microstructural changes and reorganization after traumatic injuries to the nervous system. In this study, we tested the feasibility of ex-vivo spinal cord diffusion tensor imaging (DTI) in combination with in vivo brain functional MRI to characterize spinal reorganization and its supraspinal association after a hemicontusion cervical spinal cord injury (SCI). DTI parameters (fractional anisotropy [FA], mean diffusion [MD]) and fiber orientation changes related to reorganization in the contused cervical spinal cord were compared to sham specimens. Altered fiber density and fiber directions occurred across the ipsilateral and contralateral hemicords but with only ipsilateral FA and MD changes. The hemicontusion SCI resulted in ipsilateral fiber breaks, voids and vivid fiber reorientations along the injury epicenter. Fiber directional changes below the injury level were primarily inter-hemispheric, indicating prominent below-level cross-hemispheric reorganization. In vivo resting state functional connectivity of the brain from the respective rats before obtaining the spinal cord samples indicated spatial expansion and increased connectivity strength across both the sensory and motor networks after SCI. The consistency of the neuroplastic changes along the neuraxis (both brain and spinal cord) at the single-subject level, indicates that distinctive reorganizational relationships exist between the spinal cord and the brain post-SCI.

Role of diffusion tensor imaging in stenotic and non-stenotic spinal canal

Background and purposeCervical Spondylotic Myelopathy (CSM) is a gradually escalating spinal cord disturbance set in motion by the degenerative narrowing of the vertebral canal. Routine MRI may fail to detect the subtle early alterations of the cord. MRI Diffusion Tensor Imaging (DTI) possesses the potential to detect these changes. This study intends to estimate the potential of the DTI technique in non-stenotic & stenotic spinal canals in individuals affected with CSM. MethodologySixty-four subjects who met the requirements of the inclusion criteria were incorporated into the investigation. All subjects underwent routine MRI sequences in addition to DTI of the cervical spine region. Scalars such as Fractional Anisotropy (FA), besides Apparent Diffusion Coefficient (ADC), were computed at each cervical intervertebral fibrocartilaginous disc level for all subjects. DTI fiber tractography was then performed to qualitatively assess the microstructural integrity of the tracts. ResultsA noteworthy difference (p<0.05) was seen in the FA parameter and ADC parameter values between the stenotic and non-stenotic groups, with the non-stenotic group having a higher mean FA and a lower ADC than the stenotic group (at the level of stenosis). A significant difference in age was seen between both groups, with most of the patients in the stenotic group belonging to 40 years and above. Tractography helped in demonstrating the morphology of the fiber tracts. ConclusionDTI parameters, namely FA and ADC, are sensitive to damage to the white matter and can be used to detect microstructural changes in the cord. However, standardization of the protocol is necessary when imaging the spinal canal.

A Predictive Visual Analytics System for Studying Neurodegenerative Disease based on DTI Fiber Tracts.

Diffusion tensor imaging (DTI) has been used to study the effects of neurodegenerative diseases on neural pathways, which may lead to more reliable and early diagnosis of these diseases as well as a better understanding of how they affect the brain. We introduce a predictive visual analytics system for studying patient groups based on their labeled DTI fiber tract data and corresponding statistics. The systems machine-learning-augmented interface guides the user through an organized and holistic analysis space, including the statistical feature space, the physical space, and the space of patients over different groups. We use a custom machine learning pipeline to help narrow down this large analysis space and then explore it pragmatically through a range of linked visualizations. We conduct several case studies using DTI and T1-weighted images from the research database of Parkinsons Progression Markers Initiative.

Morphological comparison of masseter muscle fibres in the mandibular rest and open positions using diffusion tensor imaging.

The masseter muscle has a complicated multipennate internal structure and exhibits functional differentiation when performing various stomatognathic functions. It is important to understand the internal structural changes of the muscle during functioning to elucidate characteristic muscle disorders such as local myalgia. Diffusion tensor imaging (DTI) may be useful for investigating the internal structural features of muscle. To evaluate the features of masseter muscle fibres in human participants using DTI fibre tractography, and to elucidate the structural differences in the masseter muscle between the mandibular rest and open positions. Five healthy men (age 31±7years) underwent DTI and T1-weighted MRI of the right masseter muscle in the mandibular rest and open positions. MR images were used as a reference for muscle layer segmentation (superficial, intermediate, and deep). DTI fibre tractography of the masseter muscle was performed and the orientation of the DTI fibres was analysed in each layer using coordinates based on the Frankfurt horizontal plane. The DTI fibre orientation of the deep layer significantly changed between the mandibular rest and open positions in the frontal plane (p<0.05, Wilcoxon rank sum test). However, no significant change was found in the superficial and intermediate layers. DTI fibre tractography confirmed regional differences in the orientation change of the masseter muscle fibres between different mandibular positions. The results may support the existence of functional partitioning inside the masseter muscle and suggest that DTI may be useful for the evaluation of muscle fibres in multipennate muscles.

Bicentric validation of the navigated transcranial magnetic stimulation motor risk stratification model.

The authors sought to validate the navigated transcranial magnetic stimulation (nTMS)-based risk stratification model. The postoperative motor outcome in glioma surgery may be preoperatively predicted based on data derived by nTMS. The tumor-to-tract distance (TTD) and the interhemispheric resting motor threshold (RMT) ratio (as a surrogate parameter for cortical excitability) emerged as major factors related to a new postoperative deficit. In this bicentric study, a consecutive prospectively collected cohort underwent nTMS mapping with diffusion tensor imaging (DTI) fiber tracking of the corticospinal tract prior to surgery of motor eloquent gliomas. The authors analyzed whether the following items were associated with the patient's outcome: patient characteristics, TTD, RMT value, and diffusivity parameters (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]). The authors assessed the validity of the published risk stratification model and derived a new model. A new postoperative motor deficit occurred in 36 of 165 patients (22%), of whom 20 patients still had a deficit after 3 months (13%; n3 months = 152). nTMS-verified infiltration of the motor cortex as well as a TTD ≤ 8 mm were confirmed as risk factors. No new postoperative motor deficit occurred in patients with TTD > 8 mm. In contrast to the previous risk stratification, the RMT ratio was not substantially correlated with the motor outcome, but high RMT values of both the tumorous and healthy hemisphere were associated with worse motor outcome. The FA value was negatively associated with worsening of motor outcome. Accuracy analysis of the final model showed a high negative predictive value (NPV), so the preoperative application may accurately predict the preservation of motor function in particular (day of discharge: sensitivity 47.2%, specificity 90.7%, positive predictive value [PPV] 58.6%, NPV 86.0%; 3 months: sensitivity 85.0%, specificity 78.8%, PPV 37.8%, NPV 97.2%). This bicentric validation analysis further improved the model by adding the FA value of the corticospinal tract, demonstrating the relevance of nTMS/nTMS-based DTI fiber tracking for clinical decision making.

Diffusion Tensor Based White Matter Tract Atlases for Pediatric Populations.

Diffusion Tensor Imaging (DTI) is a non-invasive neuroimaging method that has become the most widely employed MRI modality for investigations of white matter fiber pathways. DTI has proven especially valuable for improving our understanding of normative white matter maturation across the life span and has also been used to index clinical pathology and cognitive function. Despite its increasing popularity, especially in pediatric research, the majority of existing studies examining infant white matter maturation depend on regional or white matter skeleton-based approaches. These methods generally lack the sensitivity and spatial specificity of more advanced functional analysis options that provide information about microstructural properties of white matter along fiber bundles. DTI studies of early postnatal brain development show that profound microstructural and maturational changes take place during the first two years of life. The pattern and rate of these changes vary greatly throughout the brain during this time compared to the rest of the life span. For this reason, appropriate image processing of infant MR imaging requires the use of age-specific reference atlases. This article provides an overview of the pre-processing, atlas building, and the fiber tractography procedures used to generate two atlas resources, one for neonates and one for 1- to 2-year-old populations. Via the UNC-NAMIC DTI Fiber Analysis Framework, our pediatric atlases provide the computational templates necessary for the fully automatic analysis of infant DTI data. To the best of our knowledge, these atlases are the first comprehensive population diffusion fiber atlases in early pediatric ages that are publicly available.

Spectrum-sine interpolation framework for DTI processing.

Diffusion tensor imaging (DTI) data interpolation is important for DTI processing, which could affect the precision and computational complexity in the process of denoising, filtering, regularization, and DTI registration and fiber tracking. In this paper, we propose a novel DTI interpolation framework named with spectrum-sine (SS) focusing on tensor orientation variation in DTI processing. Compared with the state-of-the-art DTI interpolation method using Euler angles or quaternion to represent the orientation of DTI tensors, this method does not need to convert eigenvectors into Euler angles or quaternions, but interpolates each tensor's unit eigenvector directly. The prominent merit of this tensor interpolation method lies in tensor orientation information preservation, which is different from the existing DTI tensor interpolation methods that interpolating tensor's orientation information in a scalar way. The experimental results from both synthetic and real human brain DTI data demonstrated the proposed SS interpolation scheme not only maintains the advantages of Log-Euclidean and Riemannian interpolation frameworks, such as preserving the tensor's symmetric positive definiteness and the monotonic determinant variation, but also preserve the tensor's anisotropy property which was proposed in the spectral quaternion (SQ) method.

Application of Diffusion Tensor Imaging in Obstructive Nephropathy

Background: Obstructive nephropathy is a common clinical disease. Objectives: To explore the value of diffusion tensor imaging (DTI) in obstructive nephropathy. Materials and Methods: Forty healthy Sprague-Dawley (SD) rats were examined in this study. Thirty-two animals underwent complete obstruction of the left ureter, while eight animals underwent a sham surgery. Magnetic resonance imaging (MRI) was performed before surgery and within different intervals after surgery. Eight rats from the experimental group and two rats from the sham group were used in each interval. Following MRI, the animals were sacrificed and sent for medical examinations. The scanning sequences included positioning, transverse T2-weighted (T2W), coronal, and coronal DTI sequences. Image postprocessing was performed after DTI to measure DTI parameters, including apparent diffusion coefficient (ADC) and fractional anisotropy (FA), and to reconstruct DTI fiber traces. One-way analysis of variance was used to compare the parameters between the cortex and medulla and between different intervals. Results: The fiber tracing showed that the obstructed renal fiber bundles were sparse and disordered. The ADC and FA values of the renal cortex, extrarenal medulla, and inner medulla decreased with prolonged hydrops and were negatively correlated with the expression of alpha-smooth muscle actin (α-SMA) and the renal tubulointerstitial lesion grade (r &lt; 0, P &lt; 0.001). Comparison of the cortex, extrarenal medulla, and inner medulla showed the following trends for the ADC and FA values: cortex &gt; extrarenal medulla &gt; inner medulla and cortex &lt; extrarenal medulla &lt; inner medulla, respectively. Conclusions: DTI in obstructive nephropathy not only can reflect the degree of renal interstitial fibrosis and accurately indicate the renal function, but also can provide information regarding renal blood perfusion, water metabolism, and ultrastructural changes.

Computational fluid dynamics simulations for 3D muscle fiber architecture in finite element analysis: Comparisons between computational fluid dynamics and diffusion tensor imaging.

Knowledge of skeletal muscle fiber orientations is important for modeling mechanical properties and behavior of muscle tissue. Diffusion tensor imaging (DTI) may be used to define fiber architecture in vivo but can be expensive and time-consuming and thus impractical for biomechanical modeling applications. Muscle tractography using computational fluid dynamics (CFD) has been shown to determine muscle fiber directions for finite element models in which aponeuroses serve as inlet and outlet boundaries. While the technique is simple to implement, it is unclear which flow simulations and constraints achieve fiber architectures similar to DTI and whether FE simulations based on CFD versus DTI fiber directions produce similar results. Here, we implement CFD tractography on the gastrocnemius muscle using a novel boundary condition method that we developed based on specified inflow direction. We compared results from incompressible potential flow and nondimensionalized incompressible Stokes flow. Comparisons were made between flow methods and results from DTI. Mechanical finite element simulations were subsequently performed on muscle models with fiber directions defined by CFD tractography and DTI. Using our boundary condition method, fiber directions modeled from CFD simulations were similar to DTI. Strain distributions from mechanical simulations were similar between Stokes flow and DTI fiber models. This study demonstrates a new method for specifying inlet boundary conditions that generates physiologically reasonable fiber directions in skeletal muscle. Finite element simulations based on this method are similar to those from DTI, illustrating the ability of CFD to determine muscle fiber architecture for modeling purposes when DTI is not available.

Preoperative nTMS and Intraoperative Neurophysiology - A Comparative Analysis in Patients With Motor-Eloquent Glioma.

BackgroundThe resection of a motor-eloquent glioma should be guided by intraoperative neurophysiological monitoring (IOM) but its interpretation is often difficult and may (unnecessarily) lead to subtotal resection. Navigated transcranial magnetic stimulation (nTMS) combined with diffusion-tensor-imaging (DTI) is able to stratify patients with motor-eloquent lesion preoperatively into high- and low-risk cases with respect to a new motor deficit.ObjectiveTo analyze to what extent preoperative nTMS motor risk stratification can improve the interpretation of IOM phenomena.MethodsIn this monocentric observational study, nTMS motor mapping with DTI fiber tracking of the corticospinal tract was performed before IOM-guided surgery for motor-eloquent gliomas in a prospectively collected cohort from January 2017 to October 2020. Descriptive analyses were performed considering nTMS data (motor cortex infiltration, resting motor threshold (RMT), motor evoked potential (MEP) amplitude, latency) and IOM data (transcranial MEP monitoring, intensity of monopolar subcortical stimulation (SCS), somatosensory evoked potentials) to examine the association with the postoperative motor outcome (assessed at day of discharge and at 3 months).ResultsThirty-seven (56.1%) of 66 patients (27 female) with a median age of 48 years had tumors located in the right hemisphere, with glioblastoma being the most common diagnosis with 39 cases (59.1%). Three patients (4.9%) had a new motor deficit that recovered partially within 3 months and 6 patients had a persistent deterioration (9.8%). The more risk factors of the nTMS risk stratification model (motor cortex infiltration, tumor-tract distance (TTD) ≤8mm, RMTratio <90%/>110%) were detected, the higher was the risk for developing a new postoperative motor deficit, whereas no patient with a TTD >8mm deteriorated. Irreversible MEP amplitude decrease >50% was associated with worse motor outcome in all patients, while a MEP amplitude decrease ≤50% or lower SCS intensities ≤4mA were particularly correlated with a postoperative worsened motor status in nTMS-stratified high-risk cases. No patient had postoperative deterioration of motor function (except one with partial recovery) when intraoperative MEPs remained stable or showed only reversible alterations.ConclusionsThe preoperative nTMS-based risk assessment can help to interpret ambiguous IOM phenomena (such as irreversible MEP amplitude decrease ≤50%) and adjustment of SCS stimulation intensity.

Does motor deficit in children with cerebral palsy correlate with diffusion tensor metrics abnormalities in thalamocortical pathways?

BackgroundCerebral palsy (CP) is a group of motor-impairment signs secondary to many disorders that interfere with early brain development and are usually related to white matter injury in children. Most studies are focused on the study of motor tracts, mainly the corticospinal tract (CST). Diffusion tensor imaging (DTI) is a reliable imaging modality providing an appropriate method of detection of white matter microstructure abnormalities. The purpose of this study is to investigate the relationship between DTI observed motor CST injury, sensory pathways (thalamic radiations) injury, and motor functions.ResultsThis study shows significant involvement (reduction in DTI fiber count) of the superior thalamic radiation (in severe cases) with atrophy of the anterior thalamic radiations (ATR) or posterior thalamic radiations (PTR) in most cases with a significant reduction in fractional anisotropy (FA) and elevation in mean diffusivity (MD) values. In addition, the degree of motor affection shows a significant negative correlation with FA and a significant positive correlation with MD values. Diffusion tensor imaging shows a significant reduction in FA within the examined tracts between CP and control at the Rt CST, Lt CST, Rt corticothalamic radiation (CTR), and Lt CTR with significant cutoff values of ≤ 0.449, ≤ 0.472, ≤ 0.432, and ≤ 0.44, respectively.ConclusionsThis study demonstrates disruption of thalamocortical and corticospinal tracts in CP patients, which reflects that both sensory and motor tract affection have a valuable role in the pathophysiology of motor dysfunction in CP patients.

Functional DTI tractography in brainstem cavernoma surgery

OBJECTIVE Surgical resection of brainstem cavernomas is associated with high postoperative morbidity due to the density of local vulnerable structures. Classical mapping of pathways by diffusion tensor imaging (DTI) has proven to be unspecific and confusing in many cases. In the current study, the authors aimed to establish a more reliable, specific, and objective method for somatotopic visualization of the descending motor pathways with navigated transcranial magnetic stimulation (nTMS)–based DTI fiber tracking. METHODS Twenty-one patients with brainstem cavernomas were examined with nTMS prior to surgery. The resting motor threshold (RMT) and cortical representation areas of hand, leg, and facial function were determined on both hemispheres. Motor evoked potential (MEP)–positive stimulation spots were then set as seed points for tractography. Somatotopic fiber tracking was performed at a fractional anisotropy (FA) value of 75% of the individual FA threshold. RESULTS Mapping of the motor cortex and tract reconstruction for hand, leg, and facial function was successful in all patients. The somatotopy of corticospinal and corticonuclear tracts was also clearly depicted on the brainstem level. Higher preoperative RMT values were associated with a postoperative motor deficit (p &lt; 0.05) and correlated with a lower FA threshold (p &lt; 0.05), revealing structural impairment of the corticospinal tract (CST) prior to surgery. In patients with a new deficit, the distance between the lesion and CST was below 1 mm. CONCLUSIONS nTMS-based fiber tracking enables objective somatotopic tract visualization on the brainstem level and provides a valuable instrument for preoperative planning, intraoperative orientation, and individual risk stratification. nTMS may thus increase the safety of surgical resection of brainstem cavernomas.

Pediatric navigated transcranial magnetic stimulation motor and language mapping combined with diffusion tensor imaging tractography: clinical experience.

In adults, navigated transcranial magnetic stimulation (nTMS) has been established as a preoperative examination method for brain tumors in motor- and language-eloquent locations. However, the clinical relevance of nTMS in children with brain tumors is still unclear. Here, the authors present their initial experience with nTMS-based surgical planning and family counseling in pediatric cases. The authors analyzed the feasibility of nTMS and its influence on counseling and surgical strategy in a prospective study conducted between July 2017 and September 2019. The main inclusion criterion was a potential benefit from functional mapping data derived from nTMS and/or nTMS-enhanced tractography in pediatric patients who presented to the authors' department prior to surgery for lesions close to motor- and/or speech-eloquent areas. The study was undertaken in 14 patients (median age 7 years, 8 males) who presented with different brain lesions. Motor mapping combined with cortical seed area definition could be performed in 10 children (71%) to identify the corticospinal tract by additional diffusion tensor imaging (DTI). All motor mappings could be performed successfully without inducing relevant side effects. In 7 children, nTMS language mapping was performed to detect language-relevant cortical areas and DTI fiber tractography was performed to visualize the individual language network. nTMS examination was not possible in 4 children because of lack of compliance (n = 2), syncope (n = 1), and preexisting implant (n = 1). After successful mapping, the spatial relation between lesion and functional tissue was used for surgical planning in all 10 patients, and 9 children underwent nTMS-DTI integrated neuronavigation. No surgical complications or unexpected neurological deterioration was observed. In all successful nTMS cases, better function-based counseling was offered to the families. In 6 of 10 patients the surgical strategy was adapted according to nTMS data, and in 6 of 10 cases the extent of resection (EOR) was redefined. nTMS and DTI fiber tracking were feasible for the majority of children. Presurgical counseling as well as surgical planning for the approach and EOR were improved by the nTMS examination results. nTMS in combination with DTI fiber tracking can be regarded as beneficial for neurosurgical procedures in eloquent areas in the pediatric population.

Correlation of Clinical Findings in Acute Spinal Injury Patients with Magnetic Resonance Including Diffusion Tensor Imaging and Fiber Tractography.

Introduction Many types of research are being carried out in the fields of understanding of the pathogenesis, early recognition, and improving the outcomes after spinal cord injury (SCI). Diffusion tensor imaging (DTI) is one of the modalities used in vivo microstructural assessment of SCI. The aim of the present study is to evaluate the role of DTI imaging and fiber tractography in acute spinal injury with clinical profile and neurological outcome. Methods The study was carried out on twenty-five patients of acute spinal cord injury who presented within 48 hours of injury and completed minimum of six months follow-up. Results The mean age of patients was 37.32±13.31 years and male & female ratio of 18:7. Total MIS score was 91.64±6.0 initially which improved to 96.92±3.68 after 3 months and 99.4±1.35 after 6 months. Total SIS score was similar at all the time intervals i.e. 224±0. Maximum subjects 14(56%) were classified into AIS C and 5(20%) into AIS D whereas only 6(24%) subjects were having no deficit (AIS E). At the end of 6 months, 13(52%) subjects had no deficit (AIS E). Mean fractional anisotropy (FA) initially was 0.451 (± 0.120) but after 6 months, it increased to 0.482 (± 0.097) (p<0.001). The mean apparent diffusion coefficient (ADC) initially was 3.13 (± 2.68) but after 6 months, it decreased to 3.06 (± 2.68) and this change was found to be statistically highly significant (p<0.001). Mean anisotropy index (AI) initially was 0.420 (± 0.245) but after 6 months, it increased to 0.430 (± 3.41) and this change was found to be statistically significant (p<0.01). Conclusions DTI is a sensitive tool to detect neurological damage in SCI and subsequent neurological recovery. FA correlated with ASIA impairment scale. It can be useful as an adjunct to conventional MRI for better evaluation and predicting prognosis in SCI patients.

Third-trimester in utero fetal brain diffusion tensor imaging fiber tractography: a prospective longitudinal characterization of normal white matter tract development.

White matter is responsible for inter-neuronal connections throughout the brain that are a driving force in cognitive development. Diffusion tensor imaging (DTI) fiber tractography has been used to evaluate white matter development in the fetal brain; however, longitudinal studies of DTI fiber tractography to assess white matter development in the third trimester are lacking. To characterize in utero longitudinal changes in the fetal brain DTI fiber tracts of normal third-trimester fetuses. For this single-center prospective longitudinal observational pilot study, we recruited 28 pregnant females with normal third-trimester pregnancies who had routine prenatal ultrasound. MRI of the in utero fetal brain was performed with a Siemens 1.5-tesla (T) Espree scanner at 31weeks, 33weeks and 36weeks of gestation, with 14 DTI tractography parameters quantified in 7 brain regions using DTI-studio version 2.4 (Johns Hopkins University, Baltimore, MD; n=98 measurements). We used multilevel mixed models to examine the relationship between longitudinal changes in DTI measurements and between 98 DTI measurements at 31weeks and 4 routine fetal brain anatomical biometrics (n=392 assessments). We observed statistically significant decreases in radial diffusivity and apparent diffusion coefficient in 13 of 14 brain regions from 31weeks to 36weeks of gestation (P<0.001 for all regions except the genu of the corpus callosum). Significant decreases in radial diffusivity from weeks 33 to 36 and weeks 31 to 36 were seen in the corticospinal tracts, centrum semiovale, posterior limb of the internal capsule, and crus cerebri (P<0.001 for all). When considering all possible combinations of DTI fiber tract measurements and the routine morphological fetal brain biometrics, only 6% (24/392) had a significant association (P<0.05), indicating relative independence of the DTI fiber tract measurements from anatomical biometrics. In utero longitudinal changes in fetal brain DTI fiber tractography are quantifiable in normal third-trimester fetuses and are largely independent of morphological brain changes.

Correlation between the Position of the Pituitary Stalk as Determined by Diffusion Tensor Imaging and Its Location as Determined at the Time of Surgical Resection of Pituitary Adenomas

ObjectiveAn important factor during pituitary adenoma surgery is to preserve pituitary stalk (PS) as this plays a role in reduction of the risk of postoperative diabetes insipidus. The hypothalamic-hypophyseal tract (HHT) projects through the PS to the posterior pituitary gland. To reconstruct white matter fiber pathways, methods like diffusion tensor imaging (DTI) tractography have been widely used. In this report we attempted to predict the position of PS using DTI tractography and to assess its intraoperative correlation during surgery of pituitary adenomas. MethodsDTI tractography was used to tract the HHT in nine patients before craniotomy for pituitary adenomas. The DTI location of the HHT was compared with the PS position identified at the time of surgery. DTI fiber tracking was carried out in nine patients prior to the planned craniotomy for pituitary adenomas. In one patient, the PS could not be identified during the surgery. In the other eight patients, a comparison was made between the location of the HHT identified by DTI and the position of the PS visualized at the time of surgery. ResultsThe position of the HHT identified by DTI showed consistency with the intraoperative position of the PS in seven patients (88.9% concordance). ConclusionThis study shows that DTI can identify the position of the HHT and thus the position of the PS with a high degree of reliability.

Interactive Diffusion Tensor Imaging Fiber Data Visualization Via Leap Motion

Diffusion Tensor Imaging (DTI) reveals subtle abnormalities associated with stroke, multiple sclerosis, schizophrenia and dyslexia, which has a broad application prospect in the medical field. The densely sampled 3-D DTI fiber tracts in biological specimens have high geometric, spatial and anatomical complexity. To provide users with more immersive and convenient interactions in exploring DTI fibers, we design specific interactions based on the APIs of Leap Motion. Leap Motion is a somatosensory interaction device focusing on hand tracking. We design four different interaction modes for users to analyze the data in different interaction stages and scenarios, in order to better explore the DTI fibers which users are interested in by Leap Motion gestures. They are Normal Mode , Box Basic Interaction Mode , Box Logic Operation Mode , and Cluster Exploration Mode . Users can conduct tradition manipulations over the whole DTI fiber data in Normal Mode . Boxes are employed to filter out uninteresting tracts in Box Basic Interaction Mode , and expression-based queries are further designed to get logic set operations based on multiple boxes in Box Logic Operation Mode , e.g., the intersection, union and complement of boxes. Complex logic combination queries are allowed to perform to reduce visual clutter and help users explore DTI fibers more precisely. In Cluster Exploration Mode , DTI fibers can be classified by clustering them into spatially and anatomically related tracts and then different clusters can be explored individually by designed gestures. Compared with the explorations through traditional input devices, the evaluation tests show that the proposed approach is more intuitive and efficient in 3-D explorations and provides an immersive experience for users to explore the DTI fiber data.

Augmented Reality with Diffusion Tensor Imaging and Tractography during Laparoscopic Myomectomies

Augmented reality is a technology that allows a surgeon to see key hidden subsurface structures in an endoscopic video in real-time. This works by overlaying information obtained from preoperative imaging and fusing it in real-time with the endoscopic image. Magnetic resonance diffusion tensor imaging (DTI) and fiber tractography are known to provide additional information to that obtained from standard structural magnetic resonance imaging (MRI). Here, we report the first 2 cases of the use of real-time augmented reality during laparoscopic myomectomies with visualization of uterine muscle fibers after DTI tractography–MRI to help the surgeon decide the starting point incision.In the first case, a 31-year-old patient was undergoing laparoscopic surgery for a 6-cm FIGO type V myoma. In the second case, a 38-year-old patient was undergoing a laparoscopic myomectomy for a unique 6-cm FIGO type VI myoma. Signed consent forms were obtained from both patients, which included clauses of no modification of the surgery. Before surgery, MRI was performed. The external surface of the uterus, the uterine cavity, and the surface of the myomas were delimited on the basis of the findings of preoperative MRI. A fiber tracking algorithm was used to extrapolate the uterine muscle fibers’ architecture.The aligned models were blended with each video frame to give the impression that the uterus is almost transparent, enabling the surgeon to localize the myomas and uterine cavity exactly. The uterine muscle fibers were also displayed, and their visualization helped us decide the starting incision point for the myomectomies. Then, myomectomies were performed using a classic laparoscopic technique.These case reports show that augmented reality and DTI fiber tracking in a uterus with myomas are possible, providing fiber direction and helping the surgeon visualize and decide the starting incision point for laparoscopic myomectomy. Respecting the fibers’ orientation could improve the quality of the scar and decrease the architectural disorganization of the uterus.

Benefits of MR Diffusion Tensor Imaging and Fiber Tractography Over Conventional MRI in Preoperative Evaluation of Pediatric Brain Tumors

AbstractBackground: Diffusion tensor imaging (DTI) is a nonin-vasive magnetic resonance imaging (MRI) modality which accurately shows the location and orientation of subcortical white matter (WM) tracts. The surgeon benefits from DTI as it depicts the relationship of the intra-axial tumor to local WM tracts in multiple planes.Aim of Study: The purpose of this study is to evaluate the role of MR diffusion tensor imaging and fiber tractography and its benefits over conventional MRI in accurate preoperative localization of important eloquent areas in pediatric brain tissue and their relation to the brain tumor. The aim of the study is to help the surgeon in planning his surgical corridor which causes the least damage and minimizes the postoperative neurological deficits.Patients and Methods: A total of fifty patients with brain tumors were included in this study using pre-operative contrast-enhanced magnetic resonance imaging and DTI fiber tractog-raphy for preoperative localization of important white matter tracts. Diffusion tensor imaging, by improving the recognition and characterization of white matter tracts, offers a glimpse into the brain microstructure at a scale that is not easily accessible with other modalities.Results: The extent of white matter pathway involvement was clearly identified in all patients by using color-coded DT imaging maps and MR Tractography.The study revealed that the most common tract involve-ment pattern detected was pattern (displacement). It was seen in 36 cases representing 72% of all cases. Pattern I (not affected) was detected in 6 cases representing 12%. Pattern III (edematous) was detected in 11 cases representing 22%. Pattern IV (partially disrupted) was detected in 13 cases representing 26%. Pattern V (destroyed) was detected in 3 cases representing 6%. Combined pattern of affection has been detected in most of the cases.Conclusion: The effect of cerebral neoplasms on white matter pathways is not precisely understood with the aid of standard diagnostic modalities. Diffusion-tensor imaging allowed for the preoperative identification of white matter pathways involved by tumor but the preoperative planning should be optimally complemented by various intraoperative procedures in order to insure a good neurological outcome of the surgery and valid functional prognosis.