DTI-derived Parameters Research Articles

Diffusion tensor imaging identifies atrial regional changes associated with atrial fibrillation remodelling

Abstract Background Structural remodeling in the context of persistent atrial fibrillation (PAF) has been mainly characterized by imaging techniques focused on fibrosis detection. Diffusion tensor imaging (DTI) has demonstrated its direct relationship with histological properties and myocyte organization, which may provide a more complete structural information. However, the potential of DTI in the characterization of the AF-related structural substrate remains unknown. Purposes To evaluate the performance of DTI-derived parameters to characterise the structural remodelling derived from persistent AF and its relationship with specific atrial regions associated with AF maintenance (i.e., driver regions). Methods Two experimental groups of pigs were studied: control (n=7) and PAF (n=10). The PAF swine model was developed using rapid atrial pacing until the animals reached a stage of self-sustained PAF. The AV node was ablated to prevent heart failure due to fast ventricular activation rates. A second lead in the right ventricular was used for ventricular pacing at 60-110 bpm. Animals with PAF were studied after ≥ 6 months in self-sustained persistent AF. AF animals underwent invasive electroanatomical to identify driver regions based on instantaneous frequency modulation maps. After euthanasia, explanted hearts from AF animals and controls underwent DTI including 15 diffusion weighted images with a b-value of 600 s/mm² plus a non-DWI volume (isotropic resolution, 0.6 mm³). DTI images were segmented and divided into 13 atrial anatomical regions. Driver regions in AF animals were also segmented and classified as functional regions of interest (ROIs) (Figure 2B). Afterwards, diffusion tensors were estimated and scalar features were analyzed (Figures 1A and 2A) according to both anatomical and functional ROIs. Results DTI analysis in AF animals revealed region-specific structural remodelling (Figure 1B). Compared to controls, PAF animals showed an increased fractional anisotropy (FA) in both right and left atrial free walls (Figure 1C). Other anatomical regions, such as the superior vena cava (SVC), the coronary sinus (CS) or the left atrium roof developed higher axial diffusivities in AF compared to controls (Figure 1D), without significant alterations in FA (Figure 1C). AF driver regions were frequently located in the CS, the SVC and the LAA (Figure 2C). AF driver ROIs into the CS and the SVC showed intracase increased diffusivities and decreased linear indexes compared to non-driver regions. However, AF driver ROIs in the LAA showed increased intervoxel main eigenvector dispersion in contrast to non-driver ROIs (Figure 2C). Conclusion DTI sequences provide atrial structural information associated with functional tissue properties relevant for AF maintenance.

Alterations in Diffusion Tensor Imaging-derived Indices of Auditory Pathway-related Fiber Tracts in Children With Sensorineural Hearing Loss.

Hearing loss is the most common sensory-neurological defect in humans. The most common hearing impairment is sensorineural hearing loss (SNHL) caused by the inner ear and related nerves. Diffusion tensor imaging (DTI) is an advanced MRI technique that can provide valuable information about auditory neural pathways and their microstructural changes. The present study was designed to investigate the microstructural changes in auditory pathways-related fiber tracts in children with SNHL. Twenty-two children including 11 subjects with SNHL aged 1-4 years and 11 healthy children were examined as controls. Then, DTI-derived parameters, such as fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AxD), and radial diffusivity (RD), and volume of fiber tracts were extracted from the inferior longitudinal fasciculus, acoustic radiation, and uncinate fasciculus. The results showed an increase in MD, RD, and AxD as well as a decrease in FA, volume, and diameter of auditory-pathway-related fiber tracts. Interestingly, there was an increase in the FA of acoustic radiation. White matter connections in the auditory canal decrease and AR integrity increases due to compensatory effects. These probably reflect atrophy or degradation as well as compensatory cross-modal reorganization in the absence of auditory input and the use of sign language. Diffusion tensor imaging (DTI) plays an important role in preoperative planning.Anatomical knowledge of the auditory tract is essential for lacrimal drainage surgeries, such as cochlear implantation.DTI-based biomarkers for brain changes and allows us to better understand the pathophysiological changes of auditory tract.Microstructural changes in the fiber tracts associated with the auditory pathway can distinguish sensorineural hearing loss (SNHL) from healthy subjects. Sensorineural hearing loss (SNHL) is the most common type and accounts for the majority of all hearing loss. SNHL is a congenital deficit and refers to any cause of hearing loss due to a pathology of the cochlea, auditory nerve, or central nervous system. One of the chief treatment planning is cochlear implant for these patients. So, it is necessary to evaluate the auditory system by imaging devices such as MRI (magnetic resonance imaging) before treatment. Diffusion tensor imaging tractography, or diffusion tensor imaging (DTI) tractography, is an MRI technique that measures the rate of water diffusion between cells to understand and create a map of the body's internal structures; it is most commonly used to provide imaging of the brain. The purpose of the present research was to assess the auditory system and its nerve routs in children before cochlear implant. This study showed that DT imaging is a novel approach for assessment of children with SNHL before and treatment.

Anesthetic modulation of water diffusion: Insights from a diffusion tensor imaging study.

Diffusion tensor imaging (DTI) in animal models are essential for translational neuroscience studies. A critical step in animal studies is the use of anesthetics. Understanding the influence of specific anesthesia regimes on DTI-derived parameters, such as fractional anisotropy (FA) and mean diffusivity (MD), is imperative when comparing results between animal studies using different anesthetics. Here, the quantification of FA and MD under different anesthetic regimes, alpha-chloralose and isoflurane, is discussed. We also used a range of b-values to determine whether the anesthetic effect was b-value dependent. The first group of rats (n=6) was anesthetized with alpha-chloralose (80mg/kg), whereas the second group of rats (n=7) was anesthetized with isoflurane (1.5%). DTI was performed with b-values of 500, 1500, and 1500s/mm2, and the MD and FA were assessed individually. Anesthesia-specific differences in MD were apparent, as manifested by the higher estimated MD under isoflurane anesthesia than that under alpha-chloralose anesthesia (P<0.001). MD values increased with decreasing b-value in all regions studied, and the degree of increase when rats were anesthetized with isoflurane was more pronounced than that associated with alpha-chloralose (P<0.05). FA quantitation was also influenced by anesthesia regimens to varying extents, depending on the brain regions and b-values. In conclusion, both scanning parameters and the anesthesia regimens significantly impacted the quantification of DTI indices.

Brain alterations in ovariohysterectomized rats revealed by diffusion tensor imaging.

Women undergoing hysterectomy with oophorectomy have an increased risk of Alzheimer's disease and Parkinson's disease. However, postoperative neuroimaging data on pathogenic processes in the brain are limited. The aim of this study was to investigate the potential effect of ovariohysterectomy on brain integrity in rat model using diffusion tensor imaging (DTI) technique for the first time. We enrolled 13 rats each in the control and ovariohysterectomy groups. Rats in the ovariohysterectomy group underwent the ovariohysterectomy at 7 weeks of age, and all rats underwent DTI scans at 9 weeks of age. The DTI-derived parameters, such as fractional anisotropy and mean diffusivity, were compared between the control and ovariohysterectomy groups. Compared to the control group, the ovariohysterectomy group showed significantly lower fractional anisotropy in various brain regions, including the corpus callosum, bilateral striatum, and bilateral cortex (all P < 0.05), suggesting neuronal injury in ovariohysterectomized rats. Mean diffusivity did not differ significantly between groups (all P > 0.05). Rats undergoing ovariohysterectomy had lower fractional anisotropy compared to control in widespread brain regions, suggesting neuronal injury and demyelination. Therefore, neuroimaging should be performed to monitor brain alterations in women after hysterectomy with bilateral oophorectomy in clinical settings.

Prognostication of overall survival in patients with brain metastases using diffusion tensor imaging and dynamic susceptibility contrast-enhanced MRI.

To investigate the prognostic utility of DTI and DSC-PWI perfusion-derived parameters in brain metastases patients. Retrospective analyses of DTI-derived parameters (MD, FA, CL, CP, and CS) and DSC-perfusion PWI-derived rCBVmax from 101 patients diagnosed with brain metastases prior to treatment were performed. Using semi-automated segmentation, DTI metrics and rCBVmax were quantified from enhancing areas of the dominant metastatic lesion. For each metric, patients were classified as short- and long-term survivors based on analysis of the best coefficient for each parameter and percentile to separate the groups. Kaplan-Meier analysis was used to compare mOS between these groups. Multivariate survival analysis was subsequently conducted. A correlative histopathologic analysis was performed in a subcohort (n = 10) with DTI metrics and rCBVmax on opposite ends of the spectrum. Significant differences in mOS were observed for MDmin (p < 0.05), FA (p < 0.01), CL (p < 0.05), and CP (p < 0.01) and trend toward significance for rCBVmax (p = 0.07) between the two risk groups, in the univariate analysis. On multivariate analysis, the best predictive survival model was comprised of MDmin (p = 0.05), rCBVmax (p < 0.05), RPA (p < 0.0001), and number of lesions (p = 0.07). On histopathology, metastatic tumors showed significant differences in the amount of stroma depending on the combination of DTI metrics and rCBVmax values. Patients with high stromal content demonstrated poorer mOS. Pretreatment DTI-derived parameters, notably MDmin and rCBVmax, are promising imaging markers for prognostication of OS in patients with brain metastases. Stromal cellularity may be a contributing factor to these differences. The correlation of DTI-derived metrics and perfusion MRI with patient outcomes has not been investigated in patients with treatment naïve brain metastasis. DTI and DSC-PWI can aid in therapeutic decision-making by providing additional clinical guidance.

Reproducibility of diffusion tensor imaging-derived parameters: implications for the streptozotocin-induced type 1 diabetic rats.

Diffusion tensor imaging (DTI) is a useful approach for studying neuronal integrity in animals. However, the test-retest reproducibility of DTI techniques in animals has not been discussed. Therefore, the first part of this work was to systematically elucidate the reliability of DTI-derived parameters in an animal study. Subsequently, we applied the DTI approach to an animal model of diabetes in a longitudinal manner. In Study 1, nine rats underwent two DTI sessions using the same scanner and protocols, with a gap of 4weeks. The reliability of the DTI-derived parameters was evaluated in terms of sessions and raters. In Study 2, nine rats received a single intraperitoneal injection of 70mg/kg streptozotocin (STZ) to develop diabetes. Longitudinal DTI scans were used to assess brain alterations before and 4weeks after STZ administration. In the test-retest evaluation, the inter-scan coefficient of variation (CoV) ranged from 3.04 to 3.73% and 2.12-2.59% for fractional anisotropy (FA) and mean diffusivity (MD), respectively, in different brain regions, suggesting excellent reproducibility. Moreover, rater-dependence had minimal effects on FA and MD quantification, with all inter-rater CoV values less than 4%. Following the onset of diabetes, FA in striatum and cortex were noted to be significantly lower relative to the period where they had not developed diabetes (both P < 0.05). However, when compared to the control group, a significant change in FA caused by diabetes was detected only in the striatum (P < 0.05), but not in the cortex. These results demonstrate good inter-rater and inter-scan reliability of DTI in animal studies, and the longitudinal setting has a beneficial effect on detecting small changes in the brain due to diseases.

The Impact of Ischemic Stroke on Gray and White Matter Injury Correlated With Motor and Cognitive Impairments in Permanent MCAO Rats: A Multimodal MRI-Based Study.

BackgroundIdentifying the alterations of the cerebral gray and white matter is an important prerequisite for developing potential pharmacological therapy for stroke. This study aimed to assess the changes of gray and white matter after permanent middle cerebral artery occlusion (pMCAO) in rats using magnetic resonance imaging (MRI), and to correlate them with the behavior performance.MethodsRats were subjected to pMCAO or sham surgery and reared for 30 days. Motor and cognitive function of the rats were examined by gait and Morris water maze (MWM) tests, respectively. Multimodal MRI was conducted to examine the functional and structural changes of the gray and white matter followed with luxol fast blue (LFB) staining.ResultsThe gait and MWM tests revealed significant motor and cognitive dysfunction in pMCAO rats, respectively. Magnetic resonance angiography presented abnormal intracranial arteries in pMCAO rats with reduced signal intensity of the anterior cerebral artery, anterior communicating cerebral artery, internal carotid artery, and increased basilar artery vessel signal compared with sham rats. Arterial spin labeling confirmed the decreased cerebral blood flow in the infarcted sensorimotor cortex and striatum. Structural T2-weighted imaging and T2 mapping showed brain atrophy and elevation of T2 value in the gray (sensorimotor cortex, striatum) and white (external capsule, internal capsule) matter of pMCAO rats. The results from diffusion tensor imaging (DTI) corresponded well with LFB staining showing reduced relative FA accompanied with increased relative AD and RD in the gray and white matter of pMCAO rats compared with sham rats. Fiber tracking derived from DTI further observed significantly reduced fiber density and length in the corresponding brain regions of pMCAO rats compared with sham rats. Specially, the DTI parameters (especially FA) in the relevant gray matter and white matter significantly correlated with the behavior performance in the gait and MWM tests.ConclusionCollectively, the gray and white matter damages could be non-invasively monitored in pMCAO rats by multimodal MRI. DTI-derived parameters, particularly the FA, might be a good imaging index to stage gray and white matter damages associated with post-stroke motor and cognitive impairments.

Widespread White Matter Microstructure Alterations Based on Diffusion Tensor Imaging and Diffusion Kurtosis Imaging in Patients With Pontine Infarction.

Neurological deficits after stroke are closely related to white matter microstructure damage. However, secondary changes in white matter microstructure after pontine infarction (PI) in the whole brain remain unclear. This study aimed to investigate the correlation of diffusion kurtosis imaging (DKI)-derived diffusion and kurtosis parameters of abnormal white matter tracts with behavioral function in patients with chronic PI. Overall, 60 patients with unilateral chronic PI (33 patients with left PI and 27 patients with right PI) and 30 normal subjects were recruited and underwent DKI scans. Diffusion parameters derived from diffusion tensor imaging (DTI) and DKI and kurtosis parameters derived from DKI were obtained. Between-group differences in multiple parameters were analyzed to assess the changes in abnormal white matter microstructure. Moreover, we also calculated the sensitivities of different diffusion and kurtosis parameters of DTI and DKI for identifying abnormal white matter tracts. Correlations between the DKI-derived parameters in secondary microstructure changes and behavioral scores in the PI were analyzed. Compared with the NC group, both left PI and right PI groups showed more extensive perilesional and remote white matter microstructure changes. The DKI-derived diffusion parameters showed higher sensitivities than did the DTI-derived parameters. Further, DKI-derived diffusion and kurtosis parameters in abnormal white matter regions were correlated with impaired motor and cognitive function in patients with PI. In conclusion, PI could lead to extensive white matter tracts impairment in perilesional and remote regions. Further, the diffusion and kurtosis parameters could be complementary for identifying comprehensive tissue microstructural damage after PI.

Bridging the Gap Between Morphometric Similarity Mapping and Gene Transcription in Alzheimer's Disease.

Disruptions in brain connectivity have been widely reported in Alzheimer’s disease (AD). Morphometric similarity (MS) mapping provides a new way of estimating structural connectivity by interregional correlation of T1WI- and DTI-derived parameters within individual brains. Here, we aimed to identify AD-related MS changing patterns and genes related to the changes and further explored the molecular and cellular mechanism underlying MS changes in AD. Both 3D-T1WI and DTI data of 106 AD patients and 106 well-matched healthy elderly individuals from the ADNI database were included in our study. Cortical regions with significantly decreased MS were found in the temporal and parietal cortex, increased MS was found in the frontal cortex and variant changes were found in the occipital cortex in AD patients. Mean MS in regions with significantly changed MS was positively or negatively associated with memory function. Negative MS-related genes were significantly downregulated in AD, specifically enriched in neurons, and participated in biological processes, with the most significant term being synaptic transmission. This study revealed AD-related cortical MS changes associated with memory function. Linking gene expression to cortical MS changes may provide a possible molecular and cellular substrate for MS abnormality and cognitive decline in AD.

DTI-derived parameters differ between moderate and severe traumatic brain injury and its association with psychiatric scores.

Diffusion tensor imaging (DTI) parameters in the corpus callosum have been suggested to be a biomarker for prognostic outcomes in individuals with diffuse axonal injury (DAI). However, differences between the DTI parameters on moderate and severe trauma in DAI over time are still unclear. A secondary goal was to study the association between the changes in the DTI parameters, anxiety, and depressive scores in DAI over time. Twenty subjects were recruited from a neurological outpatient clinic and evaluated at 2, 6, and 12months after the brain injury and compared to matched age and sex healthy controls regarding the DTI parameters in the corpus callosum. State-Trace Anxiety Inventory and Beck Depression Inventory were used to assess psychiatric outcomes in the TBI group over time. Differences were observed in the fractional anisotropy and mean diffusivity of the genu, body, and splenium of the corpus callosum between DAI and controls (p < 0.02). Differences in both parameters in the genu of the corpus callosum were also detected between patients with moderate and severe DAI (p < 0.05). There was an increase in the mean diffusivity values and the fractional anisotropy decrease in the DAI group over time (p < 0.02). There was no significant correlation between changes in the fractional anisotropy and mean diffusivity across the study and psychiatric outcomes in DAI. DTI parameters, specifically the mean diffusivity in the corpus callosum, may provide reliable characterization and quantification of differences determined by the brain injury severity. No correlation was observed with DAI parameters and the psychiatric outcome scores.

Effect of b Value on Imaging Quality for Diffusion Tensor Imaging of the Spinal Cord at Ultrahigh Field Strength.

Objective To explore the optimal b value setting for diffusion tensor imaging of rats' spinal cord at ultrahigh field strength (7 T). Methods Spinal cord diffusion tensor imaging data were collected from 14 rats (5 healthy, 9 spinal cord injured) with a series of b values (200, 300, 400, 500, 600, 700, 800, 900, and 1000 s/mm2) under the condition that other scanning parameters were consistent. The image quality (including image signal-to-noise ratio and image distortion degree) and data quality (i.e., the stability and consistency of the DTI-derived parameters, referred to as data stability and data consistency) were quantitatively evaluated. The min-max normalization method was used to process the calculation results of the four indicators. Finally, the image and data quality under each b value were synthesized to determine the optimal b value. Results b = 200 s/mm2 and b = 900 s/mm2 ranked in the top two of the comprehensive evaluation, with the best image quality at b = 200 s/mm2 and the best data quality at b = 900 s/mm2. Conclusion Considering the shortcomings of the ability of low b values to reflect the microstructure, b = 900 s/mm2 can be used as the optimal b value for 7 T spinal cord diffusion tensor scanning.

Role of bilateral corticobulbar tracts in dysphagia after middle cerebral artery stroke.

The corticobulbar tract is a potential neural pathway involved in swallowing. The frontal operculum, insular cortex, corona radiata and internal capsule, which are frequently involved in middle cerebral artery (MCA) strokes, are locations in which lesions cause dysphagia. However, it is unclear whether the locations are linked to the corticobulbar tract or whether corticobulbar tract integrity is associated with dysphagia severity. This study aimed to assess the association between corticobulbar tract integrity and dysphagia severity after MCA stroke. Thirty dysphagic patients after MCA stroke and 27 healthy controls were examined. Diffusion tensor imaging (DTI)-derived parameters of the corticobulbar tract were compared between patient and control groups. Next, patients were divided into mild and moderate-to-severe dysphagia groups, and DTI-derived parameters of the corticobulbar tract were compared between the subgroups. Logistic regression analysis was used to determine the association between corticobulbar tract integrity and dysphagia severity. The tract volume (TV) of the affected corticobulbar tract was lower in dysphagic patients than in healthy controls (P<0.001). According to dysphagia severity, TV of the unaffected corticobulbar tract was higher in the mild dysphagia group than in the moderate-to-severe dysphagia group (P=0.012). TV of the unaffected corticobulbar tract was independently associated with dysphagia severity according to the logistic regression model (adjusted odds ratio 0.817, 95% confidence interval 0.683-0.976). The corticobulbar tract was affected after MCA stroke and may be associated with dysphagia. A higher corticobulbar TV in the unaffected hemisphere was indicative of better swallowing function in dysphagic patients after MCA stroke.

Multiparametric MRI Evaluation of Liposomal Prostaglandins E1 Intervention on Hepatic Warm Ischemia-Reperfusion Injury in Rabbits.

Liposomal prostaglandin E1 (Lipo-PGE1) treatment should protect against hepatic warm ischemia-reperfusion injury (WIRI). Improved methods are needed for the noninvasive evaluation of hepatic responses to prophylactic Lipo-PGE1 pretreatment approaches. To demonstrate that multiparametric MRI measurements permit noninvasive differentiation of Lipo-PGE1 treatment outcomes in a hepatic WIRI animal model. Animal study. Seventy rabbits were randomly divided into a sham-operated group (A0), warm ischemia groups experiencing increasing periods of ischemia (A1-A3), and corresponding intervention groups (I1-I3) (n = 10 for each group). Imaging was performed at 3T using a multiecho gradient echo (GRE) sequence (repetition time / echo time [TR/TE], 75/2.57-24.25 msec) for R2* blood oxygenation level-dependent (BOLD) measurements, free-breathing single-shot echo-planar imaging (ss-EPI) sequence with two b-values (0 and 500 s/mm2 ) in 12 diffusion directions for diffusion tensor imaging (DTI), and a free-breathing ss-EPI sequence with eight b-values (0 to 800 s/mm2 ) for intravoxel incoherent motion (IVIM) measurements. The BOLD-derived parameter (R2*), DTI-derived parameters (ADC, FA), and IVIM-derived parameters (Dslow, Dfast, and PF) were calculated for comparisons between treatment groups and correlation to ALT, AST, and LDH levels. One-way analysis of variance (ANOVA), independent sample t-test, Spearman correlation, and receiver operating characteristic (ROC) analysis were performed. Histopathology confirmed the validity of the WIRI model and the efficacy of intervention with clear structure and morphology differences between the different ischemia times and between the Lipo-PGE1 treatment and control groups. Prolonged warm ischemia times resulted in higher R2* and FA values and gradually lower ADC, Dslow, Dfast, and PF values (all P < 0.05). The R2* and FA values were lower, and the ADC, Dslow, Dfast, and PF values were higher in the Lipo-PGE1 intervention groups compared with those in the warm ischemia group for each paired time. However, none of the parameters reached the levels of the A0 group (all P < 0.05). As the warm ischemia time increased, additional parameters demonstrated significant differences between warm ischemia time groups and corresponding intervention groups. At the shortest (30 min), middle (40 min), and longest (60 min) ischemia times, three, four, and five parameters were significantly different between the WIRI and intervention groups, respectively (all P < 0.05). ADC, Dslow, Dfast, and PF values were negatively correlated, while R2* and FA values were positively correlated with serum ALT (|r| = 0.312-0.606) and AST (|r| = 0.432-0.602) (all P < 0.05). ADC and Dfast values showed negative correlations, and R2* showed positive correlations with serum LDH (|r| = 0.323-0.542, all P < 0.05). ROC analysis showed that DTI yielded the strongest diagnostic performance for evaluating the improvement of WIRI. Multiparametric MRI can serve as a noninvasive radiologic evaluation for monitoring the protective impact of Lipo-PGE1 therapy on hepatic WIRI. 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;52:217-228.

Diffusion Tensor Model links to Neurite Orientation Dispersion and Density Imaging at high b-value in Cerebral Cortical Gray Matter

Diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) are widely used models to infer microstructural features in the brain from diffusion-weighted MRI. Several studies have recently applied both models to increase sensitivity to biological changes, however, it remains uncertain how these measures are associated. Here we show that cortical distributions of DTI and NODDI are associated depending on the choice of b-value, a factor reflecting strength of diffusion weighting gradient. We analyzed a combination of high, intermediate and low b-value data of multi-shell diffusion-weighted MRI (dMRI) in healthy 456 subjects of the Human Connectome Project using NODDI, DTI and a mathematical conversion from DTI to NODDI. Cortical distributions of DTI and DTI-derived NODDI metrics were remarkably associated with those in NODDI, particularly when applied highly diffusion-weighted data (b-value = 3000 sec/mm2). This was supported by simulation analysis, which revealed that DTI-derived parameters with lower b-value datasets suffered from errors due to heterogeneity of cerebrospinal fluid fraction and partial volume. These findings suggest that high b-value DTI redundantly parallels with NODDI-based cortical neurite measures, but the conventional low b-value DTI is hard to reasonably characterize cortical microarchitecture.

In vivo evaluation of human patellar tendon microstructure and microcirculation with diffusion MRI.

Patellar tendon (PT) microstructure integrity and microcirculation status play a crucial role in the progression of tendinopathy and tendon repair. To assess the feasibility and robustness of stimulated-echo based diffusion-weighted MRI with readout-segmented echo-planar imaging (ste-RS-EPI) for noninvasive assessment of microstructure and microcirculation of human PT. Prospective. Fifteen healthy volunteers. PT diffusion tensor imaging (DTI) and intravoxel incoherent motion (IVIM) were acquired with an ste-RS-EPI protocol on a 3T MRI scanner. Subjects were positioned with their PT at the magic angle. DTI-derived parameters including axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD), and fractional anisotropy (FA) were estimated with b-values of 0 and 800 s/mm2 and 12 diffusion directions. IVIM-derived parameters, f p , D* × f p , V b , and D* × V b were assessed in the central-third and the outer-two thirds of the PT with b-values of 0, 20, 30, 60, 80, 120, 200, 400, and 600 s/mm2 in three orthogonal directions. Paired t-tests were used to evaluate differences in IVIM parameters between the central-third and outer-two thirds regions of the patellar tendon. Paired t-tests and within-subject coefficient of variation were used to assess the intra- and intersession reproducibility of PT DTI and IVIM parameters. DTI parameters for healthy PT were 1.54 ± 0.09 × 10-3 mm2 /s, 1.01 ± 0.05 × 10-3 mm2 /s, 1.18 ± 0.06 × 10-3 mm2 /s, and 0.30 ± 0.04 for AD, RD, MD, and FA, respectively. Significantly higher (P < 0.05) IVIM parameters f p and D* × f p were observed in the outer-two thirds (6.1% ± 2.4% and 95.2 ± 49.6, respectively) compared with the central-third (3.8% ± 2.3% and 48.6 ± 35.2, respectively) of the PT. Diffusion MRI of PT with an ste-RS-EPI protocol is clinically feasible. Both DTI- and IVIM-derived parameters of the PT demonstrated good test-retest reproducibility and interrater reliability. 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:780-790.

Combined machine learning and diffusion tensor imaging reveals altered anatomic fiber connectivity of the brain in primary open-angle glaucoma

Parameters derived from diffusion tensor imaging (DTI) have been found to be significantly altered in the optic tracts, optic nerves, and optic radiations in patients with primary open-angle glaucoma (POAG). In this study, DTI-derived parameters were further constructed into fiber connectivity, and we investigated anatomical fiber connectivity changes within and beyond the visual pathway in POAG patients. DTI and T1-weighted magnetic resonance images were acquired in 18 POAG patients and 26 healthy controls (HC). White matter tracts based on the Brodmann atlases (BA) were constructed using the deterministic fiber tracking method. The mean fractional anisotropy (FA), fiber number (FN), and mean fiber length (FL) were measured and then evaluated using two-sample t-tests between POAG and HC. The fiber connectivity between regions was taken as the features for classifying HC and POAG using a machine learning method known as naïve Bayesian classification. The mean FA decreased in connections between visual cortex BA17/BA18 and cortex BA23/BA25/BA35/BA36, while it increased in the connections between cortex BA3/BA7/BA9 and BA5/BA6/BA45/BA25 in POAG. Classification using fibers where a significant difference in FN had been identified produced better accuracy (ACC = 0.89) than using FA or FL (ACC = 0.77 and 0.75, respectively). The FN of individual fiber connections with higher accuracy and significant changes in POAG involved brain regions associated with vision (BA19), depression (BA10/BA46/BA25), and memory (BA29). These findings strengthen the hypothesis that POAG involves changes in anatomical connectivity within and beyond the visual pathway. Classification using the machine learning method reveals that mean FN has the potential to be used as a biomarker for detecting white matter microstructure changes in POAG.

Laterality of cerebellar afferent and efferent pathways in a healthy right-handed population: A diffusion tensor imaging study.

The cerebellum communicates with the cerebral cortex through the cortico-ponto-cerebellar tract (CPCT, cerebellar afferent) and the dentato-rubro-thalamo-cortical tract (DRTCT, cerebellar efferent). This study explored the laterality of CPCT and DRTCT in a right-handed population. Forty healthy right-handed subjects (18 males and 22 females with age range of 26-79years old) who underwent diffusion tensor imaging (DTI) were retrospectively enrolled. Bilateral CPCT, DRTCT, and the corticospinal tract (CST) were reconstructed using probabilistic diffusion tensor tractography (DTT). Tract volume (TV) and fractional anisotropy (FA) were compared between dominant and non-dominant tracts. Subjects were divided into age groups (20-40, 41-60, and 61-80years), and the DTI-derived parameters of the groups were compared to determine age-related differences. TV and FA of non-dominant CPCT were higher than those of dominant CPCT, and the dominant CST was higher than the non-dominant CST. The TV and FA of DRTCT showed no side-to-side difference. The 61-80years age group had the highest TV of the dominant and non-dominant DRTCT among the three groups and the highest FA of the non-dominant CPCT and DRTCT. The results revealed the structural characteristics of CPCT and DRTCT using probabilistic DTT. Normal asymmetric patterns and age-related changes in cerebellar white matter tracts may be important to researchers investigating cerebro-cerebellar structural connectivity.

Pretreatment texture analysis of routine MR images and shape analysis of the diffusion tensor for prediction of volumetric response after radiosurgery for meningioma.

OBJECTIVEThe goal of this study was to identify parameters from routine T1- and T2-weighted MR sequences and diffusion tensor imaging (DTI) that best predict the volumetric changes in a meningioma after treatment with Gamma Knife radiosurgery (GKRS).METHODSIn 32 patients with meningioma, routine MRI and DTI data were measured before GKRS. A total of 78 parameters derived from first-level texture analysis of the pretreatment MR images, including calculation of the mean, SD, 2.5th and 97.5th percentiles, and kurtosis and skewness of data in histograms on a voxel-wise basis, were correlated with lesion volume change after a mean follow-up period of 3 years (range 19.5-63.3 months).RESULTSSeveral DTI-derived parameters correlated significantly with a meningioma volume change. The parameter that best predicted the results of GKRS was the 2.5th percentile value of the smallest eigenvalue (L3) of the diffusion tensor (correlation coefficient 0.739, p ≤ 0.001), whereas among the non-DTI parameters, only the SD of T2-weighted images correlated significantly with a tumor volume change (correlation coefficient 0.505, p ≤ 0.05, after correction for family-wise errors using false-detection-rate correction).CONCLUSIONSDTI-derived data had a higher correlation to shrinkage of meningioma volume after GKRS than data from T1- and T2-weighted image sequences. However, if only routine MR images are available, the SD of T2-weighted images can be used to predict control or possible progression of a meningioma after GKRS.

Pretreatment Texture Analysis of Routine Magnetic Resonance Images and Shape Analysis of the Diffusion Tensor Predict Volumetric Response after Radiosurgery for Meningiomas

Tumor progression after stereotactic radiosurgery remains a major complication in WHO grade I meningiomas, with figures reported between 5-10%. According to our previous study, Diffusion Tensor Imaging (DTI) parameters can differentiate between meningioma subtypes and predict the reduction in volume of meningiomas after SRS. However DTI is still not frequently performed for SRS. The objective of this study was to identify those parameters from routine T1- and T2-weigted Magnetic Resonance (MR) sequences, and as well as from DTI, which predict best volume changes of meningiomas after Gamma Knife Radio-Surgery (GKRS) treatment. In 32 patients (mean age 58y) with meningiomas (mean volume 8.80cm3, mean dose 14.2Gy), routine 3 Tesla MR images as well as 11 different DTI parameter maps, including skewness of tensor shape, were measured before SRS. A total of 104 parameters derived from first level texture analysis of the pre-treatment MR images, including calculation of mean, standard deviation, 2.5 and 97.5 percentiles, kurtosis and skewness of data histograms on a voxel-wise basis, were correlated with lesion volume change after a mean follow up period of 3 years (19.5 – 63.3 months). Mean volume change rate per month after SRS was 0.92%. 1 (3%) meningioma progressed, 5 (16%) meningiomas stayed stable and 26 (81%) regressed. Several DTI-derived parameters correlated significantly with meningioma volume change. The parameter to predict best response of SRS was the 2.5 percentile value of the planar spherical index of the diffusion tensor (correlation coefficient -0.682, p≤0.001), whereas from the non-DTI parameters, only standard deviation of T2-weighted data correlated significantly with tumor volume change (correlation coefficient 0.505, p≤0.05). Other factors, like original tumor size, prescription dose and patient’s age, did not present significant correlation. WHO grade I Meningiomas differ in tissue homogeneity and in radiosensitivity. DTI-derived parameters show a higher correlation to shrinkage of meningioma volume after SRS than data from T1- and T2-weigted sequences. Combinations of standard deviation of T2 and DTI parameters can further improve correlation. If only routine MR images are available, standard deviation of T2-weighted images may be considered to predict volumetric response of meningiomas after SRS.

Effects of Xiaoshuan Enteric-Coated Capsule on White and Gray Matter Injury Evaluated by Diffusion Tensor Imaging in Ischemic Stroke

Xiaoshuan enteric-coated capsule (XSECC) is a drug approved by the Chinese State Food and Drug Administration for the treatment of stroke. This study was to investigate the effects of XSECC on white and gray matter injury in a rat model of ischemic stroke by diffusion tensor imaging (DTI) and histopathological analyses. The ischemia was induced by middle cerebral artery occlusion (MCAO). The cerebral blood flow measured by arterial spin labeling was improved by treatment with XSECC on the 3rd, 7th, 14th and 30th days after MCAO. Spatiotemporal white and gray matter changes in MCAO rats were examined with DTI-derived parameters (fractional anisotropy, FA; apparent diffusion coefficient, ADC; axial diffusivity, λ//; radial diffusivity, λ⊥). The increased FA was found in the XSECC treatment group in the corpus callosum, external capsule and internal capsule, linked with the decreased λ//, λ⊥ and ADC on the 3rd day and reduced ADC on the 30th day in the external capsule, suggesting XSECC reduced the axon and myelin damage in white matter after stroke. The relative FA in the striatum, cortex and thalamus in XSECC treatment group was significantly increased on the 3rd, 7th, 14th and 30th days accompanied by the increased λ// on the 3rd day and reduced relative ADC and λ⊥ on the 30th day, indicating that XSECC attenuated cell swelling and membrane damage in the early stage and tissue liquefaction necrosis in the late stage in gray matter after stroke. Additionally, XSECC-treated rats exhibited increased mean fiber length assessed by diffusion tensor tractography. Moreover, histopathological analyses provided evidence that XSECC relieved nerve cell and myelin damage in white and gray matter after stroke. Our research reveals that XSECC could alleviate white and gray matter injury, especially reducing nerve cell damage and promoting the repair of axon and myelin after ischemic stroke.