Isotropic resolution diffusion tensor imaging of lumbosacral and sciatic nerves using a phase-corrected diffusion-prepared 3D turbo spin echo.

In this work, we aim to assess the significance of diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI) parameters in grading gliomas. Retrospective studies were performed on 53 subjects with gliomas belonging to WHO grade II (n=19), grade III (n=20) and grade IV (n=14). Expert marked regions of interest (ROIs) covering the tumour on T2-weighted images. Statistical texture measures such as entropy and busyness calculated over ROIs on diffusion parametric maps were used to assess the tumour heterogeneity. Additionally, we propose a volume heterogeneity index derived from cross correlation (CC) analysis as a tool for grading gliomas. The texture measures were compared between grades by performing the Mann-Whitney test followed by receiver operating characteristic (ROC) analysis for evaluating diagnostic accuracy. Entropy, busyness and volume heterogeneity index for all diffusion parameters except fractional anisotropy and anisotropy of kurtosis showed significant differences between grades. The Mann-Whitney test on mean diffusivity (MD), among DTI parameters, resulted in the highest discriminability with values of P=0.029 (0.0421) for grade II vs. III and P=0.0312 (0.0415) for III vs. IV for entropy (busyness). In DKI, mean kurtosis (MK) showed the highest discriminability, P=0.018 (0.038) for grade II vs. III and P=0.022 (0.04) for III vs. IV for entropy (busyness). Results of CC analysis illustrate the existence of homogeneity in volume (uniformity across slices) for lower grades, as compared to higher grades. Hypothesis testing performed on volume heterogeneity index showed P values of 0.0002 (0.0001) and 0.0003 (0.0003) between grades II vs. III and III vs. IV, respectively, for MD (MK). In summary, the studies demonstrated great potential towards automating grading gliomas by employing tumour heterogeneity measures on DTI and DKI parameters.

Comparison of Turbo Spin Echo and Echo Planar Imaging for intravoxel incoherent motion and diffusion tensor imaging of the kidney at 3 Tesla

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.

The aim of this study was to determine the accuracy and reliability of shoulder magnetic resonance (MR) arthrography with three-dimensional (3D) isotropic intermediate-weighted turbo spin-echo (TSE) sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) in the diagnosis of superior labrum anterior-to-posterior (SLAP) lesions compared with two-dimensional (2D) TSE at 3.0 T. MR arthrograms, including 2D TSE and 3D TSE-SPACE, in 87 patients who underwent arthroscopy were retrospectively analysed by two reviewers for the presence and type of SLAP lesions. Sensitivity and specificity were compared using McNemar's test, and inter-observer agreement was calculated using Cohen's kappa. Receiver operating characteristic (ROC) curve analyses were performed. The mean sensitivity, specificity and accuracy were 90%, 85% and 86% for 2D TSE, and 81%, 86% and 85% for 3D TSE-SPACE respectively, with no statistically significant differences. Inter-observer agreements were substantial in 2D TSE (κ = 0.76) and 3D TSE-SPACE (κ = 0.68). The areas under the ROC curves were 0.92 for 2D TSE and 0.90 for 3D TSE-SPACE, which were not significantly different. MR arthrography with 3D TSE-SPACE showed comparable accuracy and substantial inter-observer agreement for the diagnosis of SLAP lesions.

This study investigated correlations between American Spinal Injury Association (ASIA) clinical injury motor scores in patients with traumatic cervical cord injury and magnetic resonance (MR) diffusion tensor imaging (DTI) parameters. Conventional imaging and DTI were performed to evaluate 25 patients (age, 39.7±13.9 years; 4 women, 21 men) with blunt spinal cord injury and 11 volunteers (age, 31.5±10.7 years; 3 women, 8 men). Cord contusions were hemorrhagic (HC) in 13 and non-hemorrhagic (NHC) in 12 patients. The spinal cord was divided into three regions to account for spatial and pathological variation in DTI parameters. Comparisons of regional and injury site mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity ( λ(⊥)), and longitudinal diffusivity ( λ(‖)) were made with control subjects. ASIA motor scores were correlated with DTI using linear regression analysis. HC and NHC patients showed significant reduction (p<0.001) in MD and λ(‖) in all three regions. At the injury site, significant decreases in FA and λ(‖) were seen for both injury groups (p<0.001). λ(⊥) values were significantly increased only for patients with NHC (p<0.05). Significant reduction in FA and λ(‖) (p<0.0001) was observed at the whole cord level between the injured (NH and NHC) and control groups. Within the NHC group, strong correlations were observed between ASIA motor scores and average MD, FA, λ(⊥), and λ(‖) at the injury site. However, no correlation was observed within the HC group between any of the DTI parameters and ASIA motor scores. DTI parameters reflect the severity of spinal cord injury and correlate well with ASIA motor scores in patients with NHC.

The aim is to investigate whether there is a microstructural change in the white matter pathways in patients with spontaneous intracranial hypotension (SIH). Additionally, the relationship between conventional magnetic resonance imaging (MRI) findings and diffusion tensor imaging (DTI) parameters is determined. Thirty patients diagnosed with SIH and 31 control patients (between January 2019 and February 2024) were included in the case-control study. MRI findings constituting the Bern score were evaluated in contrast-enhanced brain MRI. Ten different white matter pathways were evaluated with the following DTI parameters: fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusion (AD), and radial diffusion (RD). We also examined the association between MRI findings and DTI parameters. In the cingulum, a decreased FA value (Z = -3.18, p = 0.002) was observed in patients with SIH, indicating disruption of white matter integrity and weakened synaptic transmission in this region. In the corona radiata, significant reductions were observed in both FA (Z = -5.67, p < 0.001) and AD (Z = -3.59, p < 0.001), alongside an increase in RD (Z = -4.99, p < 0.001). The concomitant increase in RD further supports the idea of potential damage to the myelin sheath, which, together with other findings, may reflect disruptions in white matter architecture that underlie the cognitive and motor deficits frequently seen in patients with SIH. In the splenium of the corpus callosum, a significant reduction in AD (Z = -3.00, p = 0.007) was also noted. In the anterior limb of the internal capsule (ALIC), both FA (Z = -4.57, p < 0.001) and AD (Z = -2.73, p = 0.012) values decreased, while RD increased (Z = -2.93, p = 0.007). These alterations suggest the involvement of motor and sensory pathways. In the posterior limb of the internal capsule (PLIC), significant reductions were found in both FA (Z = -5.59, p < 0.001) and AD (Z = -3.82, p < 0.001), along with an increase in RD (Z = -5.49, p < 0.001). In the corticospinal tract, patients with SIH exhibited a decrease in FA (Z = -4.15, p < 0.001), an increase in ADC (Z = -2.87, p = 0.008), and an increase in RD (Z = -3.73, p < 0.001). These findings represent significant microstructural changes reflecting a reduction in the integrity of motor pathways in white matter. In the middle cerebellar peduncle (MCP), patients with SIH showed increased ADC (Z = -4.78, p < 0.001) and RD (Z = -3.23, p = 0.002). Similarly, in optic radiation, there was decreased FA (Z = -4.55, p < 0.001) and AD (Z = -2.59, p = 0.018), with increased RD (Z = -2.95, p = 0.007). In the correlation analysis, positive correlations were found between suprasellar distance and AD values in both the ALIC (rs = 0.451, p = 0.012) and MCP (rs = 0.416, p = 0.022). These findings suggest that structural changes and anatomical shifts, especially in the suprasellar region, may be associated with microstructural changes in the adjacent white matter pathways. We revealed microstructural changes in white matter in SIH. The alterations in DTI parameters may suggest that the white matter microarchitecture is changed as a result of mechanical compression of the axons in the white matter pathways due to brain prolapse and venous congestion.

BackgroundWe sought to compare diffusion tensor imaging (DTI) parameters in vivo and ex vivo in the brain and to explore the effects of radiofrequency coil and number of excitations on ex vivo DTI parameters.MethodsSix Sprague–Dawley rat brains were used to obtain in vivo and ex vivo DTI maps with different coils and number of excitations. DTI parameters of white matter and grey matter including diffusivities, fractional anisotropy, and other dimensionless ratios (λ2/λ1, λ3/λ1, and λ2/λ3) were obtained from reconstruction maps. Comparisons of ex vivo signal-to-noise ratio with different coils and number of excitations were conducted.ResultsDiffusivities decreased significantly after fixation in all the selected white matter and grey matter regions of interest (all at p < 0.001). The diffusivities in white matter integrity decreased more than in grey matter integrity after fixation (all at p < 0.001). The ratio of λ2/λ3 in the major brain structures changed after fixation (most at p < 0.05). There were differences in major ex vivo brain structures in DTI parameters and signal-to-noise ratio between surface coil and volume coil, and between one and four excitations (most at p < 0.05).ConclusionThe impact of fixation, coil, and number of excitations on DTI parameters should be taken into consideration in clinical and experimental studies at 7.0 T.

Objective To explore the correlations relating functional MRI (fMRI) and diffusion tensor imaging (DTI) parameters with pre-operative neurological status and post-operative outcomes for patients with cervical spondylotic myelopathy (CSM). Methods Eighty-seven CSM patients treated with surgical decompression and 38 healthy counterparts were enrolled as the CSM and control groups respectively. DTI and fMRI of the cervical spine were performed while the subjects performed a finger-tapping task with their right hands before the operation and 6 months later. The control group was evaluated only when they were enrolled. All of the patients were given systematic rehabilitation treatment after the surgery. The Japanese Orthopaedic Association (JOA) scoring system for CSM was used to evaluate neurological status, and a JOA recovery rate <50% was defined as a poor recovery. Results Compared with the healthy controls, the pre-operative patients showed significantly higher volume of activation (VOA) in the left precentral gyrus (PrCG), but that had decreased significantly 6 months after the surgery. Before the surgery, the patients′ fractional isotropy (FA) was significantly less than that of the controls, but it had increased significantly 6 months after the operation. There was no difference in VOA in the left postcentral gyrus (PoCG) between the CSM patients and the controls before the surgery. The VOA ratio (PrCG/PoCG), VOA-PrCG, VOA-PoCG and FA were significantly correlated with both the JOA scores and recovery rates. Receiver operating characteristic (ROC) curve analyses were performed for the predictive ability with respect to surgical outcomes. The largest area under the ROC curve was observed for the VOA ratio (0.805), followed by FA (0.740), and the VOA-PrCG (0.715). The fMRI and DTI showed better potential for predicting functional outcomes than with standard MRI parameters. Multivariate logistic regression revealed that the VOA ratio and FA were independently associated with poor outcomes. Conclusions fMRI and DTI parameters may be more valuable than conventional MRI results for neurological assessment and prognosis with CSM patients. They can also provide references for making up rehabilitation plans. Key words: Cervical spondylotic myelopathy; Functional magnetic resonance imaging; Cortical reorganization; Diffusion tensor imaging

Assessment of peripheral neuropathy in type 2 diabetes by diffusion tensor imaging: A case-control study

Multi-slice 2D turbo spin echo (TSE) sequences are widely used for T2-weighted MR imaging of the liver. On the other hand, there is a demand for 3D imaging to enable the observation of thinner slices, though 3D TSE has often been associated with a high SAR (specific absorption rate) which is caused by repeated 180-degree refocusing pulses. The high SAR has been a limiting factor for 3D TSE, especially with 3.0 Tesla scanners. We carried out free-breath 3D SPACE T2-weighted MR imaging of the liver to yield TSE contrast. This is a variant of 3D TSE that employs specially-designed refocusing pulses to reduce the SAR. The PACE (prospective acquisition correction) technique was used to eliminate motion artifacts that appear conspicuously at 3 Tesla as compared with 1.5 Tesla. The 3D SPACE parameters were as follows; FOV=384mm and base matrix size=320, effective slice thickness=1.2mm. Five volunteers were examined with this sequence on a 3.0-Tesla whole-body scanner. The acquired isotropic 3D image data set was processed with both multi-planar reconstruction (MPR) and volume rendering technique (VRT) to yield images with high quality and very distinct continuity. Such processing was possible due to the isotropic 1.2-mm resolution made feasible by the 3D SPACE sequence. 3D T2-weighted imaging of the liver was performed successfully and safely by combining 3D SPACE and PACE, and the high-resolution isotropic image data assured the continuity of blood vessels and the cystic duct of the liver. I.

PurposeEcho planar imaging is an attractive rapid imaging readout that can image hyperpolarized compounds in vivo. By alternating the sign of the phase encoding gradient waveform, spatial offsets arising from uncertain frequency shifts can be determined. We show here that blip‐reversed echo planar imaging can also be used to correct for susceptibility and B0 inhomogeneity effects that would otherwise produce image‐domain distortion in the heart.MethodsPreviously acquired blip‐reversed cardiac 3D‐Spectral‐Spatial echo planar imaging volumetric timecourses of hyperpolarized [1‐13C]pyruvate were distortion corrected by a deformation field estimated by reconstructing signal‐to‐noise ratio (SNR)‐weighted progressively subsampled temporally summed images of each metabolite.ResultsReconstructing blip‐reversed data as proposed produced volumetric timecourses that overlaid with proton reference images more consistently than without such corrections.ConclusionThe method proposed may form an attractive method to correct for image‐domain distortions in hyperpolarized echo planar imaging experiments. Magn Reson Med 79:2135–2141, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Diffusion tensor imaging (DTI) is a noninvasive, quantitative MRI technique that measures white matter (WM) integrity. Many brain dimensions are heritable, including white matter integrity measured with DTI. Family studies are valuable to provide insights into the interactive effects of non-environmental factors on multiple sclerosis (MS). To examine the contribution of familial factors to the diffusion signals across WM microstructure, we performed DTI and calculated neurite orientation dispersion plus density imaging (NODDI) diffusion parameters in two patient groups comprising familial and sporadic forms of multiple sclerosis and their unaffected relatives. We divided 111 subjects (49 men and 62 women: age range 19–60) into three groups conforming to their MS history. The familial MS group included 30 participants (patients; n = 16, healthy relatives; n = 14). The sporadic group included 41 participants (patients; n = 10, healthy relatives; n = 31). Forty age-matched subjects with no history of MS in their families were defined as the control group. To study white matter integrity, two methods were employed: one for calculating the mean of DTI, FA, and MD parameters on 18 tracts using Tracts Constrained by Underlying Anatomy (TRACULA) and the other for whole brain voxel-based analysis using tract-based spatial statistics (TBSS) on NDI and ODI parameters derived from NODDI and DTI parameters. Voxel-based analysis showed considerable changes in FA, MD, NDI, and ODI in the familial group when compared with the control group, reflecting widespread impairment of white matter in this group. The analysis of 18 tracts with TRACULA revealed increased MD and FA reduction in more tracts (left and right ILF, UNC, and SLFT, forceps major and minor) in familial MS patients vs. the control group. There were no significant differences between the patient groups. We found no consequential changes in healthy relatives of both patient groups in voxel-based and tract analyses. Considering the multifactorial etiology of MS, familial studies are of great importance to clarify the effects of certain predisposing factors on demyelinating brain pathology.

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The aim of this study was to determine whether quantitative diffusion tensor imaging (DTI) adds diagnostic accuracy in magnetic resonance neurography. This prospective study was approved by the institutional review board. We enrolled 16 patients with peripheral polyneuropathy of various etiologies involving the upper arm and 30 healthy controls. Magnetic resonance neurography was performed at 3 T using transverse T2-weighted (T2-w) turbo spin echo and spin echo planar imaging diffusion-weighted sequences. T2-weighted normalized signal (nT2), fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity (RD), and axial diffusivity (AD) of the median, ulnar, and radial nerves were quantified after manual segmentation. Diagnostic performance of each separate parameter and combinations of parameters was assessed using the area under the receiver operating characteristic curve (AUC). Bootstrap validation was used to adjust for potential overfitting. Average nT2, ADC, RD, and AD values of the median, ulnar, and radial nerve were significantly increased in neuropathy patients compared with that in healthy controls (nT2, 1.49 ± 0.05 vs 1.05 ± 0.05; ADC, 1.4 × 10(-3) ± 2.8 × 10(-5) mm(2)/s vs 1.1 × 10(-3) ± 1.3 × 10(-5) mm(2)/s; RD, 9.5 × 10(-4) ± 2.9 × 10(-5) mm(2)/s vs 7.2 × 10(-4) ± 1.3 × 10(-5) mm(2)/s; AD, 2.3 × 10(-3) ± 3.7 × 10(-5) mm(2)/s vs 2.0 × 10(-3) ± 2.2 × 10(-5) mm(2)/s; P < 0.001 for all comparisons). Fractional anisotropy values were significantly decreased in patients (0.51 ± 0.01 vs 0.59 ± 0.01; P < 0.001). T2-weighted normalized signal and DTI parameters had comparable diagnostic accuracy (adjusted AUC: T2-w, 0.92; FA, 0.88; ADC, 0.89; AD, 0.84; RD, 0.86). Combining DTI parameters significantly improved the diagnostic accuracy over single-parameter analysis. In addition, the combination of nT2 with DTI parameters yielded excellent adjusted AUCs up to 0.97 (nT2 + FA). Diffusion tensor imaging has high diagnostic accuracy in peripheral neuropathy. Combining DTI with T2 can outperform T2-w imaging alone and provides added value in magnetic resonance neurography.

The aim of this study was to describe the development of morphologic and diffusion tensor imaging sequences of peripheral nerves at 7 T, using carpal tunnel syndrome (CTS) as a model system of focal nerve injury. Morphologic images were acquired at 7 T using a balanced steady-state free precession sequence. Diffusion tensor imaging was performed using single-shot echo-planar imaging and readout-segmented echo-planar imaging sequences. Different acquisition and postprocessing methods were compared to describe the optimal analysis pipeline. Magnetic resonance imaging parameters including cross-sectional areas, signal intensity, fractional anisotropy (FA), as well as mean, axial, and radial diffusivity were compared between patients with CTS (n = 8) and healthy controls (n = 6) using analyses of covariance corrected for age (significance set at P < 0.05). Pearson correlations with Bonferroni correction were used to determine association of magnetic resonance imaging parameters with clinical measures (significance set at P < 0.01). The 7 T acquisitions with high in-plane resolution (0.2 × 0.2mm) afforded detailed morphologic resolution of peripheral nerve fascicles. For diffusion tensor imaging, single-shot echo-planar imaging was more efficient than readout-segmented echo-planar imaging in terms of signal-to-noise ratio per unit scan time. Distortion artifacts were pronounced, but could be corrected during postprocessing. Registration of FA maps to the morphologic images was successful. The developed imaging and analysis pipeline identified lower median nerve FA (pisiform bone, 0.37 [SD 0.10]) and higher radial diffusivity (1.08 [0.20]) in patients with CTS compared with healthy controls (0.53 [0.06] and 0.78 [0.11], respectively, P < 0.047). Fractional anisotropy and radial diffusivity strongly correlated with patients' symptoms (r = -0.866 and 0.866, respectively, P = 0.005). Our data demonstrate the feasibility of morphologic and diffusion peripheral nerve imaging at 7 T. Fractional anisotropy and radial diffusivity were found to be correlates of symptom severity.