Recovery Sequences Research Articles

Deep medullary vein abnormalities impact white matter hyperintensity volume through increases in interstitial free water

BackgroundOur intent was to explore the mediating role of interstitial free water (FW) linking deep medullary vein (DMV) score to white matter hyperintensity (WMH) volume.MethodsOur research team conducted a forward-looking analysis of initial clinical and imaging information gathered from 125 patients with cerebral small vessel disease. We identified six anatomic DMV regions on susceptibility weighted imaging (SWI) studies. Each region earned a score of 0–3, determined by the visual conditions of vessels, summing all six to generate a DMV score. We utilized fluid-attenuated inversion recovery (FLAIR) sequences to measure the volume of WMH. Additionally, we employed diffusion tensor imaging (DTI) to assess FW value.ResultsDMV score significantly positively correlated with FW value and with WMH volume (p < 0.05), and value of FW positively correlated with WMH volume (p < 0.05). The indirect effect of DMV score on WMH volume was mediated by FW (β = 0.281, 95% confidence interval [CI]: 0.178–0.388), whether adjusted for age and gender (β = 0.142, 95% CI: 0.058–0.240) or for age, gender and vascular risk factors (β = 0.141, 95% CI: 0.054–0.249).ConclusionDMV score correlate with WMH volume by virtue of FW increases in white matter.

Free-breathing 3D cardiac extracellular volume (ECV) mapping using a linear tangent space alignment (LTSA) model.

To develop a new method for free-breathing 3D extracellular volume (ECV) mapping of the whole heart at 3 T. A free-breathing 3D cardiac ECV mapping method was developed at 3 T. T1 mapping was performed before and after contrast agent injection using a free-breathing electrocardiogram-gated inversion recovery sequence with spoiled gradient echo readout. A linear tangent space alignment model-based method was used to reconstruct high-frame-rate dynamic images from (k,t)-space data sparsely sampled along a random stack-of-stars trajectory. Joint T1 and transmit B1 estimation were performed voxel-by-voxel for pre- and post-contrast T1 mapping. To account for the time-varying T1 after contrast agent injection, a linearly time-varying T1 model was introduced for post-contrast T1 mapping. ECV maps were generated by aligning pre- and post-contrast T1 maps through affine transformation. The feasibility of the proposed method was demonstrated using in vivo studies with six healthy volunteers at 3 T. We obtained 3D ECV maps at a spatial resolution of 1.9 × 1.9 × 4.5 mm3 and a FOV of 308 × 308 × 144 mm3, with a scan time of 10.1 ± 1.4 and 10.6 ± 1.6 min before and after contrast agent injection, respectively. The ECV maps and the pre- and post-contrast T1 maps obtained by the proposed method were in good agreement with the 2D MOLLI method both qualitatively and quantitatively. The proposed method allows for free-breathing 3D ECV mapping of the whole heart within a practically feasible imaging time. The estimated ECV values from the proposed method were comparable to those from the existing method.

Parasagittal dural volume correlates with cerebrospinal fluid volume and developmental delay in children with autism spectrum disorder

BackgroundThe parasagittal dura, a tissue that lines the walls of the superior sagittal sinus, acts as an active site for immune-surveillance, promotes the reabsorption of cerebrospinal fluid, and facilitates the removal of metabolic waste products from the brain. Cerebrospinal fluid is important for the distribution of growth factors that signal immature neurons to proliferate and migrate. Autism spectrum disorder is characterized by altered cerebrospinal fluid dynamics.MethodsIn this retrospective study, we investigated potential correlations between parasagittal dura volume, brain structure volumes, and clinical severity scales in young children with autism spectrum disorder. We employed a semi-supervised two step pipeline to extract parasagittal dura volume from 3D-T2 Fluid Attenuated Inversion Recovery sequences, based on U-Net followed by manual refinement of the extracted parasagittal dura masks.ResultsHere we show that the parasagittal dura volume does not change with age but is significantly correlated with cerebrospinal fluid (p-value = 0.002), extra-axial cerebrospinal fluid volume (p-value = 0.0003) and severity of developmental delay (p-value = 0.024).ConclusionsThese findings suggest that autism spectrum disorder children with severe developmental delay may have a maldeveloped parasagittal dura that potentially perturbs cerebrospinal fluid dynamics.

Early detection of myocardial iron overload in patients with β-thalassemia major using cardiac magnetic resonance T1 mapping

BackgroundThe T2* technique, used for quantifying myocardial iron content (MIC), has limitations in detecting early myocardial iron overload (MIO). The in vivo mapping of the myocardial T1 relaxation time is a promising alternative for the early detection and management of MIO. Methods32 β-thalassemia major (βTM) patients aged 11.5 ± 4 years and 32 healthy controls were recruited and underwent thorough clinical and laboratory assessments. The mid-level septal iron overload was measured through T1 mapping using a modified Look-Locker inversion recovery sequence with a 3 (3 s) 3 (3 s) 5 scheme. Septum was divided at the mentioned level into 3 zones corresponding to segments 8 and 9 in the cardiac segmentation model. Results21.9 % of βTM had clinical cardiac morbidity. The cut-off of T1 mapping of hepatic and myocardium to differentiate between the patients and control groups was ≤466 and ≥ 923 ms respectively. The T1 technique was able to detect 4 patients with high MIC, two of them were not detected by the T2* technique. There was a statistically significant correlation between the average T1 values of the studied zones in patients with βTM and the liver iron content (LIC), the T1 values within segment 8 of the liver, age of patients, the age at first transfusion, age of splenectomy and serum ferritin value. ConclusionThe addition of the T1 mapping sequence to the conventional T2* technique was able to increase the efficacy of the MIC detection protocol by earlier detection of MIO. This would guide chelation therapy to decrease myocardial morbidity.

UTILITY OF CONTRAST-ENHANCED T2-FLAIR FOR IMAGING OF BRAIN METASTASESUSING A HALF-DOSE HIGH-RELAXIVITY CONTRAST AGENT IN COMPARISON WITH ROUTINE DOSE CONTRAST-ENHANCED BRAIN IMAGING

Aim &amp; Objectives: This study aims to assess the efficacy of delayed contrast-enhanced T2 fluid-attenuated inversion recovery (CE-T2 FLAIR) by using half dose high relaxivity contrast agent to assess the degree of enhancement among the lesions and to detect additional metastatic brain lesions usually smaller lesions(&lt;5mm), which are significantly missed on routine-dose CE-T1 weighted imaging (CE-T1WI). Material &amp; Methods:The main source of data for this study was radiologically diagnosed lung cancer patients who were clinically suspected to have brain metastasis referred from various departments of Silchar Medical College and Hospital. The studywas carried out for a period of 1 year from March 1, 2023, to February 29, 2024, A total of 40 patients with brain metastases were scanned using a SIEMENS TIM AVANTO 1.5T scanner, routine MR pulse sequences pre- and post-contrast administration were acquired. Results: Out of 40 patients, males were more affected (57.5 %) than females (42.5 %). The highest number of cases were found between the 61-70 years age group with the lung (31 cases) being the most common primary malignancy causing brain metastases. A total of 90 lesions were detected among 40 patients which were grouped into A (25 lesions), B (36 lesions), and C (29 lesions) groups. A total of 6 lesions were missed on Routine dose contrast-enhanced brain imaging of which 2 lesions belong to group B (Rim enhancing lesions &gt;5mm) and 4 lesions belong to group C (Lesions &lt;5mm), however, these lesions were picked up on delayed half dose contrast-enhanced FLAIR images. The contrast ratio (CR) on 3 consecutive half dose CE-T2 FLAIR ranged between 59.09%-76.80%, suggesting that delay in imaging post-contrast administration resulted in a significant increase in the contrast ratio (CR) among metastatic lesions. Conclusions: CE-T1-weighted sequences and CE-T2 FLAIR sequences complement each other effectively in evaluating brain metastases. Bigger and homogenously enhancing lesions are best seen on CE-T1-weighted sequences. Smaller lesions and lesions showing rim enhancement are best visualized on delayed (5 min) CE-T2 fluid-attenuated inversion recovery (FLAIR) sequences with half the dose ofcontrast agent (gadobenatedimeglumine) compared to routine dose CE-T1-weighted sequences. This approach serves as a cost-saving measure for both patients and the healthcare system.

Fluid-Attenuated Inversion Recovery Sequence in MRI in Distinguishing Fluid Cyst from Tumor in the Brain

Nuclear magnetic resonance (NMR) is a physical phenomenon used to investigate the characteristics of atomic nuclei. It is the absorption and emission of energy by nuclei in a magnetic field, which can offer extensive information on the structure, dynamics, reaction state, and chemical environment of molecules. Magnetic Resonance Imaging (MRI) is the safest imaging method. It gives a visual representation of human tissue without surgical intervention for clinical diagnosis. In this research, Fast Spin Echo (SE), Multi-Slice Spin Echo (MSSE), and Fluid Attenuated Inversion Recovery (FLAIR) sequences were used. The case under study is placed in an i-open permanent MRI system type in order to image a brain lesion. The obtained signals are encoded to fill k-space through the three stages, i.e., slice selection, phase encoding and frequency. The MRI-processed brain image is reconstructed by inverse Fourier transform in order to find the location of the cyst, and T1 weighted, T2 weighted, and FLAIR tests were performed to obtain three types of images. The images were compared with normal images in each type of applied sequence. Subsequently, the fluid signal was specifically attenuated in the targeted location to help distinguish between a tumor and fluid in the transverse relaxation time-weighted image. The signal was attenuated in the designated location, turned black, and appeared the color of free water, like cerebrospinal fluid, indicating that it was a fluid rather than a tumor. Consequently, a cyst fluid lesion is detected. Our study establishes a foundation for utilizing free fluid signal attenuation to differentiate between cyst fluid and tumors when other sequences fail to do the same.

Evaluation of Inflammatory Disease Activity in the Sacroiliac Joints Using Magnetic Resonance Imaging: A Comparative Analysis of Short-Tau Inversion Recovery, Post-Contrast, and Diffusion-Weighted Imaging –Preliminary Study

Introduction: It is essential to detect sacroiliitis earlier to decrease morbidity and unwanted complications such as ankylosing of sacroiliac joints. In recent studies, magnetic resonance imaging (MRI) serves as a key diagnostic tool for identifying sacroiliitis and is now included in the diagnostic criteria. We aim to detect the utility of diffusion-weighted imaging on the MRI in diagnosing sacroiliitis and measure ADC values for the response to treatment in future studies. Materials -methods: There were 39 patients (16 male, 20 female). A 1.5 Tesla MR device with a pelvic coil was used. The sequences were T1 (before and after intravenous contrast administration of gadolinium), T2-weighted fast field echo, short tau inversion recovery (STIR), diffusion-weighted (DW) images, and apparent diffusion coefficient (ADC) mapping. Sacroiliac joints were divided into four quadrants, and two radiologists interpreted all the sequences by giving scores from 0 to 3 depending on bone marrow edema from none to severe. The concordance of scores assigned to STIR, T1-weighted gadolinium-enhanced images, ADC mapping, and diffusion-weighted MR images was evaluated by calculating intraclass correlation coefficients. Results: A statistically significant positive correlation was observed between the activity scores derived from short tau inversion recovery (STIR) and other magnetic resonance (MR) sequences, namely T1-weighted gadolinium-enhanced images, apparent diffusion coefficient (ADC) mapping, and diffusion-weighted MR images. Conclusion: Active bone marrow abnormalities were identified with comparable efficacy using STIR imaging and other MR sequences (T1W-Gad, ADC mapping, DW-MR). In our study, we tried to emphasize the role of the diffusion-weighted images near the other sequences. Diffusion is a fast, easy-applied sequence. After increased experience in the diffusion-weighted images, routine application of this sequence will increase, and even becoming one of the diagnostic criteria will be inevitable. The difference in DWI from the other sequences is that it is measurable. The response to treatment may be followed up by ADC values.

Quantifying the reproducibility and longitudinal repeatability of radiomics features in magnetic resonance Image-Guide accelerator Imaging: A phantom study

ObjectiveThis study aimed to quantitatively evaluate the inter-platform reproducibility and longitudinal acquisition repeatability of MRI radiomics features in Fluid-Attenuated Inversion Recovery (FLAIR), T2-weighted (T2W), and T1-weighted (T1W) sequences on MR-Linac systems using an American College of Radiology (ACR) phantom. Materials and MethodsThis study used two MR-Linac systems (A and B) in different cancer centers. The ACR phantom was scanned on system A daily for 30 consecutive days to evaluate longitudinal repeatability. Additionally, retest data were collected after repositioning the phantom. Inter-platform reproducibility was assessed by conducting scans under identical conditions using system B. Regions of interest were delineated on the T1W sequence from system A and mapped to other sequences via rigid registration. Intra-observer and inter-observer comparisons were conducted. Repeatability and reproducibility were assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV). Robust radiomics features were identified based on ICC>0.9 and CV<10 %. ResultsAnalysis showed that a higher proportion of radiomics features derived from longitudinal FLAIR sequence (51.65 %) met robustness criteria compared to T2W (48.35 %) and T1W (43.96 %). Additionally, more inter-platform features from the FLAIR sequence (62.64 %) were robust compared to T2W (42.86 %) and T1W (39.56 %). Test-retest and intra-observer repeatability were excellent across all sequences, with a median ICC of 0.99 and CV<5%. However, inter-observer reproducibility was inferior, especially for the T1W sequence. ConclusionsDifferent sequences show variations in repeatability and reproducibility. The FLAIR sequence demonstrated advantages in both longitudinal repeatability and inter-platform reproducibility. Caution is warranted when interpreting data, particularly in longitudinal or multiplatform radiomics studies.

Utilizing Radiomics of Peri-Lesional Edema in T2-FLAIR Subtraction Digital Images to Distinguish High-Grade Glial Tumors From Brain Metastasis.

Differentiating high-grade glioma (HGG) and isolated brain metastasis (BM) is important for determining appropriate treatment. Radiomics, utilizing quantitative imaging features, offers the potential for improved diagnostic accuracy in this context. To differentiate high-grade (grade 4) glioma and BM using machine learning models from radiomics data obtained from T2-FLAIR digital subtraction images and the peritumoral edema area. Retrospective. The study included 1287 patients. Of these, 602 were male and 685 were female. Of the 788 HGG patients included in the study, 702 had solitary masses. Of the 499 BM patients included in the study, 112 had solitary masses. Initially, the model was developed and tested on solitary masses. Subsequently, the model was developed and tested separately for all patients (solitary and multiple masses). Axial T2-weighted fast spin-echo sequence (T2WI) and T2-weighted fluid-attenuated inversion recovery sequence (T2-FLAIR), using 1.5-T and 3.0-T scanners. Radiomic features were extracted from digitally subtracted T2-FLAIR images in the area of peritumoral edema. The maximum relevance-minimum redundancy (mRMR) method was then used for dimensionality reduction. The naive Bayes algorithm was used in model development. The interpretability of the model was explored using SHapley Additive exPlanations (SHAP). Chi-square test, one-way analysis of variance, and Kruskal-Wallis test were performed. The P values <0.05 were considered statistically significant. The performance metrics include area under curve (AUC), sensitivity (SENS), and specificity (SPEC). The mean age of HGG patients was 61.4 ± 13.2 years and 61.7 ± 12.2 years for BM patients. In the external validation cohort, the model achieved AUC: 0.991, SENS: 0.983, and SPEC: 0.922. The external cohort results for patients with solitary lesions were AUC: 0.987, SENS: 0.950, and SPEC: 0.922. The artificial intelligence model, developed with radiomics data from the peritumoral edema area in T2-FLAIR digital subtraction images, might be able to differentiate isolated BM from HGG. 3 TECHNICAL EFFICACY: Stage 2.

Watershed regions are more susceptible to tissue microstructural injury in multiple sclerosis.

Histopathologic studies report higher concentrations of multiple sclerosis white matter lesions in watershed areas of the brain, suggesting that areas with relatively lower oxygen levels may be more vulnerable to disease. However, it is unknown at what point in the disease course lesion predilection for watershed territories begins. Accordingly, we studied a cohort of people with newly diagnosed disease and asked whether (1) white matter lesions disproportionally localize to watershed-regions and (2) the degree of microstructural injury in watershed-lesions is more severe. Fifty-four participants, i.e. 38 newly diagnosed people with multiple sclerosis, clinically isolated syndrome or radiologically isolated syndrome, and 16 age- and sex-matched healthy controls underwent brain magnetic resonance imaging. T1-weighted and T2-weighted fluid-attenuated inversion recovery sequences, selective inversion recovery quantitative magnetisation transfer images, and the multi-compartment diffusion imaging with the spherical mean technique were acquired. We computed the macromolecular-to-free pool size ratio, and the apparent axonal volume fraction maps to indirectly estimate myelin and axonal integrity, respectively. We produced a flow territory atlas in each subject's native T2-weighted fluid-attenuated inversion recovery images using a T1-weighted magnetic resonance imaging template in the Montreal Neurological Institute 152 space. Lesion location relative to the watershed, non-watershed and mixed brain vascular territories was annotated. The same process was performed on the T2-weighted fluid-attenuated inversion recovery images of the healthy controls using 294 regions of interest. Generalized linear mixed models for continuous outcomes were used to assess differences in size, pool size ratio and axonal volume fraction between lesions/regions of interests (in healthy controls) situated in different vascular territories. In patients, we assessed 758 T2-lesions and 356 chronic black holes (cBHs). The watershed-territories had higher relative and absolute concentrations of T2-lesions (P≤0.041) and cBHs (P≤0.036) compared to either non-watershed- or mixed-zones. T2-lesions in watershed-areas also had lower pool size ratio relative to T2-lesions in either non-watershed- or mixed-zones (P = 0.039). These results retained significance in the sub-cohort of people without vascular comorbidities and when accounting for periventricular lesions. In healthy controls, axonal volume fraction was higher only in mixed-areas regions of interest compared to non-watershed-ones (P = 0.008). No differences in pool size ratio were seen. We provide in vivo evidence that there is an association between arterial vascularisation of the brain and multiple sclerosis-induced tissue injury as early as the time of disease diagnosis. Our findings underline the importance of oxygen delivery and healthy arterial vascularisation to prevent lesion formation and foster a better outcome in multiple sclerosis.

Predicting white-matter hyperintensity progression and cognitive decline in patients with cerebral small-vessel disease: a magnetic resonance-based habitat analysis.

White-matter hyperintensity (WMH) is the key magnetic resonance imaging (MRI) marker of cerebral small-vessel disease (CSVD). This study aimed to investigate whether habitat analysis based on physiologic MRI parameters can predict the progression of WMH and cognitive decline in CSVD. Diffusion- and perfusion-weighted imaging data were obtained from 69 patients with CSVD at baseline and at 1-year of follow-up. The white-matter region was classified into constant WMH, growing WMH, shrinking WMH, and normal-appearing white matter (NAWM) according to the T2-fluid-attenuated inversion recovery (FLAIR) sequences images at the baseline and follow-up. We employed k-means clustering on a voxel-wise basis to delineate WMH habitats, integrating multiple diffusion metrics and cerebral blood flow (CBF) values derived from perfusion data. The WMH at the baseline and the predicted WMH from the habitat analysis were used as regions of avoidance (ROAs). The decreased rate of global efficiency for the whole brain structural connectivity was calculated after removal of the ROA. The association between the decreased rate of global efficiency and Montreal Cognitive Assessment (MoCA) and mini-mental state examination (MMSE) scores was evaluated using Pearson correlation coefficients. We found that the physiologic MRI habitats with lower fractional anisotropy and CBF values and higher mean diffusivity, axial diffusivity, and radial diffusivity values overlapped considerably with the new WMH (growing WMH of baseline) after a 1-year follow-up; the accuracy of distinguishing growing WMH from NAWM was 88.9%±12.7% at baseline. Similar results were also found for the prediction of shrinking WMH. Moreover, after the removal of the predicted WMH, a decreased rate of global efficiency had a significantly negative correlation with the MoCA and MMSE scores at follow-up. This study revealed that a habitat analysis combining perfusion with diffusion parameters could predict the progression of WMH and related cognitive decline in patients with CSVD.

Differentiation between multifocal CNS lymphoma and glioblastoma based on MRI criteria

PurposeDifferentiating between glioblastoma (GB) with multiple foci (mGB) and multifocal central nervous system lymphoma (mCNSL) can be challenging because these cancers share several features at first appearance on magnetic resonance imaging (MRI). The aim of this study was to explore morphological differences in MRI findings for mGB versus mCNSL and to develop an interpretation algorithm with high diagnostic accuracy.MethodsIn this retrospective study, MRI characteristics were compared between 50 patients with mGB and 50 patients with mCNSL treated between 2015 and 2020. The following parameters were evaluated: size, morphology, lesion location and distribution, connections between the lesions on the fluid-attenuated inversion recovery sequence, patterns of contrast enhancement, and apparent diffusion coefficient (ADC) values within the tumor and the surrounding edema, as well as MR perfusion and susceptibility weighted imaging (SWI) whenever available.ResultsA total of 187 mCNSL lesions and 181 mGB lesions were analyzed. The mCNSL lesions demonstrated frequently a solid morphology compared to mGB lesions, which showed more often a cystic, mixed cystic/solid morphology and a cortical infiltration. The mean measured diameter was significantly smaller for mCNSL than mGB lesions (p < 0.001). Tumor ADC ratios were significantly smaller in mCNSL than in mGB (0.89 ± 0.36 vs. 1.05 ± 0.35, p < 0.001). The ADC ratio of perilesional edema was significantly higher (p < 0.001) in mCNSL than in mGB. In SWI / T2*-weighted imaging, tumor-associated susceptibility artifacts were more often found in mCNSL than in mGB (p < 0.001).ConclusionThe lesion size, ADC ratios of the lesions and the adjacent tissue as well as the vascularization of the lesions in the MR-perfusion were found to be significant distinctive patterns of mCNSL and mGB allowing a radiological differentiation of these two entities on initial MRI. A diagnostic algorithm based on these parameters merits a prospective validation.

Comparative analysis of vestibular endolymphatic hydrops grading methods and hearing loss in Ménière's disease: a retrospective MRI study using 3D-real inversion recovery sequence.

To compare the correlation between different grading methods of vestibular endolymphatic hydrops (EH) and the severity of hearing loss in Ménière's disease (MD), and evaluate the diagnostic value of these methods in diagnosing MD. This retrospective study included 30 patients diagnosed with MD from June 2021 to August 2023. All patients underwent inner ear MR gadolinium-enhanced imaging using three-dimensional (3D)-real inversion recovery sequences and pure-tone audiometry. The EH levels were independently evaluated according to the classification methods outlined by Nakashima et al. (Acta Otolaryngol Suppl 5-8, 2009. https://doi.org/10.1080/00016480902729827 ) (M1), Fang et al. (J Laryngol Otol 126:454-459, 2012. https://doi.org/10.1017/S0022215112000060 ) (M2), Barath et al. (Am J Neuroradiol 35:1387-1392, 2014. https://doi.org/10.3174/ajnr.A3856 ), (M3), Liu et al. (Front Surg 9:874971, 2022. https://doi.org/10.3389/fsurg.2022.874971 ), (M4), and Bernaerts et al. (Neuroradiology 61:421-429, 2019. https://doi.org/10.1007/s00234-019-02155-7 ) (M5), with a subsequent comparison of interobserver agreement. After achieving a consensus, an analysis was performed to explore the correlations between vestibular EH grading using different methods, the average hearing thresholds at low-mid, high-, and full frequencies and clinical stages. The diagnostic capabilities of these methods for MD were then compared. The interobserver consistency of M2-M5 was superior to that of M1. The EH grading based on M4 showed a significant correlation with the average hearing thresholds at low-mid, high-, and full frequencies and clinical stages. M1, M2, M3, and M5 correlated with some parameters. A receiver operating characteristic curve analysis indicated that M5 significantly outperformed M1, M2, M3, and M4 in terms of diagnostic efficiency for MD. M4 showed the strongest correlation with the degree of hearing loss in patients with MD, whereas M5 showed the highest diagnostic performance.

Patterns of cerebral damage in multiple sclerosis and aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders-major differences revealed by non-conventional imaging.

Multiple sclerosis and aquaporin-4 antibody neuromyelitis optica spectrum disorders are distinct autoimmune CNS disorders with overlapping clinical features but differing pathology. Multiple sclerosis is primarily a demyelinating disease with the presence of widespread axonal damage, while neuromyelitis optica spectrum disorders is characterized by astrocyte injury with secondary demyelination. Diagnosis is typically based on lesion characteristics observed on standard MRI imaging and antibody testing but can be challenging in patients with in-between clinical presentations. Non-conventional MRI techniques can provide valuable diagnostic information by measuring disease processes at the microstructural level. We used non-conventional MRI to measure markers of axonal loss in specific white matter tracts in multiple sclerosis and neuromyelitis optica spectrum disorders, depending on their relationship with focal lesions. Patients with relapsing-remitting multiple sclerosis (n = 20), aquaporin-4 antibody-associated neuromyelitis optica spectrum disorders (n = 20) and healthy controls (n = 20) underwent a 3T brain MRI, including T1-, T2- and diffusion-weighted sequences, quantitative susceptibility mapping and phase-sensitive inversion recovery sequence. Tractometry was used to differentiate tract fibres traversing through white matter lesions from those that did not. Neurite density index was assessed using neurite orientation dispersion and density imaging model. Cortical damage was evaluated using T1 relaxation rates. Cortical lesions and paramagnetic rim lesions were identified using phase-sensitive inversion recovery and quantitative susceptibility mapping. In tracts traversing lesions, only one out of 50 tracts showed a decreased neurite density index in multiple sclerosis compared with neuromyelitis optica spectrum disorders. Among 50 tracts not traversing lesions, six showed reduced neurite density in multiple sclerosis (including three in the cerebellum and brainstem) compared to neuromyelitis optica spectrum disorders. In multiple sclerosis, reduced neurite density was found in the majority of fibres traversing (40/50) and not traversing (37/50) white matter lesions when compared to healthy controls. A negative correlation between neurite density in lesion-free fibres and cortical lesions, but not paramagnetic rim lesions, was observed in multiple sclerosis (39/50 tracts). In neuromyelitis optica spectrum disorders compared to healthy controls, decreased neurite density was observed in a subset of fibres traversing white matter lesions, but not in lesion-free fibres. In conclusion, we identified significant differences between multiple sclerosis and neuromyelitis optica spectrum disorders corresponding to their distinct pathologies. Specifically, in multiple sclerosis, neurite density reduction was widespread across fibres, regardless of their relationship to white matter lesions, while in neuromyelitis optica spectrum disorders, this reduction was limited to fibres passing through white matter lesions. Further studies are needed to evaluate the discriminatory potential of neurite density measures in white matter tracts for differentiating multiple sclerosis from neuromyelitis optica spectrum disorders.

Resilience optimization of bus-metro double-layer network against extreme weather events

The resilience of bus and metro systems to extreme weather events is a critical concern in urban planning, given their growing complexity and interconnectivity. Traditional studies often simplify or overlook the interdependency between different transportation modes, focusing on recovery strategies for a single mode to enhance system resilience. This study proposes an integrated resilience assessment framework for bus and metro systems, conceptualized as a Bus-Metro Double-Layer Network (B-M DLN). The framework considers both network structure and system function to accurately evaluate the B-M DLN resilience. A resilience optimization model for B-M DLN based on Genetic Algorithm (GA) is established to suggest the optimal recovery sequence of damaged stations, emphasizing the importance of station repair time, node strength, and node degree in recovery prioritization. Through a case analysis of Xi’an City, China, the B-M DLN shows significantly enhanced resilience when applying the optimal recovery strategy, especially in large-scale failure scenarios.

Detecting optic nerve lesions in multiple sclerosis patients with a 1,5 T MRI: Evaluation of a 3D DIR sequence compared to a 2D STIR sequence

ObjectivesOptic neuritis is a common clinical presentation in patients suffering from multiple sclerosis (MS). Even though optic neuritis is not part of the MS diagnostic criteria, the diagnosis and consideration of differential diagnoses are important in clinical routine. For the evaluation of the optic nerves with MRI, T2-weighted images with fat suppression, known as short tau inversion recovery sequences (STIR), are often used. Besides that, double inversion recovery (DIR) sequences are being used increasingly in MS patients, especially to determine cortical lesions. The Aim of this study was to evaluate the 3D-DIR for the detection of lesions in the optic nerves in MS patients. MethodsMR examinations of 45 MS-patients containing both STIR and DIR images were independently assessed by two neuroradiologic experienced radiologists, blinded to clinical data. A third neuroradiologic, an experienced radiologist, evaluated the images together, also considering clinical data. These results were considered ground truth and statistically compared to the results of the single readings. To objectify our findings, ROI measurements of affected and unaffected optic nerve segments were made, and a contrast ratio (CR) was calculated. ResultDIR images are statistically equivalent to STIR images concerning the detection of lesions in the optic nerve (p < 0.001). The sensitivity of DIR images (84.7 %) and STIR images (77 %), as well as the specificity (92.2 % and 91.2 %), are comparable. The interrater reliability was substantial for both sequences (κ = 0,73) as well as separated for the STIR images (κ = 0.744) and the DIR images (κ = 0.707). The objective analysis revealed significantly higher CRs in DIR images (p < 0.001). Conclusion3D DIR images showed similar sensitivity and specificity for detecting optic nerve lesions in comparison to dedicated 2D images of the optic nerve. When 3D DIR images are part of the routine scan protocol for evaluating MS patients, additional 2D imaging of the optic nerve is no longer necessary.

Ultrafast Brain MRI at 3 T for MS: Evaluation of a 51-Second Deep Learning-Enhanced T2-EPI-FLAIR Sequence.

In neuroimaging, there is no equivalent alternative to magnetic resonance imaging (MRI). However, image acquisitions are generally time-consuming, which may limit utilization in some cases, e.g., in patients who cannot remain motionless for long or suffer from claustrophobia, or in the event of extensive waiting times. For multiple sclerosis (MS) patients, MRI plays a major role in drug therapy decision-making. The purpose of this study was to evaluate whether an ultrafast, T2-weighted (T2w), deep learning-enhanced (DL), echo-planar-imaging-based (EPI) fluid-attenuated inversion recovery (FLAIR) sequence (FLAIRUF) that has targeted neurological emergencies so far might even be an option to detect MS lesions of the brain compared to conventional FLAIR sequences. Therefore, 17 MS patients were enrolled prospectively in this exploratory study. Standard MRI protocols and ultrafast acquisitions were conducted at 3 tesla (T), including three-dimensional (3D)-FLAIR, turbo/fast spin-echo (TSE)-FLAIR, and FLAIRUF. Inflammatory lesions were grouped by size and location. Lesion conspicuity and image quality were rated on an ordinal five-point Likert scale, and lesion detection rates were calculated. Statistical analyses were performed to compare results. Altogether, 568 different lesions were found. Data indicated no significant differences in lesion detection (sensitivity and positive predictive value [PPV]) between FLAIRUF and axially reconstructed 3D-FLAIR (lesion size ≥3 mm × ≥2 mm) and no differences in sensitivity between FLAIRUF and TSE-FLAIR (lesion size ≥3 mm total). Lesion conspicuity in FLAIRUF was similar in all brain regions except for superior conspicuity in the occipital lobe and inferior conspicuity in the central brain regions. Further findings include location-dependent limitations of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) as well as artifacts such as spatial distortions in FLAIRUF. In conclusion, FLAIRUF could potentially be an expedient alternative to conventional methods for brain imaging in MS patients since the acquisition can be performed in a fraction of time while maintaining good image quality.

Can a fast T2-Dixon sequence surpass the time obstacle of whole-body MRI in the evaluation of skeletal metastases?

BackgroundWhole-body magnetic resonance imaging (WB-MRI) has shown its accuracy in the diagnosis of skeletal metastases in patients with known primary solid cancers. The standard protocol was a combination of T1 and short tau inversion recovery (STIR) sequences. Herein, this study was conducted to elucidate the role of the T2-Dixon sequence as a rapid alternative to the standard protocol with the assessment of its diagnostic accuracy and comparability to the established methodology.MethodsThis prospective study included 30 patients with primary solid malignancies who underwent WB-MRI. The sequences obtained were T1WI, STIR, and T2-Dixon (fat-only and water-only images). Skeletal metastases were evaluated in each sequence. Results were compared between the T1-STIR combination and T2-Dixon fat and water reconstructions.ResultsThe sensitivity of fat and water reconstructions from a single T2-Dixon in the detection of lytic skeletal metastases was marginally superior to a combination of T1WI and STIR sequences (0–7%). Detection of mixed lesions demonstrated equally high sensitivity in both protocols. Sclerotic metastases detection in WB-MRI showed low sensitivity in both protocols. However, specificity surpassed 95% for all lesion types in both protocols. Overall image quality was favored (in 87–90% of patients) in T2-Dixon images. The overall estimated acquisition timing using T2-Dixon appeared to be approximately half that of the standard T1-STIR combination.ConclusionsWB-MRI using T2-Dixon fat and water reconstructions showed similar accuracy to T1WI and STIR combination in the evaluation of skeletal metastases in patients with primary solid cancers with significantly shorter acquisition time.

Comparison of test-retest reproducibility of DESPOT and 3D-QALAS for water T 1 and T 2 mapping.

Relaxometry, specifically T 1 and T 2 mapping, has become an essential technique for assessing the properties of biological tissues related to various physiological and pathological conditions. Many techniques are being used to estimate T 1 and T 2 relaxation times, ranging from the traditional inversion or saturation recovery and spin-echo sequences to more advanced methods. Choosing the appropriate method for a specific application is critical since the precision and accuracy of T 1 and T 2 measurements are influenced by a variety of factors including the pulse sequence and its parameters, the inherent properties of the tissue being examined, the MRI hardware, and the image reconstruction. The aim of this study is to evaluate and compare the test-retest reproducibility of two advanced MRI relaxometry techniques (Driven Equilibrium Single Pulse Observation of T 1 and T 2, DESPOT, and 3D Quantification using an interleaved Look-Locker acquisition Sequence with a T 2 preparation pulse, QALAS), for T 1 and T 2 mapping in a healthy volunteer cohort. 10 healthy volunteers underwent brain MRI at 1.3 mm3 isotropic resolution, acquiring DESPOT and QALAS data (~11.8 and ~5 minutes duration, including field maps, respectively), test-retest with subject repositioning, on a 3.0 Tesla Philips Ingenia Elition scanner. To reconstruct the T 1 and T 2 maps, we used an equation-based algorithm for DESPOT and a dictionary-based algorithm that incorporates inversion efficiency and B 1 -field inhomogeneity for QALAS. The test-retest reproducibility was assessed using the coefficient of variation (CoV), intraclass correlation coefficient (ICC) and Bland-Altman plots. Our results indicate that both the DESPOT and QALAS techniques demonstrate good levels of test-retest reproducibility for T 1 and T 2 mapping across the brain. Higher whole-brain voxel-to-voxel ICCs are observed in QALAS for T 1 (0.84 ± 0.039) and in DESPOT for T 2 (0.897 ± 0.029). The Bland-Altman plots show smaller bias and variability of T 1 estimates for QALAS (mean of -0.02 s, and upper and lower limits of -0.14 and 0.11 s, 95% CI) than for DESPOT (mean of -0.02 s, and limits of -0.31 and 0.27 s). QALAS also showed less variability (mean 1.08 ms, limits -1.88 to 4.04 ms) for T 2 compared to DESPOT (mean of 2.56 ms, and limits -17.29 to 22.41 ms). The within-subject CoVs for QALAS range from 0.6% (T 2 in CSF) to 5.8% (T 2 in GM), while for DESPOT they range from 2.1% (T 2 in CSF) to 6.7% (T 2 in GM). The between-subject CoVs for QALAS range from 2.5% (T 2 in GM) to 12% (T 2 in CSF), and for DESPOT they range from 3.7% (T 2 in WM) to 9.3% (T 2 in CSF). Overall, QALAS demonstrated better reproducibility for T 1 and T 2 measurements than DESPOT, in addition to reduced acquisition time.

Management of patients with diffusion-weighted imaging-negative acute ischemic stroke: Retrospective analysis of 47 consecutive patients

BackgroundFew studies with a limited number of patients focused on the outcomes of patients with diffusion-weighted imaging (DWI)-negative acute ischemic stroke (AIS) after intravenous thrombolysis (IVT) and/or endovascular treatment (EVT). MethodsThis retrospective observational, single-center study included all consecutive patients admitted for AIS involving the anterior circulation and treated with IVT and/or EVT between January 1, 2015 and December 31, 2023. The collected data were used to identify the characteristics of patients with negative DWI and to compare outcomes in patients with negative and positive DWI. ResultsAmong the 1210 patients included, 47 (3.9 %) had negative (DWI-negative group) and 1163 had increased DWI signal (DWI-positive group). In the DWI-negative group, the mean age was 69 years (SD=19.4), 55.3 % were men, and 27 (57.4 %) had a large vessel occlusion. Thirty eight (80.9 %) were treated with IVT alone, 7 (14.9 %) with EVT alone, and 2 (4.3 %) with both. Fluid attenuated inversion recovery (FLAIR) sequences were the most sensitive to detect predictive factors of cerebral ischemia, such as vessel thrombosis and the spaghetti sign that were found in 68.1 % and 83 %, of patients, respectively. Oxyhemoglobin-sensitive (T2*) and susceptibility-weighted angiography (SWAN) sequences were less sensitive: vessel thrombosis and the brush sign were detected in 55.3 % and 19.1 % of patients, respectively. Comparison of the two DWI groups showed that M2 occlusion was more frequent (31.9 % vs 13 %, p<0.001) and M1 occlusion rarer (19.1 % vs 36 %, p<0.02) in the DWI-negative than DWI-positive group. At admission, the median National Institutes of Health Stroke Scale score was lower in the DWI-negative than DWI-positive group (2 vs 6, p=0.0001), but the median symptom onset-to-MRI time was similar in both groups (108 vs 111 min, p=0.88). ConclusionsIn patients with DWI-negative AIS, symptoms are less severe. Large vessel occlusions, notably in the M2 segment, are more distal at the expense of the M1 segment of MCA. The spaghetti sign remains the most predictive feature of AIS that should be specifically searched in the absence of DWI lesions.