Importance of Contrast-Enhanced Fluid-Attenuated Inversion Recovery Magnetic Resonance Imaging in Various Intracranial Pathologic Conditions

Beyond the "string of beads": case-based exploration of diagnostic pitfalls and solutions in reversible cerebral vasoconstriction syndrome

BACKGROUND

The diagnosis of reversible cerebral vasoconstriction syndrome (RCVS) is challenging due to its varied clinical manifestations and imaging findings. While it typically presents with a sudden, severe thunderclap headache and multifocal constriction of the cerebral arteries, the wide spectrum of radiological presentations may complicate the diagnosis.

MAIN BODY

This review presents a series of cases that show both typical and atypical presentations of RCVS. Typical cases show the characteristic "string of beads" pattern on angiography, which usually resolves within 3-6 months. However, diagnostic challenges arise when angiography appears normal in the early stages or when imaging artifacts obscure the findings. In addition, the variability in vasoconstriction patterns and the need for a differential diagnosis further complicate the accurate identification. These cases highlight the importance of considering RCVS in patients with recurrent thunderclap headaches, even when the initial imaging is inconclusive. Recognizing these challenges and the variability in presentation, along with the use of high-resolution vessel wall MRI and blood-brain barrier imaging, can improve diagnostic accuracy and improve patient outcomes.

CONCLUSION

The diagnosis of RCVS requires careful integration of clinical evaluation and advanced imaging techniques, with particular attention to radiological findings that can guide accurate diagnosis and management. Despite challenges, such as normal early stage angiography and imaging variability, maintaining a high suspicion of RCVS is essential, especially in patients with recurrent thunderclap headaches.

ISMRM Clinical Focus Meeting 2023: "Imaging the Fire in the Brain"

Set during the Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM), the "Clinical Focus Meeting" (CFM) aims to bridge the gap between innovative magnetic resonance imaging (MRI) scientific research and daily patient care. This initiative is dedicated to maximizing the impact of MRI technology on healthcare outcomes for patients. At the 2023 Annual Meeting, clinicians and scientists from across the globe were invited to discuss neuroinflammation from various angles (entitled "Imaging the Fire in the Brain"). Topics ranged from fundamental mechanisms and biomarkers of neuroinflammation to the role of different contrast mechanisms, including both proton and non-proton techniques, in brain tumors, autoimmune disorders, and pediatric neuroinflammatory diseases. Discussions also delved into how systemic inflammation can trigger neuroinflammation and the role of the gut-brain axis in causing brain inflammation. Neuroinflammation arises from various external and internal factors and serves as a vital mechanism to mitigate tissue damage and provide neuroprotection. Nonetheless, excessive neuroinflammatory responses can lead to significant tissue injury and subsequent neurological impairments. Prolonged neuroinflammation can result in cellular apoptosis and neurodegeneration, posing severe consequences. MRI can be used to visualize these consequences, by detecting blood-brain barrier damage, characterizing brain lesions, quantifying edema, and identifying specific metabolites. It also facilitates monitoring of chronic changes in both the brain and spinal cord over time, potentially leading to better patient outcomes. This paper represents a summary of the 2023 CFM, and is intended to guide the enthusiastic MR user to several key and novel sequences that MRI offers to image pathophysiologic processes underlying acute and chronic neuroinflammation. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 3.

Improved diagnostic accuracy for leptomeningeal dissemination in pediatric brain tumors using contrast-enhanced FLAIR imaging

Background

Central nervous system cancers are a leading cause of childhood cancer-related mortality. Accurate staging and assessment of leptomeningeal spread, particularly in aggressive neoplasms such as embryonal tumors, is crucial for treatment planning and prognosis. Conventional diagnostic methods, relying on magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) cytology, have limitations, including high false-negative rates and sensitivity issues. In this retrospective study, we aim to compare the diagnostic sensitivity of contrast-enhanced T2-weighted fluid-attenuated inversion recovery (CE-T2W-FLAIR) and 2D and 3D contrast-enhanced T1-weighted imaging (CE-T1WI) for detecting leptomeningeal disease.

Methods

We retrospectively reviewed 1372 MRI brain studies of 297 patients aged 1-19 years. We included only those MRI examinations adhering to our neuro-oncology protocol while excluding incomplete or suboptimal studies. A control group without leptomeningeal disease was matched for disease and age. Three groups of 2 neuroradiologists each, blinded to case status, reviewed the images using various sequences. The results were compared using the McNemar test and chi-squared test for P-values.

Results

The sensitivity of CE-T2W-FLAIR sequence was significantly higher compared with that of CE-T1WI (P = .025). There was no statistically significant difference between the sensitivity of 2D CE-T1WI and 3D CE-T1WI (P = .3173). The specificity of the 3D CE-T1WI was significantly lower compared with those of CE-T2W-FLAIR and 2D CE-T1WI (P = .014). The positive predictive values for CE-T2W-FLAIR, 2D CE-T1WI, and 3D CE-T1WI were 100%, 100%, and 68.4%, respectively, whereas the negative predictive values were 100%, 85.7%, and 85.71%, respectively.

Conclusions

The inclusion of CE-T2W-FLAIR in the MRI protocol improves sensitivity and specificity in diagnosing leptomeningeal spread in pediatric brain tumors.

Comparative study of 3D-T2WI vs. 3D-T2-FLAIR MRI in displaying human meningeal lymphatics vessels

AIM

Various magnetic resonance imaging (MRI) sequences can be utilized to visualize human meningeal lymphatic vessels (MLVs) for investigating the associations between MLVs and central nervous system (CNS) disorders. This study aimed to compare the quality of contrast-enhanced 3D-T2WI and 3D-T2-fluid-attenuated inversion recovery (FLAIR) MRI sequences to display human MLVs.

MATERIALS AND METHODS

Sixty-two patients (27 males, 35 females; mean age 55.8 ± 14.9 years) underwent 3D-T2WI and 3D-T2-FLAIR scan in combination with Gd-DTPA injection to show MLVs.

RESULTS

(1) The positivity rates of the 3D-T2WI sequence were 98.4%, 29.0%, and 46.8%, around the dural sinus, middle meningeal artery, and ethmoid sinus, respectively. The positivity rates of the 3D-T2-FLAIR sequence were 100%, 48.4%, and 66.1%, respectively. The positivity rate was significantly higher with the 3D-T2-FLAIR sequence compared with the 3D-T2WI sequence for the middle meningeal artery and ethmoid sinus regions (p < 0.05). (2) In patients with brain lesions and intracranial space-occupying lesions, the positivity rate was significantly higher with the 3D-T2-FLAIR sequence compared with the 3D-T2WI sequence for the middle meningeal artery and ethmoid sinus regions (p < 0.05). (3) The mean cross-sectional areas of MLVs around the dural sinus, middle meningeal artery, and ethmoid sinus were all higher using the 3D-T2-FLAIR sequence compared with the 3D-T2WI sequence at all three sites (p < 0.01). (4) The signal intensity was significantly higher using the 3D-T2-FLAIR sequence compared with the 3D-T2WI sequence around the dural sinus and ethmoid sinus (p < 0.001).

CONCLUSION

The 3D-T2-FLAIR sequence contrast-enhanced scan showed superior visualization of MLVs compared with the 3D-T2WI sequence.

Focal leptomeningeal vascular anomalies on brain MRI: A mimic of leptomeningeal metastatic disease

Background

The diagnosis of leptomeningeal metastatic disease has major prognostic and therapeutic implications. We report 13 patients with a radiologically distinct kind of focal, enhancing leptomeningeal lesion on brain MRI that mimics leptomeningeal metastatic disease.

Methods

These patients were assessed at University Health Network (Toronto, Canada) between January 2001 and December 2023.

Results

Median age was 68 years (range, 55-78 years) and 10 patients were women. All patients had brain magnetic resonance imaging (MRI) including contrast-enhanced T2-weighted fluid attenuation inversion recovery (FLAIR) and T1-weighted spin echo sequences. MRI in all 13 patients showed a focal enhancing lesion located along the leptomeningeal surface of the brain. The MRI exams were reported as possible or likely leptomeningeal metastatic disease for the majority (9/13) of patients. Each lesion was curvilinear rather than sheet-like, and some lesions consisted of multiple connected/branching curvilinear structures with the appearance of abnormal vessels. The lesions were distinct from normal blood vessels. Some lesions had a visible connection with a nearby cortical vein. Follow-up contrast-enhanced brain MRI for 8/13 (62%) patients at a median of 3.9 years (IQR 2.4-6.6 years) showed all lesions were unchanged over time. Another 2/13 (15%) patients had clinical and CT brain follow-up after one year with no evidence of metastatic disease.

Conclusions

We describe a distinct kind of focal, enhancing leptomeningeal lesion on brain MRI that mimics metastatic disease. These lesions are likely a type of low-flow vascular anomaly. Their curvilinear/branching shape and intense enhancement particularly on T2-weighted FLAIR images distinguish these lesions from tumors.

Diagnostic efficacy of contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging in idiopathic cerebrospinal fluid rhinorrhea

We report a case of a 50-year-old woman in which contrast-enhanced fluid-attenuated inversion recovery (FLAIR) was used for the diagnosis of idiopathic cerebrospinal fluid rhinorrhea. The pre- and postcontrast FLAIR subtraction images showed a contrasted protrusion of the right olfactory cleft canal, highlighting the potential practicality and effectiveness of using pre- and postcontrast FLAIR subtraction images in diagnosing idiopathic cerebrospinal fluid rhinorrhea, in conjunction with conventional high-resolution computed tomography and magnetic resonance cisternography. The successful diagnosis of cerebrospinal fluid rhinorrhea allowed for treatment through endoscopic nasal surgery to close the fistula with a positive clinical outcome.

The Diagnostic Utility of Contrast-Enhanced FLAIR Imaging in the Diagnosis of Pediatric Uveitis

Objectives: Contrast-enhanced FLAIR fat-suppressed (CE-FLAIR-FS) imaging can potentially increase the diagnostic accuracy of uveal diseases and ultimately provide better patient management. This study aimed to determine the diagnostic value of CE-FLAIR-FS imaging versus contrast-enhanced T1-weighted imaging (CE-T1WI) in the assessment of pediatric patients with uveitis. Material and methods: Twenty-one children with uveitis who underwent whole brain magnetic resonance imaging (MRI), including CE-FLAIR-FS and CE-T1WI, were retrospectively included in the study. We evaluated the presence of uveal tract contrast enhancement with thickening, vitreous humor signal abnormality, and accompanying brain abnormalities. The uveal enhancement intensity was assessed semiquantitatively as mild, moderate, and marked uveitis compared to CE-T1WI and CE-FLAIR-FS images. Results: Panuveitis (61.9%) was the most frequent anatomic location, and most of them were idiopathic (47.6%). Of the 42 eyes with clinical uveitis, enhancement of the uveal tract was observed on CE-FLAIR-FS images in 21 eyes (50%), while in 5 eyes (11.9%) on CE-T1WI. The sensitivity of CE-FLAIR-FS in panuveitis was detected to be quite high (80.8%). The number of affected eyes and enhancement degree were found to be higher on CE-FLAIR-FS (p < 0.001). In assessing the severity of uveitis, CE-FLAIR-FS grades were significantly higher and more sensitive than CE-T1WI (p < 0.001, Z: -4.347). Three patients had vitreous abnormal signals on CE-FLAIR-FS images, but none on CE-T1WI. Conclusion: CE-FLAIR-FS plays a significant role in the diagnosis of pediatric uveitis, identifying the involvement and severity of the uveal inflammation and guiding the appropriate management. It would be beneficial to add it as a standard sequence to the routine MRI protocol for uveal pathologies.

Metabolic Insight into Glioma Heterogeneity: Mapping Whole Exome Sequencing to In Vivo Imaging with Stereotactic Localization and Deep Learning

Intratumoral heterogeneity (ITH) complicates the diagnosis and treatment of glioma, partly due to the diverse metabolic profiles driven by underlying genomic alterations. While multiparametric imaging enhances the characterization of ITH by capturing both spatial and functional variations, it falls short in directly assessing the metabolic activities that underpin these phenotypic differences. This gap stems from the challenge of integrating easily accessible, colocated pathology and detailed genomic data with metabolic insights. This study presents a multifaceted approach combining stereotactic biopsy with standard clinical open-craniotomy for sample collection, voxel-wise analysis of MR images, regression-based GAM, and whole-exome sequencing. This work aims to demonstrate the potential of machine learning algorithms to predict variations in cellular and molecular tumor characteristics. This retrospective study enrolled ten treatment-naïve patients with radiologically confirmed glioma. Each patient underwent a multiparametric MR scan (T1W, T1W-CE, T2W, T2W-FLAIR, DWI) prior to surgery. During standard craniotomy, at least 1 stereotactic biopsy was collected from each patient, with screenshots of the sample locations saved for spatial registration to pre-surgical MR data. Whole-exome sequencing was performed on flash-frozen tumor samples, prioritizing the signatures of five glioma-related genes: IDH1, TP53, EGFR, PIK3CA, and NF1. Regression was implemented with a GAM using a univariate shape function for each predictor. Standard receiver operating characteristic (ROC) analyses were used to evaluate detection, with AUC (area under curve) calculated for each gene target and MR contrast combination. Mean AUC for five gene targets and 31 MR contrast combinations was 0.75 ± 0.11; individual AUCs were as high as 0.96 for both IDH1 and TP53 with T2W-FLAIR and ADC, and 0.99 for EGFR with T2W and ADC. These results suggest the possibility of predicting exome-wide mutation events from noninvasive, in vivo imaging by combining stereotactic localization of glioma samples and a semi-parametric deep learning method. The genomic alterations identified, particularly in IDH1, TP53, EGFR, PIK3CA, and NF1, are known to play pivotal roles in metabolic pathways driving glioma heterogeneity. Our methodology, therefore, indirectly sheds light on the metabolic landscape of glioma through the lens of these critical genomic markers, suggesting a complex interplay between tumor genomics and metabolism. This approach holds potential for refining targeted therapy by better addressing the genomic heterogeneity of glioma tumors.

The contribution of the meningeal immune interface to neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI) is a major cause of disability and mortality worldwide, particularly among the elderly, yet our mechanistic understanding of what renders the post-traumatic brain vulnerable to poor outcomes, and susceptible to neurological disease, is incomplete. It is well established that dysregulated and sustained immune responses elicit negative consequences after TBI; however, our understanding of the neuroimmune interface that facilitates crosstalk between central and peripheral immune reservoirs is in its infancy. The meninges serve as the interface between the brain and the immune system, facilitating important bi-directional roles in both healthy and disease settings. It has been previously shown that disruption of this system exacerbates neuroinflammation in age-related neurodegenerative disorders such as Alzheimer's disease; however, we have an incomplete understanding of how the meningeal compartment influences immune responses after TBI. In this manuscript, we will offer a detailed overview of the holistic nature of neuroinflammatory responses in TBI, including hallmark features observed across clinical and animal models. We will highlight the structure and function of the meningeal lymphatic system, including its role in immuno-surveillance and immune responses within the meninges and the brain. We will provide a comprehensive update on our current knowledge of meningeal-derived responses across the spectrum of TBI, and identify new avenues for neuroimmune modulation within the neurotrauma field.

A Case of Rheumatoid Meningitis Diagnosed with FLAIR Images and Anti-cyclic Citrullinated Peptide Antibodies Levels

Rheumatoid meningitis (RM) is a rare but serious extra-articular manifestation of rheumatoid arthritis. Due to the absence of specific biomarkers, imaging findings, or guidelines for its detection, the diagnosis of RM is difficult. This report describes a patient of RM diagnosed with an open biopsy and discusses the utility of anticyclic citrullinated peptide antibodies (ACPA) levels in the serum and cerebrospinal fluid (CSF), and contrast-enhanced (CE) fluid-attenuated inversion recovery (FLAIR) images for screening and monitoring RM. A 65-year-old woman presented with a 2-month history of headaches. Imaging studies showed asymmetric meningeal and leptomeningeal involvement seen on brain magnetic resonance imaging (MRI). An open biopsy of the meninges and leptomeninges depicted palisaded and necrotizing granulomatous inflammation, which suggests rheumatoid nodules. Treatment with prednisolone and tocilizumab led to symptom improvement and reduced lesion intensity on follow-up MRI. Throughout the treatment, the ACPA index in her serum and CSF, and the findings of CE-FLAIR images, rather than the CE T1WI, reflected disease activity. For 6 months, the patient has been stable without symptom recurrence. The ACPA index and the CE-FLAIR images were useful for the diagnosis and monitoring of RM. To validate these findings, further studies are necessary.

New-onset seizures: an unusual neurologic manifestation of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory condition primarily affecting the musculoskeletal system but can often involve other organ systems as well. Rheumatoid meningitis is a rare central nervous system (CNS) manifestation of RA characterized by pachymeningeal and leptomeningeal enhancement. Herein, we present a case of a 64-year-old male who presented with left lower extremity weakness and witnessed seizures. The diagnostic work-up, including lumbar puncture, brain MRI and meningeal biopsy ruled out malignancy and were consistent with the diagnosis of rheumatoid meningitis. The patient was discharged on high-dose steroids along with anti-seizure medications. On subsequent follow-up visits, the patient remained seizure-free.

Comparison of Diagnostic Performance between Classic and Modified Abbreviated Breast MRI and the MRI Features Affecting Their Diagnostic Performance

Abbreviated breast magnetic resonance imaging (AB-MRI) has emerged as a supplementary screening tool, though protocols have not been standardized. The purpose of this study was to compare the diagnostic performance of modified and classic AB-MRI and determine MRI features affecting their diagnostic performance. Classic AB-MRI included one pre- and two post-contrast T1-weighted imaging (T1WI) scans, while modified AB-MRI included a delayed post-contrast axial T1WI scan and an axial T2-weighted interpolated scan obtained between the second and third post-contrast T1WI scans. Four radiologists (two specialists and two non-specialists) independently categorized the lesions. The MRI features investigated were lesion size, lesion type, and background parenchymal enhancement (BPE). The Wilcoxon rank-sum test, Fisher's exact test, and bootstrap-based test were used for statistical analysis. The average area under the curve (AUC) for modified AB-MRI was significantly greater than that for classic AB-MRI (0.76 vs. 0.70, p = 0.010) in all reader evaluations, with a similar trend in specialist evaluations (0.83 vs. 0.76, p = 0.004). Modified AB-MRI demonstrated increased AUCs and better diagnostic performance than classic AB-MRI, especially for lesion size > 10 mm (p = 0.018) and mass lesion type (p = 0.014) in specialist evaluations and lesion size > 10 mm (p = 0.003) and mild (p = 0.026) or moderate BPE (p = 0.010) in non-specialist evaluations.

FLAIR hyperintensity in the subarachnoid space: Main differentials

The fluid-attenuated inversion recovery (FLAIR) sequence forms part of the vast majority of current diagnostic protocols for brain MRI. This sequence enables the suppression of the signal from cerebrospinal fluid, facilitating the detection of disease involving the subarachnoid space. The causes of hyperintensity in the arachnoid space in this sequence can be divided into two main categories: hyperintensity due to disease and hyperintensity due to artifacts. Hyperintensity due to tumors, inflammation, vascular disease, or hypercellularity of the cerebrospinal fluid or hematic contents is well known. However, numerous other non-pathological conditions, mainly due to artifacts, that are also associated with this finding are a potential source of diagnostic errors.

The visualization of hypertrophic pachymeningitis in antineutrophil cytoplasmic antibody-associated granulomatosis with polyangiitis on contrast-enhanced FLAIR

Hypertrophic pachymeningitis is a rare inflammatory condition that leads to the thickening of the dura mater, either due to unknown or identifiable secondary causes. Granulomatosis with polyangiitis is a notable causative agent, and hypertrophic pachymeningitis is the initial presentation in certain cases. The diagnosis of hypertrophic pachymeningitis is aided by contrast-enhanced MRI, although distinguishing between normal and abnormal dural enhancement can be challenging using contrast-enhanced T1WI. This study highlights the case of an 80-year-old woman diagnosed with hypertrophic pachymeningitis secondary to antineutrophil cytoplasmic antibody-associated granulomatosis with polyangiitis, where contrast-enhanced FLAIR played a crucial role in distinctly identifying abnormal dural enhancement and differentiating it from normal dura. In conclusion, although contrast-enhanced T1WI remains indispensable, contrast-enhanced FLAIR can serve as a valuable complementary tool in MRI study sequences for the diagnosis of hypertrophic pachymeningitis.

Utility of contrast-enhanced 3D STIR FLAIR imaging for evaluating pituitary adenomas at 3 Tesla

Purpose

To assess the usefulness of contrast-enhanced 3D STIR FLAIR imaging for evaluation of pituitary adenomas.

Methods

Patients with pituitary adenomas underwent MR examinations including contrast-enhanced 3D STIR FLAIR and 2D T1-weighted (T1W) imaging. We subjectively compared the two techniques in terms of 10 categories. In addition, images were rated by side-by-side comparisons into three outcomes: 3D STIR FLAIR imaging superior, equal, or 2D T1W imaging superior. Additionally, the added value of 3D STIR FLAIR imaging for adenoma detection over conventional MR imaging was assessed.

Results

Twenty-one patients were included in this study. 3D STIR FLAIR imaging offered significantly better images than 2D T1W imaging in terms of three categories, including overall visualization of the cranial nerves in the cavernous sinus (mean 4.0 vs. 2.8, p < 0.0001), visualization of the optic nerves and chiasm (mean 4.0 vs. 2.6, p < 0.0001), and severity of susceptibility artifacts (mean 0.0 vs. 0.4, p = 0.004). In the side-by-side comparison, 3D STIR FLAIR imaging was judged to be significantly superior to 2D T1W imaging for overall lesion conspicuity (62% vs. 19%, p = 0.049) and border between the adenoma and the pituitary gland (67% vs. 19%, p = 0.031). The addition of 3D STIR FLAIR imaging significantly improved the adenoma detection of conventional MR imaging.

Conclusion

3D STIR FLAIR imaging improved overall lesion conspicuity compared to 2D T1W imaging. We suggest that 3D STIR FLAIR imaging is recommended as a supplemental technique when pituitary adenomas are invisible or equivocal on conventional imaging.

Diagnostic value of contrast-enhanced 3D FLAIR sequence in acute optic neuritis

PURPOSE

Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) sequence of the brain has the potential for detecting optic nerve abnormality. This study aimed to compare the diagnostic value of whole-brain contrast-enhanced three-dimensional FLAIR with fat suppression (CE 3D FLAIR FS) sequence in detecting acute optic neuritis to dedicated orbit MRI and clinical diagnosis.

MATERIALS AND METHODS

Twenty-two patients with acute optic neuritis who underwent whole-brain CE-3D-FLAIR FS and dedicated orbit MRI were retrospectively included. The hypersignal FLAIR of the optic nerve on whole-brain CE-3D-FLAIR FS, enhancement, and hypersignal T2W on orbit images were assessed. The optic nerve to frontal white matter signal intensity ratio on CE-FLAIR FS was calculated as maximum signal intensity ratio (SIR) and mean SIR.

RESULTS

Twenty-six hypersignals of optic nerves were found on CE-FLAIR FS from 30 pathologic nerves. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CE FLAIR FS brain and dedicated orbital images for diagnosing acute optic neuritis were 77%, 93%, 96%, 65%, and 82% and 83%, 93%, 96%, 72%, and 86%, respectively. Optic nerve to frontal white matter SIR of the affected optic nerves was higher than that of normal optic nerves. Using a cutoff maximum SIR of 1.24 and cutoff mean SIR of 1.16, the sensitivity, specificity, PPV, NPV, and accuracy were 93%, 86%, 93%, 80%, and 89% and 93%, 86%, 93%, 86%, and 91%, respectively.

CONCLUSION

The hypersignal of the optic nerve on whole-brain CE 3D FLAIR FS sequence has qualitative and quantitative diagnostic potential in patients with acute optic neuritis.

Noninvasive investigations of human glymphatic dynamics in a diseased model

OBJECTIVES

To explore human glymphatic dynamics in a diseased model via a noninvasive technique.

METHODS

Patients with reversible vasoconstriction syndrome (RCVS) presenting with blood-brain barrier disruption, i.e., para-arterial gadolinium leakage on 3-T 3-dimensional isotropic contrast-enhanced T2-fluid-attenuated inversion recovery (CE-T2-FLAIR) magnetic resonance imaging (MRI), were prospectively enrolled. Consecutive 9-min-CE-T2-FLAIR for 5-6 times (early panel) after intravenous gadolinium-based contrast agent (GBCA) administration and one time-varying deferred scan of noncontrast T2-FLAIR (delayed panel) were performed. In Bundle 1, we measured the calibrated signal intensities (cSIs) of 10 different anatomical locations. In Bundle 2, brain-wide measurements of para-arterial glymphatic volumes, means, and medians of the signal intensities were conducted. We defined mean (mCoIs) or median (mnCoIs) concentration indices as products of volumes and signal intensities.

RESULTS

Eleven subjects were analyzed. The cSIs demonstrated early increase (9 min) in perineural spaces: (cranial nerve [CN] V, p = 0.008; CN VII + VII, p = 0.003), choroid plexus (p = 0.003), white matter (p = 0.004) and parasagittal dura (p = 0.004). The volumes, mCoIs, and mnCoIs demonstrated increasing rates of enhancement after 9 to 18 min and decreasing rates after 45 to 54 min. The GBCA was transported centrifugally and completely removed within 961-1086 min after administration.

CONCLUSIONS

The exogenous GBCA leaked into the para-arterial glymphatics could be completely cleared around 961 to 1086 min after administration in a human model of BBB disruption. The tracer enhancement started variously in different intracranial regions but was eventually cleared centrifugally to brain convexity, probably towards glymphatic-meningeal lymphatics exits.

CLINICAL RELEVANCE STATEMENT

Glymphatic clearance time intervals and the centrifugal directions assessed by a noninvasive approach may have implications for clinical glymphatic evaluation in the near future.

KEY POINTS

• This study aimed to investigate the human glymphatic dynamics in a noninvasive diseased model. • The intracranial MR-detectable gadolinium-based contrast agents were removed centrifugally within 961 to 1086 min. • The glymphatic dynamics was demonstrable by enhancing MRI in an in vivo diseased model noninvasively.

Comparison of post contrast fluid attenuated inversion recovery, 3D T1-SPACE, and T1W MRI sequences with fat suppression in the diagnosis of infectious meningitis

OBJECTIVE

To assess the usefulness of post contrast Fluid attenuated inversion recovery (FLAIR), 3D T1-SPACE, and T1W magnetic resonance imaging (MRI) sequences with fat suppression in diagnosis of infectious meningitis.

METHODS

75 patients with clinical suspicion of meningitis were evaluated with post contrast FLAIR (PC-FLAIR), post contrast T1-SPACE (PC-T1-SPACE), and post contrast T1WI (PC-T1WI). Sensitivity, specificity, positive predictive value, and negative predictive value of individual sequences were assessed.

RESULTS

The sensitivity of PC-FLAIR (88.4%) was greater than PC-T1-SPACE (85.5%) and PC-T1WI (82.6%), considering cerebrospinal fluid (CSF) analysis as gold standard (p < 0.05). Kappa inter-rater agreement between two radiologists was 0.921 for PC-T1-SPACE, 0.921 for PC-T1WI, and 1.0 for PC-FLAIR with a p value <0.05. Both PC-T1-SPACE and PC-FLAIR performed equally in sulcal space enhancement. PC-T1-SPACE and PC-T1WI performed better in evaluation of pachymeningeal enhancement, ependymal enhancement in cases of ventriculitis, whereas PC-FLAIR was more sensitive in assessment of basal cistern enhancement and enhancement along the cerebellar folia.

CONCLUSION

Meningeal enhancement could be better appreciated in PC-FLAIR image than PC-T1WI and PC-T1-SPACE. Enhancement in PC-T1-SPACE was comparable to that of PC-T1WI. Being a T1 based spin echo sequence, PC-T1-SPACE has all the advantages of PC-T1WI in addition to its ability to differentiate meningeal enhancement from leptomeningeal vessels. Hence, PC-T1WI can be replaced by PC-T1-SPACE and PC-FLAIR can be added to routine MRI protocol in suspected case of meningitis.

Segmentation of Brain Metastases Using Background Layer Statistics (BLAST)

BACKGROUND AND PURPOSE

Accurate segmentation of brain metastases is important for treatment planning and evaluating response. The aim of this study was to assess the performance of a semiautomated algorithm for brain metastases segmentation using Background Layer Statistics (BLAST).

MATERIALS AND METHODS

Nineteen patients with 48 parenchymal and dural brain metastases were included. Segmentation was performed by 4 neuroradiologists and 1 radiation oncologist. K-means clustering was used to identify normal gray and white matter (background layer) in a 2D parameter space of signal intensities from postcontrast T2 FLAIR and T1 MPRAGE sequences. The background layer was subtracted and operator-defined thresholds were applied in parameter space to segment brain metastases. The remaining voxels were back-projected to visualize segmentations in image space and evaluated by the operators. Segmentation performance was measured by calculating the Dice-Sørensen coefficient and Hausdorff distance using ground truth segmentations made by the investigators. Contours derived from the segmentations were evaluated for clinical acceptance using a 5-point Likert scale.

RESULTS

The median Dice-Sørensen coefficient was 0.82 for all brain metastases and 0.9 for brain metastases of ≥10 mm. The median Hausdorff distance was 1.4 mm. Excellent interreader agreement for brain metastases volumes was found with an intraclass correlation coefficient = 0.9978. The median segmentation time was 2.8 minutes/metastasis. Forty-five contours (94%) had a Likert score of 4 or 5, indicating that the contours were acceptable for treatment, requiring no changes or minor edits.

CONCLUSIONS

We show accurate and reproducible segmentation of brain metastases using BLAST and demonstrate its potential as a tool for radiation planning and evaluating treatment response.

The Use of Contrast-Enhanced Ultrasound (CEUS) in the Evaluation of the Neonatal Brain

In recent years, advancements in technology have allowed the use of contrast-enhanced ultrasounds (CEUS) with high-frequency transducers, which in turn, led to new possibilities in diagnosing a variety of diseases and conditions in the field of radiology, including neonatal brain imaging. CEUSs overcome some of the limitations of conventional ultrasounds (US) and Doppler USs. It allows the visualization of dynamic perfusion even in the smallest vessels in the whole brain and allows the quantitative analysis of perfusion parameters. An increasing number of articles are published on the topic of the use of CEUSs on children each year. In the area of brain imaging, the CEUS has already proven to be useful in cases with clinical indications, such as hypoxic-ischemic injuries, stroke, intracranial hemorrhages, vascular anomalies, brain tumors, and infections. We present and discuss the basic principles of the CEUS and its safety considerations, the examination protocol for imaging the neonatal brain, and current and emerging clinical applications.

Application of Metabolic Reprogramming to Cancer Imaging and Diagnosis

Cellular metabolism governs the signaling that supports physiological mechanisms and homeostasis in an individual, including neuronal transmission, wound healing, and circadian clock manipulation. Various factors have been linked to abnormal metabolic reprogramming, including gene mutations, epigenetic modifications, altered protein epitopes, and their involvement in the development of disease, including cancer. The presence of multiple distinct hallmarks and the resulting cellular reprogramming process have gradually revealed that these metabolism-related molecules may be able to be used to track or prevent the progression of cancer. Consequently, translational medicines have been developed using metabolic substrates, precursors, and other products depending on their biochemical mechanism of action. It is important to note that these metabolic analogs can also be used for imaging and therapeutic purposes in addition to competing for metabolic functions. In particular, due to their isotopic labeling, these compounds may also be used to localize and visualize tumor cells after uptake. In this review, the current development status, applicability, and limitations of compounds targeting metabolic reprogramming are described, as well as the imaging platforms that are most suitable for each compound and the types of cancer to which they are most appropriate.

Contrast enhanced FLAIR versus contrast enhanced T1W images in evaluation of intraparenchymal brain lesions

Background

Patients with suspected brain lesions are usually evaluated by means of intravenous contrast materials. These lesions may demonstrate enhancement through different mechanisms. At most institutions, CE-T1WI is the preferred sequence. FLAIR is a sort of inversion recovery pulse sequence with a long TR, TE and T1 and hence effectually nulls signals from CSF. The long T1 causes mild T effect and this result in lesion enhancement on post-contrast study. Therefore, lesions demonstrating enhancement on CE-T1WI will also demonstrate enhancement on CE-FLAIR images. The purpose of this work was to assess the role of CE-FLAIR versus CE-T1WI in evaluation of different intraparenchymal brain lesions.

Results

Comparing CE-T1WI to CE-FLAIR in various brain pathologies, both observers found higher sensitivity and specificity for lesion to background contrast ratio on CE-FLAIR comparing to CE-T1WI. Observer 1 found that lesion to background contrast ratio on CE-FLAIR had sensitivity of 71.4%, specificity of 66.7% and AUC of 0.661 versus 63.3% sensitivity, 58.3% specificity and 0.634 AUC for CE-T1WI. Observer 2 found that lesion to background contrast ratio on CE-FLAIR had sensitivity of 77.6%, specificity of 66.7% and AUC of 0.719 versus 61.2% sensitivity, 50% specificity and 0.628 AUC for CE-T1WI.

Conclusion

On comparing CE-FLAIR to CE-T1WI, CE-FLAIR display better lesion detection and enhancement also better soft tissue contrast resolution.

Added value of delayed post-contrast FLAIR in diagnosis of metastatic brain lesions

Background

One of the drawbacks in contrast-enhanced T1-weighted imaging (CE-T1WI) is the enhancing cortical vessels which can be confused with meningeal enhancement. Previous studies reported that post-contrast FLAIR could be better for diagnosing the superficial brain abnormalities. So the purpose of this study was to evaluate the role of delayed post-contrast FLAIR, in comparison with post-contrast T1, in the detection and evaluation of brain metastases.

Results

The study was conducted on 40 patients with suspected/known brain metastases scanned in order to detect and evaluate brain metastases. All patients were subjected to the following: full history taking, review of clinical examination reports, and other imaging modalities whenever available, followed by brain MRI examination using 1.5 T closed magnet including pre-contrast series, axial and sagittal T1-weighted spin echo (SE), axial and coronal T2-weighted turbo spin echo (TSE) and axial FLAIR, while post-contrast series included axial, coronal and sagittal T1-weighted spin echo (SE) and lastly DPC-FLAIR sequence 10 min after contrast administration. This study included 18 males and 22 females, ranging in age from 26 to 75 years. Six out of a total of 40 patients had brain metastases of unknown origin, while 34 of them were presented with different types of known primary tumors. The detected lesions were subdivided into five groups according to their detectability by DPC-FLAIR and contrast-enhanced T1WI: Group (I): lesions detected only by DPC-FLAIR: 16 lesions; Group (II): lesions detected only by CE-T1WI: 1 lesion; Group (III): lesions detected by both DPC-FLAIR and CE-T1WI with equal conspicuity by both: 28 lesions; Group (IV): lesions detected by both, showing more obvious enhancement with DPC-FLAIR: 43 lesions; and Group (V): lesions detected by both, showing more obvious enhancement with CE-T1WI: 11 lesions. DPC-FLAIR had a sensitivity of 98.98% and a specificity of 100% for the detection of metastatic brain lesions and for CE-T1WI; sensitivity of 83.83%; and a specificity of 50%.

Conclusions

Delayed post-contrast FLAIR is a reliable sequence for the detection of metastatic brain lesions as it can detect more metastatic brain lesions compared to contrast-enhanced T1WI.

Normal Enhancement within the Vestibular Aqueduct: An Anatomic Review with High-Resolution MRI

BACKGROUND AND PURPOSE

The normal appearance of the vestibular aqueduct on postcontrast MR images has not been adequately described in the literature. This study set out to characterize the expected appearance of the vestibular aqueduct, with particular emphasis on the enhancement of the structure on both 3D FSE T1 and 3D-FLAIR sequences.

MATERIALS AND METHODS

All MR imaging examinations of the internal auditory canals performed between March 1, 2021, and May 20, 2021, were retrospectively reviewed. All studies included high-resolution (≤0.5-mm section thickness) pre- and postgadolinium 3D FSE T1 with fat-saturated and postgadolinium 3D-FLAIR sequences. Two neuroradiologists independently reviewed the MR images of the vestibular aqueduct for the presence or absence of enhancement on both T1 and FLAIR images and compared the relative intensity of enhancement between sequences. The presence or absence of an enlarged vestibular aqueduct was also noted.

RESULTS

Ninety-five patients made up the patient cohort, of whom 5 did not have postcontrast FLAIR images available (50 women [55.6%]). On both sides, enhancement was significantly more commonly seen on postgadolinium FLAIR (76/180, 42.2%) than on T1 fat-saturated images (41/190, 21.6%) (P < .001). The intensity of enhancement was significantly greater on postgadolinium FLAIR images than on T1 fat-saturated images (38.9% versus 3.7%, respectively; P < .001).

CONCLUSIONS

Enhancement within the vestibular aqueduct is an expected finding on MR imaging and is both more common and more intense on postgadolinium 3D-FLAIR than on T1 fat-saturated sequences. Such enhancement should not be confused with pathology on MR imaging unless other suspicious findings are present.

Imaging finding and analysis of brain lymphoma in contrast-enhanced fluid attenuated inversion recovery sequence

OBJECTIVE

The purpose of this retrospective study was to report and analyze the image findings of contrast-enhanced fluid-attenuated inversion recovery (CE-FLAIR) sequence of lymphoma in the brain.

MATERIAL AND METHODS

Thirty-two immunocompetent patients with biopsy-proven diffuse large B-cell type lymphoma in the brain were evaluated with pre-treatment MRI examinations from August 2014 to April 2020. As stereotactic studies on the day of biopsy, FLAIR and T1-weighted axial images were acquired in 2 mm thickness, before and after administrating gadolinium-based contrast agents, with 3.0 Tesla MR machines. Respective subtraction images were also obtained for both CE-FLAIR and contrast-enhanced T1-wieghted image (CE-T1WI) sequences. The imaging findings, especially the enhancement pattern on CE-FLAIR sequence, were analyzed qualitatively and quantitatively, using semi-automatic segmentation.

RESULTS

On CE-FLAIR images, brain lymphomas were poorly enhanced, while showing peripheral rim enhancement (54 of 58 lesions, 93.1 %) and central enhancing foci (40 of 58 lesions, 69.0 %). Seventy percent of central enhancing foci were correlated to areas with low signal intensity on CE-T1WI. In quantitative analysis, the mean signal intensity of CE-T1WI subtraction was 490.44 and that of FLAIR subtraction was 206.13. The standard deviation of all signal intensity values in CE-T1WI subtraction sequence was 143.45, while that of CE-FLAIR subtraction sequence was 118.41.

CONCLUSION

On CE-FLAIR, brain lymphomas showed relatively poor and homogeneous enhancement, when compared to CE-T1WI. Most brain lymphomas displayed peripheral rim enhancement and central enhancing foci.

Isolated Leptomeningeal Enhancement in Anti-N-Methyl D-Aspartate Receptor Encephalitis: The Diagnostic Value of Contrast-Enhanced Fluid-Attenuated Inversion Recovery Imaging

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a common autoimmune encephalitis that is noted to be a severe but treatable disease entity. Patients with anti-NMDAR encephalitis often develop psychotic symptoms, including delusions, hallucinations, and paranoia, as well as memory impairment and persistent loss of attention. However, MRI findings in such patients show no abnormalities in most cases. Although typical brain abnormality features, known as T2 hyperintensities, involve the brain parenchyma and contrast enhancement at the cerebral cortex or overlying meninges, isolated leptomeningeal enhancement has been rarely reported in anti-NMDAR encephalitis. Herein, we report a patient with anti-NMDAR encephalitis who presented with isolated leptomeningeal enhancement, additionally showing the diagnostic value of contrast-enhanced fluid-attenuated inversion recovery imaging.

Practical Genetics for the Neuroradiologist: Adding Value in Neurogenetic Disease

Genetic discoveries have transformed our understanding of many neurologic diseases. Identification of specific causal pathogenic variants has improved understanding of pathophysiology and enabled replacement of many confusing eponyms and acronyms with more meaningful and clinically relevant genetics-based terminology. In this era of rapid scientific advancement, multidisciplinary collaboration among pediatricians, neurologists, geneticists, radiologists, and other members of the health care team is increasingly important in the care of patients with genetic neurologic diseases. Radiologists familiar with neurogenetic disease add value by (1) recognizing constellations of characteristic imaging findings that are associated with a genetic disease before one is clinically suspected; (2) predicting the most likely genotypes for a given imaging phenotype in clinically suspected genetic disease; and (3) providing detailed and accurate descriptions of the imaging phenotype in challenging cases with unknown or uncertain genotypes. This review aims to increase awareness and understanding of pathogenic variants relating to neurologic disease by (1) briefly reviewing foundational knowledge of chromosomes, inheritance patterns, and mutagenesis; (2) providing concrete examples of and detailed information about specific neurologic diseases resulting from pathogenic variants; and (3) highlighting clinical and imaging features that are of greatest relevance for the radiologist.

Contrast-Enhanced Fluid-Attenuated Inversion Recovery in Neuroimaging: A Narrative Review on Clinical Applications and Technical Advances

While contrast-enhanced fluid-attenuated inversion recovery (FLAIR) has long been regarded as an adjunct sequence to evaluate leptomeningeal disease in addition to contrast-enhanced T1-weighted imaging, it is gradually being used for more diverse pathologies beyond leptomeningeal disease. Contrast-enhanced FLAIR is known to be highly sensitive to low concentrations of gadolinium within the fluid. Accordingly, recent research has suggested the potential utility of contrast-enhanced FLAIR in various kinds of disease, such as Meniere's disease, seizure, stroke, traumatic brain injury, and brain metastasis, in addition to being used for visualizing glymphatic dysfunction. However, its potential applications have been reported sporadically in an unorganized manner. Furthermore, the exact mechanism for its superior sensitivity to low concentrations of gadolinium has not been fully understood. Rapidly developing magnetic resonance technology and unoptimized parameters for FLAIR may challenge its accurate application in clinical practice. This review provides the fundamental mechanism of contrast-enhanced FLAIR, systematically describes its current and potential clinical application, and elaborates on technical considerations for its optimization. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 5.

The Clinical Significance of the Hyperintense Acute Reperfusion Marker Sign in Subacute Infarction Patients

Purpose: The hyperintense acute reperfusion marker (HARM) is characterized by the delayed enhancement of the subarachnoid or subpial space observed on postcontrast fluid-attenuated inversion recovery (FLAIR) images, and is considered a cerebral reperfusion marker for various brain disorders, including infarction. In this study, we evaluated the cerebral distribution patterns of HARM for discriminating between an enhancing subacute infarction and an enhancing mass located in the cortex and subcortical white matter. Materials and methods: We analyzed consecutive patients who experienced a subacute ischemic stroke, were hospitalized, and underwent conventional brain magnetic resonance imaging including postcontrast FLAIR within 14 days from symptom onset, as well as those who had lesions corresponding to a clinical sign detected by diffusion-weighted imaging and postcontrast T1-weighted imaging between May 2019 and May 2021. A total of 199 patients were included in the study. Of them, 94 were finally included in the subacute infarction group. During the same period, 76 enhancing masses located in the cortex or subcortical white matter, which were subcategorized as metastasis, malignant glioma, and lymphoma, were analyzed. We analyzed the overall incidence of HARM in subacute ischemic stroke cases, and compared the enhancement patterns between cortical infarctions and cortical masses. Results: Among 94 patients with subacute stroke, 78 patients (83%) presented HARM, and among 76 patients with subcortical masses, 48 patients (63%) presented peripheral rim enhancement. Of 170 subcortical enhancing lesions, 88 (51.8%) showed HARM, and 78 (88.6%) were determined to be subacute infarction. Among 94 patients with subacute stroke, 48 patients (51%) had diffusion restrictions, and HARM was found in 39 patients (81.2%). Of the 46 patients (49%) without diffusion restriction, 39 patients (84.8%) showed HARM. Conclusions: The presence of HARM was significantly associated with subacute infarctions. For the masses, a peripheral rim enhancement pattern was observed around the mass rather than the cerebral sulci on postcontrast FLAIR.

Role of contrast-enhanced FLAIR MRI in diagnosis of intracranial lesions

Background

MR imaging plays a significant role in detection and characterization of different brain diseases. The role of the post-contrast T1-weighted image magnetic resonance imaging (T1W MRI) sequence has been widely established in previous studies and clinical practice. In this study, we aim to share our experience as regards the added value of contrast-enhanced fluid-attenuated inversion recovery (CE-FLAIR) sequence in the diagnosis of various intracranial pathological conditions and evaluate its usefulness in comparison with post-contrast T1W images.

Results

Based on the final radiological diagnosis, the total cases were subdivided into three categories, and the majority of our cases were tumors (81.2%), followed by multiple sclerosis (11.8%), and the least was central nervous system infection (7.1%). CE-FLAIR showed superior enhancement in 35 cases (50.7) and equal enhancement in 25 cases (36.3%). However, it showed less enhancement than post-contrast T1W images in 9 cases (13%). Excellent inter-observer agreement (97.65%) was noted. Regarding lesion conspicuity, good delineation was found in the majority of cases (64.7%), fair delineation in 12.9%, and no delineation in 22.4%. A statistically significant difference was found in signal intensity of lesion between pre- and post-contrast FLAIR sequences. Contrast to background ratio was statistically significant in CE FLAIR images in comparison to CE T1 images.

Conclusion

CE-FLAIR imaging should be used as a routine or adjunctive sequence to CE-T1WI to enhance early detection and increase the diagnostic confidence in MRI examination of different brain pathological conditions.

Enhancement of subarachnoid space during magnetic resonance imaging of endolymphatic hydrops: a case report

Enhancement of the subarachnoid space after intravenous administration of gadolinium contrast agent is not common. Enhancement usually occurs in pathological conditions that increase the permeability of the blood–cerebrospinal fluid barrier, most notably in meningitis. We herein describe possible subarachnoid enhancement in patients with no apparent effect on the meninges. These patients had clinical signs of Meniere’s disease and underwent specific magnetic resonance imaging of the inner ear to possibly visualize endolymphatic hydrops. The endolymphatic space can be noninvasively imaged by intravenous administration of contrast agent, usually at a double dose, 4 hours before the scanning process. During this time, the contrast agent penetrates not only the perilymph but also the subarachnoid space, where the highest concentration occurs after 4 hours according to some studies.

Pediatric midline H3K27M-mutant tumor with disseminated leptomeningeal disease and glioneuronal features: case report and literature review

BACKGROUND

H3K27M-mutant midline lesions were recently reclassified by the World Health Organization (WHO) as "diffuse midline glioma" (DMG) based entirely on their molecular signature. DMG is one of the most common and most lethal pediatric brain tumors; terminal progression is typically caused by local midbrain or brainstem progression, or secondary leptomeningeal dissemination. H3K27M mutations have also been infrequently associated with a histologically and prognostically diverse set of lesions, particularly spinal masses with early leptomeningeal spread.

CASE PRESENTATION

A 15-year-old girl after 1 week of symptoms was found to have a T2/FLAIR-hyperintense and contrast-enhancing thalamic mass accompanied by leptomeningeal enhancement along the entire neuraxis. Initial infectious workup was negative, and intracranial biopsy was inconclusive. Spinal arachnoid biopsy revealed an H3K27M-mutant lesion with glioneuronal features, classified thereafter as DMG. She received craniospinal irradiation with a boost to the thalamic lesion. Imaging 1-month post-radiation demonstrated significant treatment response with residual enhancement at the conus.

CONCLUSIONS

This case report describes the unique presentation of an H3K27M-mutant midline lesion with significant craniospinal leptomeningeal spread on admission and atypical glioneuronal histopathological markers. With such florid leptomeningeal disease, spinal dural biopsy should be considered earlier given its diagnostic yield in classifying the lesion as DMG. Consistent with similar prior reports, this lesion additionally demonstrated synaptophysin positivity-also potentially consistent with a diagnosis of diffuse leptomeningeal glioneuronal tumor (DLGNT). In atypical DMG cases, particularly with leptomeningeal spread, further consideration of clinical and histopathological context is necessary for accurate diagnosis and prognostication.

Enhancement degree of brain metastases: correlation analysis between enhanced T2 FLAIR and vascular permeability parameters of dynamic contrast-enhanced MRI

OBJECTIVES

To investigate the correlation between enhancement degrees of brain metastases on contrast-enhanced T2-fluid-attenuated inversion recovery (CE-T2 FLAIR) and vascular permeability parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

METHODS

Thirty-nine patients with brain metastases were prospectively collected. They underwent non-enhanced T2 FLAIR, DCE-MRI, CE-T2 FLAIR, and contrast-enhanced three-dimensional brain volume imaging (CE-BRAVO). Quantitative parameters of DCE-MRI were evaluated for all lesions, which included volume transfer constant (K^trans), rate constant (K_ep), and fractional volume of the extracellular extravascular space (V_e). Contrast ratio (CR) and percentage increase (PI) values of all lesions on CE-T2 FLAIR were also measured. The tumor enhancement degree on CE-T2 FLAIR in relation to CE-BRAVO was visually classified as higher (group A), equal (group B), and lower (group C).

RESULTS

A total of 82 brain metastases were evaluated, including 31 in group A, 19 in group B, and 32 in group C. The K^trans and K_ep were negatively correlated with the CR (ρ = - 0.551, p < 0.001 and ρ = - 0.708, p < 0.001, respectively) and PI (ρ = - 0.511, p < 0.001 and ρ = - 0.621, p < 0.001, respectively). The K^trans and K_ep of group A were significantly lower than those of group C (both p < 0.001). No significant difference was found in V_e among the groups (p = 0.327).

CONCLUSIONS

The enhancement degree of brain metastases on CE-T2 FLAIR is negatively correlated with K^trans and K_ep values, which indicate that vascular permeability parameters may play an important role in explaining the difference in enhancement between CE-T2 FLAIR and CE-BRAVO.

KEY POINTS

• The enhancement degree on CE-T2 FLAIR was negatively correlated with K^trans and K_ep values. • The vascular permeability of brain metastasis accounted for the difference in enhancement degree between CE-T2 FLAIR and CE-BRAVO. • CE-T2 FLAIR is useful for detecting brain metastases with mild disruption of the blood-brain barrier.

High-resolution MR imaging of cranial neuropathy in patients with anti-GQ1b antibody syndrome

OBJECTIVE

The value of conventional MRI in patients anti-GQ1b antibody syndrome is subject to debate. Our purpose was to evaluate the diagnostic accuracy of high-resolution MRI for detecting cranial nerve abnormalities in patients with anti-GQ1b antibody syndrome.

MATERIALS AND METHODS

This retrospective cohort study enrolled 15 anti-GQ1b-positive patients diagnosed with MFS and related disorders and 17 age-matched controls, all of whom underwent high-resolution MR imaging including pre-contrast and contrast-enhanced (CE) 3D FLAIR and 3D CE T1-weighted turbo field echo (T1-TFE) between 2010 and 2016. The diagnostic performance of high-resolution MRI was assessed using the area under the curve (AUC) of the receiver operating characteristics curve. Inter- and intraobserver agreements were calculated using kappa statistics and intraclass correlation coefficients (ICC), respectively.

RESULTS

Ophthalmoplegia, ataxia, and hypo/areflexia were present in 100%, 60%, and 67%, respectively. Other neurologic findings included ptosis (40%), mydriasis (13%), and facial (27%) and bulbar (13%) palsy. Fourteen of sixteen (88%) MR examinations in 15 patients demonstrated at least one cranial nerve abnormality corresponding to the clinical findings. The involved cranial nerves on MRI were the IIIrd cranial nerve in 14 patients, VIth in nine, VIIth in four, Vth in one, and VIIIth in one. AUC values for detecting cranial neuropathy on high-resolution MRI were 0.938 (95% CI: 0.795-0.992) on a per patient basis. Inter- and intraobserver agreements were 0.842 and 0.945, respectively.

CONCLUSION

High-resolution 3D FLAIR and CE 3D T1-TFE MRI has high reliability and accuracy for demonstrating cranial neuropathy in patients with anti-GQ1b antibody syndrome.

Optimization of Contrast Agent Dosage on Contrast-Enhanced T2 Fluid-Attenuated Inversion Recovery: An In Vitro and In Vivo Study

OBJECTIVE

This study aimed to ascertain the minimum gadolinium dosage on contrast-enhanced (CE) T2 fluid-attenuated inversion recovery (FLAIR) at appropriate imaging time.

METHODS

Different dosages of gadodiamide were imaged with a 3.0-T magnetic resonance scanner for T2-FLAIR and T1WI. Twenty glioma-induced rat models were randomly assigned into 4 groups (1/2, 1/4, 1/6, 1/8 of routine dosage) and imaged for T2-FLAIR and T1WI preinjection and postinjection of gadodiamide. Contrast-enhanced T2-FLAIR was acquired for 8 repetitions postinjection. Enhancement effects were assessed by calculating contrast-noise ratio and contrast ratio using Kruskal-Wallis and Mann-Whitney rank sum test.

RESULTS

The in vitro experiment showed that gadodiamide at 1/4 of the T1WI dosage presented the best contrast on CE-T2-FLAIR. For in vivo study, the best enhancement effect on CE-T2-FLAIR was achieved at 1/2 of the routine dosage at 8 to 12 minutes of delayed scanning. Compared with CE-T1WI at routine dosage, CE-T2-FLAIR at 1/2 gadodiamide dosage presented similar enhancement effects with no statistical difference (P = 0.244 and 0.090 for contrast-noise ratio and contrast ratio, respectively).

CONCLUSIONS

Contrast-enhanced T2-FLAIR imaging with half of T1WI routine gadodiamide dosage can produce similar enhancement effects to CE-T1WI when characterizing brain gliomas. The cut-down of contrast agent dosage may help reduce gadolinium accumulation in certain tissues.

The value of contrast-enhanced FLAIR magnetic resonance imaging in detecting meningeal abnormalities in suspected cases of meningitis compared to conventional contrast-enhanced T1WI sequences

Background

Early diagnosis of meningitis with magnetic resonance imaging (MRI) would be useful for appropriate and effective management, decrease morbidity and mortality, and provide better diagnosis and treatment. The objective of the current study is to compare the accuracy of contrast-enhanced FLAIR (CE-FLAIR) and contrast-enhanced T1WI (CE-T1WI) in the detection of meningeal abnormalities in suspected cases of meningitis.

Results

Out of 45 patients, 37 patients were confirmed to have meningitis on CSF analysis. Out of the 37 patients, 34 patients were positive on CE-FLAIR sequence and 27 were positive on CE-T1WI. The sensitivity of CE-FLAIR sequence was 91.9% and specificity 100%, while the sensitivity of CE-T1WI sequence was 73% and specificity 100%.

Conclusion

CE-FLAIR is more sensitive than CE-T1WI in diagnosis of meningitis. It is recommended to be used in any cases with clinically suspected meningitis.

Signal intensity pattern of the normal oculomotor nerve on contrast-enhanced 3D FLAIR at 3.0 T MRI

PURPOSE

The aim of this study was to depict the signal intensity pattern of the normal oculomotor nerve demonstrated on contrast-enhanced three-dimensional fluid-attenuated inversion recovery images.

MATERIALS AND METHODS

Eighty-one patients were included in the study. Contrast-enhanced three-dimensional fluid-attenuated inversion recovery images with magnetisation-prepared rapid acquisition were reconstructed and evaluated in the coronal plane. The signal intensity of the cisternal segment of the oculomotor nerve was graded into a visual scale of 1 to 5 as compared to the white matter, grey matter and the pituitary stalk. The signal intensity ratio of the oculomotor nerve was consequently measured.

RESULTS

By using the visual scale, more than half of the oculomotor nerves showed higher signal intensity than the grey matter signal on contrast-enhanced three-dimensional fluid-attenuated inversion recovery images (59.3-80.2%). It can demonstrate a signal intensity similar to the pituitary stalk (14.8%) by visualisation. None of them showed signal intensity equal to the normal white matter signal. By signal intensity measurement, the mean signal intensity ratio of oculomotor nerves to white matter equals 1.54±0.20 (95% confidence interval (CI) 1.51-1.57); mean signal intensity ratio to grey matter equals 1.16±0.15 (95% CI 1.14-1.18); mean signal intensity ratio to the pituitary stalk equals 0.68±0.10 (95% CI 0.64-0.70).

CONCLUSIONS

The normal oculomotor nerve visualised on contrast-enhanced three-dimensional fluid-attenuated inversion recovery images has a higher signal intensity than the white matter and may have a signal intensity similar to the grey matter or the pituitary stalk. The high signal intensity of the oculomotor nerve in contrast-enhanced three-dimensional fluid-attenuated inversion recovery should not be misinterpreted as a pathology.

Noninvasive Characterization of Human Glymphatics and Meningeal Lymphatics in an in vivo Model of Blood-Brain Barrier Leakage

OBJECTIVE

To evaluate human glymphatics and meningeal lymphatics noninvasively.

METHODS

This prospective study implemented 3-dimensional (3D) isotropic contrast-enhanced T2 fluid-attenuated inversion recovery (CE-T2-FLAIR) imaging with a 3T magnetic resonance machine to study cerebral glymphatics and meningeal lymphatics in patients with reversible cerebral vasoconstriction syndrome (RCVS) with (n = 92) or without (n = 90) blood-brain barrier (BBB) disruption and a diseased control group with cluster headache (n = 35). The contrast agent gadobutrol (0.2mmol/kg [0.2ml/kg]) was administered intravenously in all study subjects.

RESULTS

In total, 217 patients (182 RCVS, 35 cluster headache) were analyzed and separated into 2 groups based on the presence or absence of visible gadolinium (Gd) leakage. Para-arterial tracer enrichment was clearly depicted in those with overt BBB disruption, while paravenous and parasinus meningeal contrast enrichment was evident in both groups. Paravenous and parasinus contrast enrichment remained in RCVS patients in the remission stage and in cluster headache patients, suggesting that these meningeal lymphatic channels were universal anatomical structures rather than being phase- or condition-specific. Additionally, we demonstrated nodular leptomeningeal enhancement in 32.3% of participants, which might represent potential lymphatic reservoirs. Four selected RCVS patients who received consecutive contrasted 3D isotropic FLAIR imaging after gadobutrol administration showed that the Gd persisted for at least 54 minutes and was completely cleared within 18 hours.

INTERPRETATION

This large-scale in vivo study successfully demonstrated the putative human para-arterial glymphatic transports and meningeal lymphatics by clear depiction of para-arterial, parasinus, and paravenous meningeal contrast enrichment using high-resolution 3D isotropic CE-T2-FLAIR imaging noninvasively; this technique may serve as a basis for further studies to delineate clinical relevance of glymphatic clearance. ANN NEUROL 2021;89:111-124.

Leptomeningitis in rheumatoid arthritis

In this case report, we describe the case of a patient given the presumptive diagnosis of rheumatoid leptomeningitis on the basis of clinical findings and clinical response to antirheumatic medications after other causes of meningitis were excluded. Numerous case reports describe rheumatoid meningitis; however, rheumatoid leptomeningitis, in the absence of pachymeningitis, is a rare phenomenon. As such, the literature about it is scant. This unique case provides an opportunity to further characterize the symptoms and radiological findings of leptomeningitis in a patient with rheumatoid arthritis.

Pre-clinical dose-ranging efficacy, pharmacokinetics, tissue biodistribution, and toxicity of a targeted contrast agent for MRI of amyloid deposition in Alzheimer's disease

In these preclinical studies, we describe ADx-001, an Aβ-targeted liposomal macrocyclic gadolinium (Gd) imaging agent, for MRI of amyloid plaques. The targeting moiety is a novel lipid-PEG conjugated styryl-pyrimidine. An MRI-based contrast agent such as ADx-001 is attractive because of the lack of radioactivity, ease of distribution, long shelf life, and the prevalence of MRI scanners. Dose-ranging efficacy studies were performed on a 1 T MRI scanner using a transgenic APP/PSEN1 mouse model of Alzheimer's disease. ADx-001 was tested at 0.10, 0.15, and 0.20 mmol Gd/kg. Gold standard post-mortem amyloid immunostaining was used for the determination of sensitivity and specificity. ADx-001 toxicity was evaluated in rats and monkeys at doses up to 0.30 mmol Gd/kg. ADx-001 pharmacokinetics were determined in monkeys and its tissue distribution was evaluated in rats. ADx-001-enhanced MRI demonstrated significantly higher (p < 0.05) brain signal enhancement in transgenic mice relative to wild type mice at all dose levels. ADx-001 demonstrated high sensitivity at 0.20 and 0.15 mmol Gd/kg and excellent specificity at all dose levels for in vivo imaging of β amyloid plaques. ADx-001 was well tolerated in rats and monkeys and exhibited the slow clearance from circulation and tissue biodistribution typical of PEGylated nanoparticles.

A New Tumor Delineation Method for Brain Metastases Radiotherapy by Jointly Referring to Contrast-Enhanced T1-Weighted and Fluid-Attenuated Inversion Recovery MRI

A new tumor delineation technique for brain metastases has been proposed by jointly referring to thin-slice contrast-enhanced T1-weighted and thin-slice contrast-enhanced fluid-attenuated inversion recovery magnetic resonance (MR) images. A single-isocenter six-arc noncoplanar volumetric modulated arc radiotherapy (VMAT) plan for 16 brain metastases was created by the Monaco treatment planning system (Elekta AB, Stockholm, Sweden) with a photon energy of 6 MV. Each gross target volume (GTV) was very carefully delineated on all three orthogonal planes of the above two different MR images. A dose of 37.5 Gy was prescribed to 96% of the whole brain in 15 fractions with a simultaneous integrated boost (SIB) dose of 57 Gy to 95% of each of the eight GTVs each having a volume larger than 0.05 cm³ and another SIB dose of 52.5 Gy to 90% of each of the remaining eight smaller GTVs. For accurate tumor localization, an in-house thermoplastic mask was developed by modifying a commercial thermoplastic shell, in such a way that a portion of the thermoplastic shell was pushed into a patient mouth so that the patient can bite it with the lips and the teeth. The outer cylinder of a syringe was additionally pushed into the resulting mouthpiece portion, thereby providing an air duct for easier mouth breathing. Immediately before the VMAT delivery, bone matching was performed between planning CT and on-board cone-beam CT images; thereafter, a six-degrees-of-freedom couch was activated to correct the translational and rotational set-up errors. The treatment time per fraction was approximately 30 minutes including the couch rotations.

-----Comparison of T1-Post and FLAIR-Post MRI for identification of traumatic meningeal enhancement in traumatic brain injury patients

Traumatic meningeal enhancement (TME) is a novel biomarker observed on post-contrast fluid-attenuated inversion recovery (FLAIR) in patients who undergo contrast-enhanced magnetic resonance imaging (MRI) after suspected traumatic brain injury (TBI). TME may be seen on acute MRI despite the absence of other trauma-related intracranial findings. In this study we compare conspicuity of TME on FLAIR post-contrast and T1 weighted imaging (T1WI) post-contrast, and investigate if TME is best detected by FLAIR post-contrast or T1WI post-contrast sequences. Subjects selected for analysis enrolled in the parent study (NCT01132937) in 2016 and underwent contrast-enhanced MRI within 48 hours of suspected TBI. Two blinded readers reviewed pairs of pre- and post-contrast T1WI and FLAIR images for presence or absence of TME. Discordant pairs between the two blinded readers were reviewed by a third reader. Cohen's kappa coefficient was used to calculate agreement. Twenty-five subjects (15 males, 10 females; median age 48 (Q1:35-Q3:62; IQR: 27)) were included. The blinded readers had high agreement for presence of TME on FLAIR (Kappa of 0.90), but had no agreement for presence of TME on T1WI (Kappa of -0.24). The FLAIR and T1WI scans were compared among all three readers and 62% of the cases positive on FLAIR could be seen on T1WI. However, 38% of the cases who were read positive on FLAIR for TME were read negative for TME on T1WI. Conspicuity of TME is higher on post-contrast FLAIR MRI than on post-contrast T1WI. TME as seen on post-contrast FLAIR MRI can aid in the identification of patients with TBI.

Ultrasound neuromodulation: mechanisms and the potential of multimodal stimulation for neuronal function assessment

Focused ultrasound (FUS) neuromodulation has shown that mechanical waves can interact with cell membranes and mechanosensitive ion channels, causing changes in neuronal activity. However, the thorough understanding of the mechanisms involved in these interactions are hindered by different experimental conditions for a variety of animal scales and models. While the lack of complete understanding of FUS neuromodulation mechanisms does not impede benefiting from the current known advantages and potential of this technique, a precise characterization of its mechanisms of action and their dependence on experimental setup (e.g., tuning acoustic parameters and characterizing safety ranges) has the potential to exponentially improve its efficacy as well as spatial and functional selectivity. This could potentially reach the cell type specificity typical of other, more invasive techniques e.g., opto- and chemogenetics or at least orientation-specific selectivity afforded by transcranial magnetic stimulation. Here, the mechanisms and their potential overlap are reviewed along with discussions on the potential insights into mechanisms that magnetic resonance imaging sequences along with a multimodal stimulation approach involving electrical, magnetic, chemical, light, and mechanical stimuli can provide.

Imaging of intratumoral heterogeneity in high-grade glioma

High-grade glioma (HGG), and particularly Glioblastoma (GBM), can exhibit pronounced intratumoral heterogeneity that confounds clinical diagnosis and management. While conventional contrast-enhanced MRI lacks the capability to resolve this heterogeneity, advanced MRI techniques and PET imaging offer a spectrum of physiologic and biophysical image features to improve the specificity of imaging diagnoses. Published studies have shown how integrating these advanced techniques can help better define histologically distinct targets for surgical and radiation treatment planning, and help evaluate the regional heterogeneity of tumor recurrence and response assessment following standard adjuvant therapy. Application of texture analysis and machine learning (ML) algorithms has also enabled the emerging field of radiogenomics, which can spatially resolve the regional and genetically distinct subpopulations that coexist within a single GBM tumor. This review focuses on the latest advances in neuro-oncologic imaging and their clinical applications for the assessment of intratumoral heterogeneity.

Reversible Cerebral Vasoconstriction Syndrome Presenting as Transient Vessel Wall Enhancement on Contrast-Enhanced Fluid-Attenuated Inversion Recovery Images: A Case Report and Literature Review

Reversible cerebral vasoconstriction syndrome (RCVS) is a clinical and radiological syndrome with primary features that include hyperacute onset of severe headache and segmental vasoconstriction of the cerebral arteries, which resolve within 3 months. Vessel wall enhancement has been reported in some cases of RCVS; however, its pathophysiological and diagnostic implications remain unclear. We review a case of RCVS in a patient with transient vessel wall enhancement on contrast-enhanced fluid-attenuated inversion recovery images, focusing on the pathophysiological and diagnostic implications.

Clinical Perspective on Primary Angiitis of the Central Nervous System in Childhood (cPACNS)

Non-arteriosclerotic arteriopathies have emerged as important underlying pathomechanism in pediatric arterial ischemic stroke (AIS). The pathogenesis and classification of cerebral arteriopathies in childhood are heterogeneous. Different classifications base on (i) the anatomic site; (ii) the distribution and size of the affected vessel; (iii) the time course, for example, transient vs. progressive, monophasic vs. recurrent; (iv) the putative pathogenesis; (v) the magnetic resonance imaging morphology of the vasculopathies. Inflammation affecting the cerebral vessels is increasingly recognized as common cause of pediatric AIS. Primary cerebral vasculitis or primary angiitis of the central nervous system (CNS) in childhood (cPACNS) is an important differential diagnosis in pediatric AIS. Primary angiitis of the CNS is a rare disorder, and the pathogenesis is poorly understood so far. The current classification of cPACNS is based on the affected cerebral vessel size, the disease course, and angiographic pattern. Two large subtypes are currently recognized comprising large- and medium-sized vessel CNS vasculitis referred to as angiography-positive cPACNS and angiography-negative small vessel cPACNS. As the clinical manifestations of cPACNS are rather diverse, precise diagnosis can be challenging for the treating pediatrician because of the lack of vital laboratory tests or imaging features. Initial misdiagnosis is common because of overlapping phenotypes and pediatric AIS mimics. As untreated cPACNS is associated with a high morbidity and mortality, timely diagnosis, and induction of immunomodulatory and symptomatic therapy are essential. Survival and neurological outcome depend on early diagnosis and prompt therapy. Primary angiitis of the central nervous system in childhood differs in several aspects from primary cerebral angiitis in adults. The aim of this article is to give a brief comprehensive summary on pediatric primary cerebral vasculitis focusing on the clinical perspective regarding the classification, the putative pathogenesis, the disease course, the diagnostic tools, and emerging treatment options. A modified terminology for clinical practice is discussed.

The neurocritical care of tuberculous meningitis

Tuberculous meningitis is the most severe form of tuberculosis and often causes critical illness with high mortality. Two primary management objectives are reducing intracranial pressure, and optimising cerebral perfusion, while killing the bacteria and controlling intracerebral inflammation. However, the evidence base guiding the care of critically ill patients with tuberculous meningitis is poor and many patients do not have access to neurocritical care units. Invasive intracranial pressure monitoring is often unavailable and although new non-invasive monitoring techniques show promise, further evidence for their use is required. Optimal management regimens of neurological complications (eg, hydrocephalus and paradoxical reactions) and of hyponatraemia, which frequently accompanies tuberculous meningitis, remain to be elucidated. Advances in the field of tuberculous meningitis predominantly focus on diagnosis, inflammatory processes, and antituberculosis chemotherapy. However, clinical trials are required to provide robust evidence guiding the most effective supportive, therapeutic, and neurosurgical interventions for tuberculous meningitis that will improve morbidity and mortality.